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MPH Part 2: Dosage, side effects, contraindications


MPH Part 2: Dosage, side effects, contraindications

66% of ADHD-HI and ADHD-C subtype children require moderate to high dosing.12
The “last 10 mg” are particularly important in order to achieve an optimum effect.3
When adjusting the dosage, the increase in dosage should therefore not be stopped too early. Emotional depletion (“zombie”) is a sign of overdosing.

Adults require a significantly lower dosage, as the number of DAT (dopamine transporters) decreases with age. The number of DAT is halved in 50-year-olds compared to 10-year-olds; for adults, an initial dosage of max. 5 mg every 3 hours (unretarded) is recommended.

The half-life of MPH is:4

  • for children approx. 2.5 hours
  • for adults approx. 3.5 hours

6. Dosage of MPH

6.1. MPH by weight?

Methylphenidate is not dosed across the board “according to body weight”. Some sufferers manage with very low doses of MPH (3 to 5 mg every 3 hours). Others need the maximum recommended dose of 1 mg/kg body weight per day.
The maximum dose of 1 mg/kg body weight per day applies primarily to children. A comprehensive meta-study of 28 cohort studies on 5524 children and adolescents up to 18 years of age, in which the appropriate MPH dose was determined in stages, reported a range from 0.8 mg/kg/day to 1.8 mg/kg/day.5 In patients who tolerate MPH well and achieve only a moderate effect with lower doses, a dosage of more than 1 mg/kg/day can also be tested.6

For adults (with a higher body weight), the required daily dose is usually significantly lower.

lower dosage for adults

Adults have far fewer dopamine transporters and therefore generally require less MPH than children. A dosage similar to that used in children can therefore already constitute an overdose in adults. For this reason, an even slower dosage in even lower increments (increase 2.5 mg to max. 5 mg unretarded/day, every 4 days) is recommended for adults. An overdose can cause exactly the symptoms that should actually be avoided, as the optimum dopamine level is already exceeded, which causes very similar signal transmission problems to the low dopamine level typical of ADHD. At a higher dosage (over 60 mg/day), individual neurologists report adaptation effects (not statistically proven).

6.2. Daily coverage MPH

In any case, it is advisable to use MPH to cover the entire day, but not the late evening and night.


Taking MPH only once (in the morning) for 3 (unretarded) or 6 hours (retarded) means that the person concerned is then at the mercy of their stress sensitivity again. MPH should be used with caution in the last few hours before going to bed. Most people react with sleep problems. For some, however, a quarter to half dose of stimulants enables them to fall asleep because it stops their thoughts from racing. It is possible that a low dose of unretarded stimulants could be helpful for people who already have low arousal. These are people who, for example, find it helpful to have a radio or television playing in the background to help them concentrate better. For others, listening to audio books helps them to fall asleep. People with a high arousal tend to need absolute quiet in order to be able to concentrate.

For the different duration of action of the individual MPH drugs, see below under 7.

6.3. Dosage adjustment of methylphenidate

6.3.1. Slow dosing in small steps

Slow and patient dosing is important. In our opinion, the usual dosing practice in Germany is far too fast.
In principle, MPH should be dosed low at the start of the test and the dosage should only be increased slowly. Even if the optimal dosage were known, an immediate optimal dosage would possibly lead to excessive demands7 and side effects.8

The dosage setting should start with 2.5 mg to a maximum of 5 mg / 3-4 hours, which should only be increased to 3 x 5 = 15 mg / day within the first few days. Tests with higher starting dosages not only produced no better, but even worse efficacy results and at the same time resulted in a significantly higher discontinuation rate due to side effects.8 Others recommend 2.5 to 5 mg twice daily, with a weekly increase of 2.5 to 5 mg.697810 Since such small dosage increments do not harm other patients (on the contrary, they help to avoid side effects), dosage increments in 2.5 mg steps (based on an unretarded single MPH dose) should be the gold standard. So does Kühle. A large meta-study points in the same direction. Other sources recommend starting with 1-2 single doses of 5 mg and increasing the single dose weekly in 5 mg increments. For the reasons mentioned, we consider these dose increments to be too large.11101213
A pharmacy in Switzerland offers MPH drops for sufferers for whom even extremely small differences in dose are crucial. One drop contains 0.35 mg MPH. It is produced in batches and preserved using E216 and E218.14 One patient reported that dissolving unretarded MPH in alcohol in such exact quantities that they could be measured out per drop showed a comparable result.

