Motor side-effects

Compared to the older antipsychotics (first-generation antipsychotics), the more recently developed second-generation antipsychotics are associated with a lower risk of motor side effects (tremor, stiffness, restlessness, and dyskinesia) may offer greater benefits for affective, negative, and cognitive symptoms and may prolong the time to psychotic relapse. 

Several different types of serotonin receptor (for example, S-HTi / 5-HT2A/ 5-HT2C/ 5-HTib/id) have been associated with the motor side effects of the SSRIs which may arise should these drugs be administered in conjunction with a monoamine oxidase inhibitor. The 5-HT3 receptor is an example of a non-selective cation charmel receptor which is permeable to both sodium and potassium ions and, because both calcium and magnesium ions can modulate its activity, the 5-HT3 receptor resembles the glutamate-NMDA receptor. Antagonists of the 5-HT3 receptor, such as ondansetron, are effective antiemetics and are particularly useful when... 

When D2 receptors are blocked in the nigrostriatal DA pathway, it produces disorders of movement that can appear very much like those in Parkinson s disease this is why these movements are sometimes called drug-induced parkinsonism (Fig. 11 —4). Since the nigrostriatal pathway is part of the extrapyramidal nervous system, these motor side effects associated with blocking of D2 receptors in this part of the brain are sometimes also called extrapyramidal symptoms, or EPS. 

Several newer antipsychotic medications have been developed that seem different or atypical, compared with their predecessors. These agents include clozapine (Clozaril), risperidone (Risperdal), and several others listed in Tables 8-1 and 8-2. Although there is some debate about what exactly defines these drugs as atypical, the most distinguishing feature is that they have a much better side-effect profile, including a decreased risk of producing extrapyramidal (motor) side effects.17,45,57... 

Motor side effects deserve particular mention. Some can occur as early as a few hours after administration of the first dose (acute dystonia), whereas others (like tardive dyskinesia, a usually irreversible condition) may not appear until after many years of treatment (although... 

By blocking dopamine 2 receptors In the striatum, it can cause motor side effects, especially at high doses... 

Blockade of serotonin type 2A receptors may contribute at clinical doses to cause enhancement of dopamine release in certain brain regions, thus reducing motor side effects and possibly improving cognitive and affective symptoms... 

Partial agonist actions at dopamine 2 receptors in the striatum can cause motor side effects, such as akathisia (occasionally)... 

Benztropine or trihexyphenidyl for motor side effects and akathisia... 

Sometimes amantadine can be helpful for motor side effects... 

Little or no prolactin elevation, motor side effects, or tardive dyskinesia... 

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