This section describes a group of major adverse reactions associated with use of psychiatric medications. Minor adverse reactions and side effects are outlined on the pages of the respective medications. Although the adverse drug reactions discussed below (with the exception of serotonin syndrome) are most commonly produced by antipsychotic medications, they may occur in response to other medications. The major adverse drug reactions to antipsychotics, their risk factors, onset, and treatment are outlined in Table 16-1. Although the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, classifies dystonia, akathisia, extrapyramidal symptoms (EPS), neuroleptic malignant syndrome (NMS), and tardive dyskinesia as neuroleptic-induced movement disorders, it is clear that akathisia can occur with the use of nonneuroleptic psychiatric medications.

Dystonia

Dystonia is a neuroleptic-induced movement disorder characterized by muscle spasms. Dystonia commonly involves the musculature of the head and neck but may also include the extremities and trunk.

Symptoms may range from a mild subjective sensation of increased muscle tension to a life-threatening syndrome of severe muscle tetany and laryngeal dystonia (laryngospasm) with airway compromise.

The muscle spasms may lead to abnormal posturing of the head and neck with jaw muscle spasm. Spasm of the tongue leads to macroglossia and dysarthria; pharyngeal dystonia may produce impaired swallowing and drooling. Ocular muscle dystonia may produce oculogyric crisis.

Risk factors include use of high-potency antipsychotics; young men are at increased risk. The condition usually develops early in drug therapy (within days).

Treatment of dystonia depends on the severity of the symptoms. In the absence of laryngospasm or severe patient discomfort, intramuscular (1M) anticholinergic medication (benztropine or diphenhydramine) can be used. In more severe cases or if laryngospasm is present, IV anticholinergic medication is used. Some cases may require intubation if respiratory distress is severe. Discontinuation of the precipitating antipsychotic is sometimes necessary; in other cases, the addition of anticholinergic medications on a standing basis prevents the recurrence of dystonia.

Akathisia

Akathisia, a common side effect produced by antipsychotic medications, is also caused by serotonin reuptake inhibitors. Akathisia consists of a subjective sensation of inner restlessness or a strong desire to move one’s body. Individuals with akathisia may appear anxious or agitated. They may pace or move about, unable to sit still. Akathisia can produce severe dysphoria and anxiety in patients and may drive them to become assaultive or to attempt suicide. It is important to accurately diagnose akathisia because if mistaken for agitation or worsening psychosis, antipsychotic dosage may be increased with resultant worsening of the akathisia.

Risk factors for akathisia include a recent increase in medication dosing or the recent onset of medication use. Most cases occur within the first month of drug therapy but can occur anytime during treatment.

Treatment consists of reducing the medication (if possible) or using either beta blockers (propanolol is commonly used) or benzodiazepines (especially lorazepam). Although there is some doubt as to their efficacy, anticholinergics (diphenhydramine or benztropine) are also used frequently.