  • Inform those affected and observing third parties about the duration of action of the respective preparation and the expected rebound.
  • We consider a dosage increase of 2.5 mg per single dose every 5 to 7 days to be sensible. We now consider dosage increments of 5 mg / single dose, as we used to consider acceptable here, to be too high, because there is a relevant proportion of patients for whom 2.5 mg less means underdosing and 2.5 mg more means overdosing.10 Even if this only represents a minority of those affected, it would be malpractice to increase the dosage more quickly, as it is never possible to predict which group an affected person belongs to. See also below: Gene variants influence MPH dosage.
    The younger a patient is and the less they notice the MPH dose at all, the sooner the dosage increments can be increased.
    In the course of adjustment, the dose is increased until the characteristics of an overdose are intensified with the next and subsequent dose increases. The dose that optimally reduces the symptoms without causing side effects can then be determined.
    Unfortunately, there are known cases in which doctors have started discontinuation with single doses of 15 or 20 mg. We strongly advise against this.
    Even if this were the right dosage for a small number of patients, the risk of suffering considerably more severe side effects in the first few weeks with such a high starting dosage would be significantly higher than with a slower adjustment.

6.3.2. No caffeine with MPH dosage

Caffeine (theine is also caffeine), theobromine (dark cocoa) and other stimulants should be avoided at all costs when dosing. Caffeine, which was previously tolerated without any problems, can suddenly trigger internal tremors and other symptoms when taken simultaneously with stimulants, which can then be misinterpreted as a side effect of the medication. When new doses of stimulants are taken, caffeine can trigger a sensation similar to an overdose. Once the stimulants have been dosed, caffeine can be tried again. Sensations of discomfort can then be correctly attributed to caffeine.

6.3.3. No nicotine withdrawal with MPH dosing

Nicotine withdrawal started at the same time as dosing can falsify the result. The need for cigarettes often decreases of its own accord after taking stimulants.
Similarly, restarting nicotine intake during stimulant dosing should be avoided.

6.3.4. Age-related differences in dosage

As adults have significantly fewer dopamine transporters than children (50-year-olds have only half as many as 10-year-olds,15 a much lower dosage is indicated for adults than for children.

More on this at Dosing of medication for ADHD.

6.3.5. Gene variants influence MPH levels

A small proportion of those affected require a significantly lower dosage of MPH.

The CES1 polymorphism Gly143Glu was found in 5.8% of ADHD sufferers and 4.1% of the population. No cases of CES1 Glu143Glu (homozygous) were found among 441 children.
CES1 Gly143Glu showed an unchanged reduction in inattention and hyperactivity-impulsivity on MPH.
Carriers of the CES1 143Glu variant (5.56%) required almost 30% lower doses of MPH to reduce symptoms.16

More on the influence of CES1 gene variants on the effect of MPH at Influences on the potency of MPH In the article MPH Part 3: Degradation, potency.

6.4. Side effects when discontinuing methylphenidate

In the first few days, taking the medicine can feel like snow has fallen - everything is wrapped in absorbent cotton. This (usually very pleasant) impression is due to the reduction in sensory overload and, like most side effects, disappears within a few days.
Side effects such as headaches, sleep problems or others occur rarely. Most side effects subside within the first few weeks after dosing. The risk of such side effects can be considerably reduced by very slow dosing (as described above).8 Headaches can sometimes be reduced or avoided by drinking enough and eating regularly (possibly glucose). As stimulants reduce the feeling of hunger, this can contribute to reduced fluid and food intake, which can also cause headaches.

One study found that MPH did not cause sleep problems. This could differ from the results of other studies possibly because this study lasted a relatively long 16 weeks, so that the acclimatization side effects were no longer noticeable.17 In contrast, a small study that only looked at 14 days found reduced sleep duration and delayed sleep onset in children treated with sustained-release MPH.18

6.5. Overdose symptoms with MPH

With an appropriate dosage of MPH, the ability to concentrate increases and the internal pressure and any hyperactivity present decrease. If the latter increases again when the dosage is increased, this is a sign that the dosage is too high.
Methylphenidate closes the stimulus filter (which is too wide open in ADHD sufferers). A typical reaction of those affected with the right dosage is that they come to themselves, that they are more themselves.

If the person concerned notices that MPH makes them jittery (even though neither caffeine (theine is just another name for caffeine) nor theobromine (dark cocoa) is consumed), the dose should still be increased carefully at first. It has been observed several times that such side effects disappear again after a few days or at the next higher dose. If this shakiness persists, the dosage is too high. This also applies if the concentration becomes too high, i.e. the stimulus filter is restricted too far. Restricted emotionality (“zombie effects”) is a clear indication of an overdose.

A study on monkeys concluded that low doses of MPH reduce impulsivity, while higher doses have a sedative effect.19
This follows on from empirical experience that ADHD sufferers, especially children, can sometimes appear apathetic when taking MPH. Following this study, this indicates an overdose.

6.6. Try different MPH medications even if MPH is effective, especially in the case of side effects / non-responding

Many patients report that they experience side effects with one MPH preparation that they do not experience with another MPH preparation. There are reports on this side that one MPH preparation (here: Medikinet) showed no effect, while another (here: Concerta) responded well.
Other sufferers report that they had to contend with increased aggression in response to one preparation (here: Concerta), which did not occur with another MPH preparation (Medikinet or unretarded MPH).
Others experience a stronger rebound effect with Medikinet (increase in agitation when the effect wears off) than with other MPH preparations.

