Methylphenidate is a medication used mainly in the treatment of attention deficit hyperactivity disorder in children and adults.
In addition, it is used to treat narcolepsy in adults as a second-line option.
Off-label uses of methylphenidate include resistant depression in the elderly population, treatment for fatigue in patients with cancer, apathy in Alzheimer's disease, and enhancing cognitive performance, including memory.
Neurotransmitters are chemical molecules that allow nerve signal conduction through a synapse.
A synapse consists of pre-synaptic and post-synaptic terminals and the synaptic cleft.
When the nerve impulse reaches the pre-synaptic terminal, it releases neurotransmitters into the synaptic cleft, and they bind to the post synaptic membrane to transmit the nerve impulse.
Once the nerve impulse is transmitted thought the synapse, released neurotransmitters are taken up by the pre-synaptic terminal.
This is called the re-uptake of neurotransmitters.
Methylphenidate blocks the re-uptake of two neurotransmitters, norepinephrine, and dopamine, in presynaptic neurons.
This will increase the concentrations of dopamine and norepinephrine in the synaptic cleft, which creates a stimulant effect within the central nervous system, especially in the pre-frontal cortex.
Methylphenidate also slightly increases the activity of 5HT1A receptor, which also increases the levels of dopamine.
Since it increases the levels of dopamine in the brain, methylphenidate can provide neuroprotection in conditions like Parkinson disease.
Methylphenidate is taken per orally and it is readily absorbed into the blood.
A transdermal patch is also available, but it is not used frequently.
Oral tablet is available in immediate release, extended release, and sustained release forms.
Once in blood, methylphenidate is transported by plasma proteins.
It is metabolized in the liver by a process called de-esterification to ritalinic acid.
More than 75% of the drug is eliminated by the kidneys.
Insomnia and agitation are the commonest adverse effects of methylphenidate.
Central nervous system side effects such as dizziness and headache may also occur.
Gastro intestinal side effects include nausea and vomiting, diarrhea, abdominal pain, and dry mouth.
Increased heart rate and palpitations can also occur with methylphenidate.
Some patients experience excessive sweating and ulceration of the digits.
Less frequently, patients may develop blurred vision and decreased libido.
Many of these adverse effects can be minimized by dose adjustments and by avoiding an afternoon or evening dose, as advised by a healthcare professional.
Methylphenidate inhibits the metabolism of warfarin, phenytoin, tricyclic antidepressants, and selective serotonin re uptake inhibitors and increases their concentrations.
Therefore, caution should be taken when taking these medications and methylphenidate concurrently.
Methylphenidate should not be given to any patient who has hypersensitivity to it.
Other contraindications include the following.
Glaucoma.
Severe hypertension.
Motor tics.
Personal or family history of Tourette syndrome.
Age less than 6 years.
Structural cardiac abnormalities, cardiomyopathy, and arrhythmias.
In addition, patients should not be given methylphenidate if they are taking monoamine oxidase inhibitors.
There should be a minimum of at least 14 days after discontinuation of monoamine oxidase inhibitors before methylphenidate is given due to the risk of hypertensive crisis.

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