PK-Merz (Amantadine)

Amantadine group – this is the only group of antiparkinsonian drugs that can reduce the manifestations of motor complications from long-term levodopa therapy in the form of choreiform dyskinesias. Most often, they are involuntary, dancing  chaotic movements in the limbs, swaying and jerking movements in the torso, and most often occur at the peak dose of levodopa)

Amantadine has two representatives. PK-Merz (manufacturer – international company Merz), Midantan (produced in Belarus, this medication is included in the drug benefit for patients)

They have different chemical structures: PK-Merz is amantadine sulfate, and midantan is amantadine chloride. This affects differences in the duration of the effect (PK-Merz lasts slightly longer) and the rate of development of drug resistance (midantan is slightly faster).

Amantadines are effective due to several different mechanisms of action.

First, due to the blockade of specific glutamate NMDA-receptors. Glutamate is the main excitatory (and damaging) neurotransmitter, and when there is an excessive accumulation of sodium glutamate, neuron death occurs due to excitotoxicity. This provides an antidyskinetic effect and even possible neuroprotective action (convincing data is not yet available)

Secondly, due to the increased synthesis of dopamine and the decreased reuptake of it, which also increases its quantity. Therefore, the main antiparkinsonian effect manifests as a reduction in all three main symptoms of parkinsonism (hypokinesia/slowness, muscle rigidity/stiffness, resting tremor)

Thirdly, due to the mild anticholinergic effect resulting from decreased acetylcholine production. This may provide additional reduction of resting tremor.

Fourth, PC-Merz is the only antiparkinsonian drug available in infusion form (it can be administered intravenously via drip).

Therefore, the main indications for the use of PC-Merz are:

– early stages of PD (a rather small effect)

– advanced stages of Parkinson’s disease with the development of motor complications in the form of drug-induced dyskinesias

– atypical parkinsonism (together with levodopa medications)

– acute situations (akinetic crisis caused by withdrawal of antiparkinsonian drugs or introduction of neuroleptics, decompensation of PD)

The most common side effects may include skin discoloration in the form of white-blue star-shaped marbling (livedo reticularis) and a decrease in blood pressure. Taking the medication in the evening may cause difficulty falling asleep (therefore, PK-Merz is recommended to be taken in the morning and daytime, strictly before 16:00-18:00). The anticholinergic effect may also cause some confusion and visual hallucinations, exacerbate urinary retention symptoms in the presence of prostate adenoma, arrhythmia, and dry mouth.

Contraindications include renal and hepatic failure, epilepsy, thyrotoxicosis, closed-angle glaucoma, and prostate adenoma. The possibility of developing psychosis and hallucinations is assessed separately (based on existing hallucinations and age).

When prescribing amantadines, as with all other medications, a doctor’s consultation is necessary.

Bless you!