The various MPH preparations have very different release times, and MPH is embedded in different carriers depending on the manufacturer.
In the case of an existing gluten intolerance, MPH embedded in wheat starch is naturally unsuitable. The same may apply to lactose intolerance.

If a satisfactory effect is not achieved with all MPH preparations (the typical non-responder rate is just under 30%), medication with amphetamine drugs should always be used. As a result, a further 70 to 80 % of MPH non-responders can be satisfactorily medicated, so that the overall non-responder rate for MPH and AMP falls to below 10 %.
If dysthymia or depression persists despite the satisfactory effect of MPH, a switch to amphetamine medication can also be considered, as these also have a mild serotonergic effect.

Antidepressant effects were observed at MPH daily doses of 10 to 30 mg and at AMP daily doses of 5 to 60 mg.6

6.7. Accompanying circumstances of recruitment and intake

Some patients always need their MPH medication at exactly the same time.
Care should be taken to ensure that the entire day is covered. However, the last doses of the day must be taken early enough so that there is no effect at bedtime.


During the adjustment to MPH, caffeine (coffee, black tea), theobromine (dark cocoa) and alcohol should be completely avoided, as these can increase the effect of stimulants. Many sufferers report that MPH makes them much more sensitive to such stimulants. A jitteriness can therefore be triggered by caffeine, whereas the same amount of caffeine without MPH had no such effect. Like antidepressants, MPH often causes mild side effects (dry mouth etc.) in the first few days or weeks of taking it, which soon subside.

To prevent or alleviate loss of appetite, it is recommended to take it with or after meals.

6.8. Effect on those not affected

MPH can also have an effect on non-ADHD sufferers. It can (in low doses) increase attention, just as mild stress increases cognitive performance by slightly increasing noradrenaline and dopamine in the PFC.
A higher dosage in people who are not affected (such as a low dosage in people who already have slightly elevated dopamine or noradrenaline levels) can cause such a strong increase in DA and NE levels that ADHD symptoms are triggered.
In ADHD, the (tonic) dopamine level in the striatum is too low, which causes a number of ADHD symptoms. MPH increases the dopamine level in the striatum to the optimum level when dosed correctly. However, if the dopamine level is increased beyond the optimal level - by overdosing in ADHD sufferers or by taking MPH in healthy people - this triggers the same symptoms as in ADHD, because neurotransmitter communication only functions optimally at the correct neurotransmitter level.20

The increase in dopamine in the dorsal striatum (but not in the nucleus accumbens) following amphetamine administration is higher in both male and female rats if they have previously been exposed to chronic uncontrollable stress. This could indicate a different dopaminergic response to stimulants (ADHD medication) in those affected by chronic stress such as ADHD.21

6.9. MPH in senior citizens

There is no explicit restriction on the approval of methylphenidate for the elderly. The MPH product information contains a note that MPH should not be prescribed to older people. There is no such indication for lisdexamfetamine, despite equally inadequate data.
Treatment with MPH at an older age should nevertheless be able to constitute an offlabel prescription.22

There are no indications that MPH would cause difficulties in old age.
A small study reported good tolerability in older patients.23

7. Retarded or unretarded MPH

This section has been moved to Retarded MPH, Retard techniques In the article MPH Part 3: Retardation

8. Carrier substances

  • Ritalin: wheat starch7
  • Medikinet: corn starch7
  • Equasym: Lactose (milk sugar)7

9. Quality of effect of methylphenidate

Methylphenidate is the drug of choice for children. It combats the symptoms of ADHD significantly better than one year of behavioral therapy. Comparable effects are only achieved after 3 years of behavioral therapy.

Since stimulants establish or increase the ability to learn and engage in therapy, it makes sense to initially work acutely with stimulants in order to create the basis for discontinuing them in parallel by means of behavioral therapy and/or neurofeedback.

The mean effect size of MPH for ADHD is between 0.9 and 1.3.

For the effectiveness of individual medications and forms of treatment, see Effect strength of various forms of ADHD treatmentin the chapterTreatment and therapy.

MPH medication in combination with noradrenergic medication or zinc can further improve the effect. However, a cautious approach is recommended here. It is advisable to consult a doctor with experience in ADHD medication.

10. Side effects of methylphenidate

Most side effects only occur shortly after starting the medication and usually disappear within the first four weeks. The short-term feeling of a dry / furry tongue after taking the medication may last longer.
Tic disorders are observed with overdoses. If those affected have the feeling for months that the world is moving away or that life is becoming monotonous, this is also a clear indication of overdose.
At an appropriate dosage, the effect of MPH gives ADHD sufferers the feeling that they are much more themselves than before. If a sufferer has the feeling that stimulants make them less themselves, this is a very serious indication of incorrect dosing, misuse or misdiagnosis.

