Drug-induced parkinsonism

Drug-induced parkinsonism (DIP) is the most common drug-induced movement disorder and is most commonly associated with antipsychotic drugs, monoamine reuptake inhibitors, and calcium channel blockers. DIP manifests as a typical movement disorder, which makes it practically indistinguishable from idiopathic Parkinson's disease (PD) and requires differential diagnosis. DIP symptoms develop fairly quickly (hours to weeks) after the antipsychotic is started or after the dose is increased. Therefore, DIP is predominantly a clinical diagnosis that must be kept in mind when a patient develops typical symptoms during treatment onset or increasing the dose of drugs that most often lead to such an adverse reaction (ADR). DIP evaluation includes using the Naranjo algorithm, which helps assess a causal relationship between drug intake and the development of parkinsonism symptoms. The primary DIP treatment is the reduction of the dose of the inducer drug, or its cancellation, or replacement with another drug. In patients with schizophrenia and antipsychotic-induced DIP, dose reduction, replacement with another medication, or prescription of a drug with anticholinergic activity may be possible. The awareness of the doctor and the patient about the possibility of developing this ADR is crucial in the prevention of DIP. Therefore, choosing a drug with the lowest risk of developing DIP is necessary for pharmacotherapy.

Monoamine Reuptake Inhibitors in Parkinson’s Disease

The motor manifestations of Parkinson’s disease (PD) are secondary to a dopamine deficiency in the striatum. However, the degenerative process in PD is not limited to the dopaminergic system and also affects serotonergic and noradrenergic neurons. Because they can increase monoamine levels throughout the brain, monoamine reuptake inhibitors (MAUIs) represent potential therapeutic agents in PD. However, they are seldom used in clinical practice other than as antidepressants and wake-promoting agents. This review article summarises all of the available literature on use of 50 MAUIs in PD. The compounds are divided according to their relative potency for each of the monoamine transporters. Despite wide discrepancy in the methodology of the studies reviewed, the following conclusions can be drawn: (1) selective serotonin transporter (SERT), selective noradrenaline transporter (NET), and dual SERT/NET inhibitors are effective against PD depression; (2) selective dopamine transporter (DAT) and dual DAT/NET inhibitors exert an anti-Parkinsonian effect when administered as monotherapy but do not enhance the anti-Parkinsonian actions of L-3,4-dihydroxyphenylalanine (L-DOPA); (3) dual DAT/SERT inhibitors might enhance the anti-Parkinsonian actions of L-DOPA without worsening dyskinesia; (4) triple DAT/NET/SERT inhibitors might exert an anti-Parkinsonian action as monotherapy and might enhance the anti-Parkinsonian effects of L-DOPA, though at the expense of worsening dyskinesia.