Several studies have found that adverse reactions to stimulants occur primarily in patients with higher anxiety levels and faster reaction times or pre-existing comorbidities.2425
No correlation with EEG values was found.25
A systematic review found no serious side effects of long-term MPH use.26

10.1. Growth in length delayed for a short time

Several comprehensive studies have found no persistent impairment of longitudinal growth in boys with ADHD due to MPH.27

A temporary impairment of longitudinal growth in the first year of MPH treatment was recovered in the second year.28 Temporary impairment of longitudinal growth is common in ADHD in childhood and is regularly recovered in adolescence. This is apparently not a specific effect of methylphenidate.29 Another study found a 4-fold increased risk of reduced length growth and weight gain in children with ADHD aged 8 and 10 years. The length of stimulant treatment increased this risk.30

10.2. Slight weight loss

One comprehensive study found a slightly lower BMI in boys with ADHD on MPH.27 In another study, the weight reduction due to MPH was only trended and not statistically significant.28 A large meta-analysis of 38 cohort studies on 5524 participants up to 18 years of age found weight loss with an OR of 5.11 compared to placebo.5

10.3. Blood pressure unchanged

A comprehensive study found no adverse effect of MPH on blood pressure in boys with ADHD.31

10.4. Liver damage not known

No increased reports of liver damage are known with MPH.32 However, liver values should always be monitored when discontinuing ADHD medication.

10.5. Reduced risk of stress fractures

MPH use by ADHD sufferers reduced the risk of stress fractures compared to non-affected persons (without MPH use).33

10.6. More common mild side effects

A large meta-analysis of 38 cohort studies involving 5524 participants up to 18 years of age found the most common side effects to be sleep problems (OR 4.66), weight loss (OR 5.11), abdominal pain (OR 1.9) and headaches (in 14% of MPH takers) compared to placebo.5 Sleep problems are often caused by dosing too late in the day, especially when starting dosing. Very slow dosing can help to avoid side effects. Most of these side effects disappear within the first few weeks.
For some people, the administration of a small unretarded dose (1/4 to 1/2 of a single daily dose) helps them to fall asleep.6
A study that lasted 16 weeks found that MPH did not cause sleep problems.17 However, a small study lasting only 14 days found reduced sleep duration and delayed sleep onset in children treated with sustained-release MPH.18 This is consistent with the experience that sleep problems are possible with MPH, but are usually only a side effect of dosing. We conclude that in case of sleep problems due to MPH during the first weeks, it might be helpful to shorten the daytime coverage. Irrespective of this, slow dosing in steps of max. 2.5 mg / single dose of unretarded MPH is always recommended.

One study reported a statistically significant increase in intraocular pressure only in the left eye due to MPH in ADHD. A change in the thickness of the macular, retinal nerve fiber layer (RNFL) or ganglion cell layer (GCL) was not reported.34

10.7. Parkinson’s / Tremor in old age

A very comprehensive study analyzed the probability of Parkinson’s type disorders (simple tremor to Parkinson’s) in ADHD sufferers with and without stimulant use over decades of their lifetime.35

The results of the study are extremely interesting:

  1. ADHD increases the lifetime likelihood of a Parkinson’s (-like) disorder by 2.4 times
  2. Parkinson’s (-like) disorders are even more likely if the ADHD sufferers had taken stimulants (6-fold)
  3. Parkinson’s (-like) disorders are 8 times more common in ADHD sufferers who were given methylphenidate than in non-affected people

It should be noted:

  1. The result contradicts a later long-term study (see below).
  2. The correlation is correct
  3. Causality is questionable
    Is Parkinson’s more likely in stimulant users or in more severe ADHD, which is more often treated with stimulants?
    The study design does not allow a statement on this. Other studies will be needed for this.
  4. The increased risk of comorbidity in ADHD is not limited to Parkinson’s disease.
    The probability of early death is drastically increased with untreated ADHD: from 0.8% for those without ADHD to 2.3% for those with ADHD, i.e. plus 1.5 percentage points

The absolute figures are more revealing.
A disorder of the basal ganglia or cerebellum (a disorder related to Parkinson’s (tremor) or Parkinson’s disease) was diagnosed

  • 56 of 24,792 non-ADHD sufferers = 0.23 %

    • Of which 26 = 0.1 % with less than 50 years of age
    • Of which 19 = 0.08 % developed Parkinson’s disease
  • 104 of 26,809 ADHD sufferers who were not known to be receiving stimulants = 0.39 %

    • Of which 69 = 0.26 % with less than 50 years
    • Of which 38 = 0.14 % developed Parkinson’s disease
  • 62 of 4960 ADHD sufferers who were known to be taking stimulants = 1.25 %

    • Of which 42 = 0.85 % with less than 50 years
    • Of which 19 = 0.38 % developed Parkinson’s disease

60% of stimulant users had taken amphetamines and 40% had taken methylphenidate. If the risk is 6-fold higher for all stimulant users and 8-fold higher for MPH, which was taken by only 40%, it must therefore be significantly lower than 4-fold for amphetamine drugs.

This means that the risk of a Parkinson’s (related) disorder could be estimated to be

  • 1 % for ADHD, treated with amphetamine medication
  • 2 % for ADHD, treated with methylphenidate

One could also - just as correctly - formulate this:
The risk of developing a Parkinson’s (related) disorder within 20 years is increased by 0.16 percentage points in people who have ADHD (0.16% more people develop a Parkinson’s (related) disorder if they have ADHD than if they do not). If amphetamine medication is taken, the increase is 1 percentage point higher compared to those who are not affected; if methylphenidate is prescribed, the risk is increased by 2 percentage points.

If you convert that to 100,000 people:

  • 1.5% of 100,000 are 1500 additional premature deaths due to ADHD
  • 1% of 100,000 is 1000 additional people affected by Parkinson’s type disorders (from a simple tremor to Parkinson’s) with amphetamine medication for ADHD (without knowing whether this is due to the severity of the ADHD or the AMP).
  • 2% of 100,000 are 2000 additional people affected by Parkinson’s type disorders (from a simple tremor to Parkinson’s) with methylphenidate for ADHD (without knowing whether this is due to the severity of the ADHD or the MPH).

But if someone who has ADHD has a choice,

  • With untreated ADHD tripled the risk of early death from 0.8% to 2.3% (absolute: plus 1.5 percentage points)
  • What medication can largely remedy
  • Or to accept an increased risk of Parkinson’s type disorders (from simple tremor to Parkinson’s disease) by a factor of three to eight, but in absolute terms only by 1 to 2 percentage points,

most people would prefer to have a trembling hand when alive than a steady one when dead.

It also follows that if ADHD can be treated with amphetamine medication, this should be preferred to MPH.

Against this background, the wording of the study results sounds somewhat tendentious or attention-seeking.
The study design would be perfect to show how much higher mortality is with medication. However, this - much more important - question is not answered, even though this data should have really jumped out at the authors. Similarly, no differentiation is made between the fact that the risk was only half as high with amphetamine medication as with methylphenidate, but only the higher figure for methylphenidate was mentioned.

The increase in the risk of Parkinson’s type disorders (from a simple tremor to Parkinson’s disease) due to chronic overdose of MPH could result from an increased production of quinones and a reduction of glutathione (GSH, γ-L-glutamyl-L-cysteinylglycine).36 Chronic administration of 10 mg MPH / kg (approximately 10 times the maximum therapeutic amount in humans) promoted a loss of dopaminergic cells in the substantia nigra.37 A loss of dopaminergic cells could explain Parkinson’s symptoms. This also indicates that high doses of MPH should be avoided if possible.

A German study found no evidence of a correlation between Parkinson’s and the use of psychostimulants such as methylphenidate in childhood.38

Another long-term study found that stimulant prescriptions for ADHD reduced the risk of Parkinson’s disease by 60%39

10.8. Slightly increased risk of psychosis?

According to a very large study, the risk of developing psychosis is lower for ADHD sufferers taking MPH (0.10%) than for those treated with amphetamine medication (0.21%).40 While ADHD sufferers treated with stimulants have 2.4 cases of psychosis per 1000 person-years (0.24%), the figure for the population as a whole is 0.0214%.41 The studies do not allow any conclusion to be drawn as to whether the increase in the prevalence of psychosis is due to the existence of ADHD or to the administration of stimulants. However, the doubling of the risk due to amphetamine medication compared to MPH preparations indicates this.

Another large study based on the Swedish health register with 23,898 adolescents and young adults with ADHD compared the risk of psychosis before and after MPH administration and found only a non-significant increase of 4% in the risk of psychosis due to methylphenidate.42 This is in line with another large cohort study, which found a significantly increased risk of psychosis in ADHD in general. Stimulants further increased this risk very slightly (6%), while the increase of 15% for non-stimulants was almost three times as high as for stimulants.43 If anything, high doses of MPH appear to increase the risk of psychosis.44

The benefits of treating ADHD (reduction in premature mortality, reduction in lifelong risk of depression and anxiety disorders, reduction in risk of addiction, etc.) clearly outweigh the potential risk.
More on the risks of (untreated) ADHD at Consequences of ADHD.

10.9. Increased risk of anorexia

Treatment with MPH increases the risk of anorexia by 4.66 times.45
Treatment with stimulants should therefore be avoided in patients with anorexia nervosa.

10.10. Cramp threshold lowered

Methylphenidate is said to be able to lower the seizure threshold. This applies to patients with an existing history of seizures (e.g. epileptics) as well as patients with abnormalities in the EEG without previous seizures. In rare cases, MPH can trigger seizures even without the aforementioned previous risks.
If the frequency of seizures increases or if new seizures occur, methylphenidate should be discontinued.46

10.11. Stimulation of existing anxiety disorders, depression, aggression

Comorbid anxiety disorders, depression and aggression can be exacerbated by stimulants, as anxiety and moods are regulated by the dopaminergic activity of the ventromedial PFC in conjunction with the limbic system. In these cases, noradrenaline reuptake inhibitors or α2A-adrenoceptor agonists are recommended instead.47
One (quite small) study found no short-term change in state anxiety with a single dose of MPH, but did find evidence of a possible long-term worsening.48

10.12. MPH and risk of mania in bipolar disorder

One study found that MPH was not associated with an increased risk of mania in patients with bipolar disorder. After MPH treatment, mania decreased by 50 %. Depressive episodes and psychiatric admissions also decreased.49

10.13. MPH increases histamine

MPH increases histamine,50 as do all other known ADHD medications:

  • Atomoxetine
  • Amphetamine
  • Modafinil
  • Nicotine
  • Caffeine

This is why people with histamine intolerance often have problems when taking ADHD medication.
An ADHD sufferer with histamine intolerance reported that she could not tolerate AMP and sustained-release MPH at all, but was able to tolerate low doses of sustained-release MPH.

10.14. No increased cardiovascular risks

The hypothesis that methylphenidate would cause increased heart problems was not confirmed.51 No changes in EEG values were found.25 A meta-study found slightly increased values below statistical significance.52

An initial study with n = 564 patients, which suspected an increased cardiac death rate in children taking MPH, was refuted by a number of other studies, including a large study with n = 241,417 children taking MPH.53 A very large study found no increased risk of serious cardiovascular events such as stroke, heart attack or cardiac arrhythmia for MPH among 2,566,995 children.54
There are also studies that even confirm a reduced risk of cardiac death under MPH, which can be explained by the medical care provided to those affected.

Several studies found no significant change in heart rate, QRS, QT, QTc and QTd interval in ECGs due to MPH.
The Tp-Te intervals and Tp-Te/QTc ratios were slightly increased after treatment with MPH, but within normal values.55 Children with ADHD showed significantly prolonged P-wave dispersion, TpTe interval, TpTe dispersion and TpTe/QT and TpTe/QTc ratios. In addition, almost half of the patients had QTc values of 460 ms or more. These parameters were neither associated with the MPH dose nor with the duration of treatment.56

One study found no increased risk of cardiac arrhythmias for methylphenidate. However, an increased risk of cardiac arrhythmia was found for atomoxetine for 7 days after the first exposure to atomoxetine (aIRR 6.22) and for subsequent exposure (aIRR 3.23).57
A study over 14 years found an increase in the risk of cardiovascular problems of 4% per year of taking stimulants (methylphenidate, amphetamine drugs) and, to a lesser extent, the non-stimulant atomoxetine.58

In adults, cardiovascular problems are said to be possible due to MPH.59

10.15. Rebound

A rebound is a short-term increase in symptoms that are actually reduced by MPH at the end of the medication’s effective period. If a dose of MPH works for around 3 hours, ADHD symptoms may increase for around 20 to 30 minutes at the end of the 3 hours or immediately afterwards.
Rebound is reported more frequently and more clearly with unretarded MPH than with retarded MPH.60
We assume that a rebound is caused by too rapid a decline in dopamine/noradrenaline levels. A rebound seems to occur less frequently with drugs that show a very slow decline in effect.

A rebound can be avoided by taking the follow-up dose in good time so that no drug-free period remains.
In the case of the last daily dose, the rebound should be mitigated or avoided by taking a much smaller dose than the usual single dose at the time when the subsequent dose would otherwise be taken.

10.16. Long-term effects of MPH

The reports known to us to date on the harmful effects of long-term use of MPH are all based on massive overdoses. Such studies are usually useful in order to sound out the limits of tolerability of an active substance. However, they say nothing about the dangers of long-term use at normal doses.
To put this into perspective: humans need 30 to 40 ml of water per kg per day (2 to 3 liters). however, 3 liters of water at once or 5 liters of water per day can already have a lethal effect. This means that even doubling the amount of water given to humans can have fatal effects.

A large-scale, long-term study on MPH over 2 years in children with ADHD found that the MPH group61

  • no significant impairment of growth
  • slight weight loss in the first 6 months, which then subsided
  • no change in relation to psychosis, depression, dyskinesia, tics
  • slightly elevated blood pressure and pulse
  • preventive effect in relation to addiction and suicide
    • significantly increased nicotine and marijuana use in the non-MPH group
    • significantly increased suicidal tendencies in the non-MPH group

A study in primates found no change in brain parameters 6 months after the end of 12 years of long-term administration of MPH.62

A study in adult rats found damage to the morphology and function of the cerebellum after long-term administration of 15 to 20 times the usual daily dose.63 This is as expected for such doses.

A study on rats that received 5 mg/kg/day, five times the maximum daily dose normally given to humans during puberty, found that sperm quality was impaired in the adult animals.64 These were also Wistar rats, i.e. rats that do not have a dopamine deficiency.
In hyperactivity sufferers, there was no statistically significant difference in sperm count after taking methylphenidate, but there was a significant difference in sperm motility and abnormality65

In one study, monkeys were given 2.5 mg/kg or 12.5 mg/kg MPH twice daily. 12.5 mg/kg twice daily is around 25 times the maximum dose usually recommended for humans and, in our view, represents a drug dose rather than a medication dose.
Apart from a temporary reduction in motivation after the end of MPH administration (again, only with the “drug dose”), no negative effects were found 66
At twice 12.5 mg/kg/day, there was also a significant deterioration in cognitive performance, as would be expected with such an overdose.67

10.17. MPH and narcosis / anesthesia

In the case of operations, in addition to the sometimes significantly increased (drug) sensitivity of ADHD sufferers, the question of cross-effects of ADHD drugs with anesthetics must also be considered.

A double-blind study from 1980 found no change in postoperative pain with MPH. Methylphenidate shortened postoperative sedation by up to 30 minutes and improved respiratory function by up to 180 minutes with halothane anesthesia.68 Halothane is no longer used today.
One case study reports a reduced response to sedatives and increased side effects due to MPH:69

One study reports a correlation between attention problems and postoperative delirium.70

10.18. Other side effects of MPH

Individual cases of trichotillomania (pulling out hair) have been reported.71 Trichotillomania is a specific form of impulse control disorder.
One study reported muscle pain and stiffness as a possible side effect of MPH.72
One study reported a doubled rate of testosterone deficiency in adult ADHD sufferers after 5 years of stimulant use (1.2%) compared to ADHD sufferers without stimulant use (0.67%) or non-affected individuals (0.68%).73

11. Interactions and contraindications

As with any medication, there are also contraindications for MPH.
Taking it without prior medical consultation is risky!

Methylphenidate is metabolized independently of the cytochrome P450 system, so that there is only a very low potential for pharmacokinetic interactions.46

11.1. Interactions of methylphenidate with other medications

11.1.1. Enhanced effect of other drugs / substances due to MPH

  • Caffeine can have a more intensive effect
    Caffeine should be strictly avoided, especially when taking stimulants (e.g. MPH). Stimulants often cause caffeine in doses that were previously tolerated without any problems to now trigger inner tremors. This can be wrongly interpreted as a (side) effect of the stimulants.
    A very high dose of caffeine (tens of times above drug level) over several days reduced the efficacy of MPH in rats, and vice versa. This confirms that MPH and caffeine have common,7475 but not identical76 mechanisms of action.

  • Alcohol
    A comprehensive meta-analysis found little evidence that ADHD medication in combination with alcohol or other drugs would have any particular negative effects.77

    • Taken together with MPH, alcohol can have a more intensive effect
    • Alcohol taken together with MPH can increase MPH levels78
  • All sympathomimetics79 can be strengthened by MPH.
    Active substances concerned:

  • Monoamine oxidase inhibitors (MAOI)

    • No monoamine oxidase inhibitors (MAOIs) should have been taken in the 14 days prior to taking MPH. Taking MAOIs and methylphenidate at the same time can result in a sudden increase in blood pressure.8046
      • St. John’s wort is a MAOI81 and also inhibits COMT.
        With regard to St. John’s wort, there are suspected interactions with MPH.82
      • Tranylcypromine
        MPH should be avoided for up to 14 days after taking tranylcypromine83
  • Antihypertensives46

  • Halogenated anesthetic gases

    • Can trigger blood pressure spikes in patients taking methylphenidate46 Methylphenidate should not be used on the day of surgery for planned surgical procedures.
  • All central dopaminergic and noradrenergic active substances46
    Blood pressure should be monitored closely in this case.

    • Moclobemide
    • Linezolid
    • Selegiline
    • Rasagiline
    • Levodopa
    • Other Parkinson’s remedies
    • Centrally acting α2 agonists, e.g.
      • Clonidine
      • Methyldopa

11.1.2. Inhibition of the metabolism of other drugs by MPH

  • Anticonvulsants84
    • Phenobarbital7985
    • Phenytoin7985
    • Primidone79
    • Carbamazepine
      • 2 individual case reports indicate that at least a doubling of the MPH dose may be necessary if high doses of carbamazepine are given at the same time85
    • Rifampin possibly85
      MPH reduces the effect of anticonvulsants79
      Anticonvulsants reduce the MPH blood level after a few weeks85
  • Tricyclic antidepressants46, e.g:
    • Amitriptyline79
    • Imipramine79
      Methylphenidate enhances the effect of imipramine,85 while imipramine also enhances the effect of MPH. Therefore, a particularly cautious dosage of imipramine with simultaneous MPH administration is recommended.
      Symptoms are:
      • Confusion and agitation
      • Mood instability
      • Irritability and aggressiveness
      • Psychotic symptoms
  • Phenylbutazone (Butazolidine)79
    Phenylbutazone is a non-steroidal anti-inflammatory drug that is rarely used today.
  • Anticoagulants (blood clotting inhibitors)79
    • Oral anticoagulants of the coumarin type, e.g. phenprocoumon, warfarin
      Fluctuations in effect are possible here due to interaction with methylphenidate. The mechanism is unknown. Close monitoring of coagulation parameters is therefore recommended when starting and stopping methylphenidate.46
  • Antihypertensives46, e.g:
    • ACE inhibitors
    • Angiotensin receptor blockers
    • Diuretics
    • Calcium channel blockers
    • Beta-blocker
  • Metoclopramide (prokinetic, dopamine antagonist)46

11.1.3. Changes in the effect of MPH due to other medications

An elevated gastric pH above 5.5 can accelerate / increase the release of the retarded components of Medikinet adult. However, the release of methylphenidate from Ritalin adult is pH-independent. Nevertheless, a reduction in absorption is possible with Ritalin adult due to antacids.46

The stomach pH value can be increased by:

  • Proton pump inhibitors, e.g.
    • Pantoprazole
    • Omeprazole
  • H2 antagonists (although less likely), e.g.
    • Ranitidine
    • Famotidine
  • Antacids

Chronic oral MPH alone produced a tendency in the striatum of rats to86

  • Increased dynorphin expression
  • Increased substance P expression
  • Unchanged enkephalin expression.

Oral fluoxetine alone did not change the expression of these genes.

MPH and fluoxetine together caused

  • Strongly increased dynorphin expression
  • Strongly increased substance P expression
  • Increased enkephalin expression

Oxytocin potentiates MPH-induced stimulation of tonic (extracellular) dopamine firing, probably by modulating dopamine receptor signaling pathways. Oxytocin did not affect MPH-induced dopamine reuptake or MPH-induced phasic dopamine firing.87

11.2. MPH and blood pressure

Methylphenidate can increase blood pressure in children.

In children with ADHD, blood plasma levels of nitric oxide appear to be increased and asymmetric dimethylarginine (ADMA) decreased. ADMA inhibits the blood pressure-increasing effect of nitric oxide. When MPH was taken, plasma nitric oxide levels increased further. This could possibly be due to a reduced inhibition of nitric oxide by ADMA during MPH administration and could be a cause of the blood pressure increasing effect of MPH.59
In contrast, a comprehensive study found no impairment of blood pressure in boys with ADHD due to MPH.31
Patients at risk of high blood pressure should therefore weigh up the extent to which the possible risk of a drug-induced increase in blood pressure outweighs the possible benefit of reduced blood pressure due to reduced sensitivity to stress.

11.3. MPH intake during pregnancy

One study found no reduction in the weight of newborns of mothers with ADHD who took amphetamine medication during pregnancy.88 This is consistent with results from a large cohort study of MPH use during pregnancy.89
Another comprehensive study found a slight reduction in birth weight and a slight increase in the risks of pre-eclampsia, placental abruption or premature birth with stimulant use (AMP or MPH) during pregnancy, although this was so small that the authors did not recommend discontinuing stimulant use during pregnancy.90 Atomoxetine did not show these slight increases in risk.
A Danish cohort study found a doubled risk of miscarriage when taking stimulants during pregnancy.91
Another Danish cohort study found a very small increase in malformations in children of mothers who had taken MPH in the first trimester of pregnancy. The authors described the increase in risk as not relevant.92 A smaller study found no increased risk.93

A meta-analysis of 4 cohort studies found a small but statistically significant increase in the risk of malformations and cardiac malformations in children whose mother had taken MPH in early pregnancy.94

A study on mice found increased ADHD symptoms in offspring when given MPH during pregnancy. A 2.5 to 15-fold dosage (compared to the usual maximum drug level) caused reduced expression of the D2 receptor and dopamine transporter genes, which are common in ADHD.95 This is plausibly consistent with the model of brain development disorders caused by a lack of dopamine (e.g. genetically inherited or due to chronic stress) or an excess of dopamine (e.g. due to stimulant administration in non-affected individuals). More on this at Brain development disorder and ADHD In the chapter Development.
A cohort study found no increased risk of ADHD or other neuronal developmental disorders due to MPH or AMP use during pregnancy. The increased ADHD risk initially found was due to the mothers’ ADHD on closer examination.96

12. Possible contraindications

Caution is advised when using methylphenidate for:46

  • Glaucoma
  • Hyperthyroidism
  • Thyrotoxicosis
  • Severe depression
  • Psychoses, e.g.
    • Schizophrenia
    • Mania
    • Bipolar disorder type I
  • Cardiomyopathies
    • Especially severe arrhythmias
  • Asthma97
  • Interstitial pneumonia or fibrosis97

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