This section includes medications that are commonly used in psychiatric practice but that do not fall into the conventional categories of psychotherapeutic drugs. Many medications used in general medical practice have side effects such as sedation, stimulation, or anxiolysis. Thes side effects are often exploited in psychiatry to target specific symptoms (e.g., insomnia, anergia). Other drugs, such as psychostimulants, have precise indications for psychiatric usage. Many more medications than are discussed here are included in the psychiatric armamentarium.

Psychostimulants

Psychostimulants are used in psychiatry to treat attention deficit disorder, narcolepsy, and some forms of depression (Table 15-1). The most commonly used psychostimulants are dextroamphetamine (Dexedrine), methylphenidate (Ritalin), and pemoline (Cylert).

The mechanism of action of these medications appears to occur through their alterations of central nervous system (CNS) monoamine function. Their primary mechanism of action is thought to be facilitating endogenous neurotransmitter release (rather than acting as a direct agonist).

Psychostimulants have the liabilities of inducing tolerance and psychological dependence, which may lead to abuse. The side effects of these medications are due largely to their sympathomimetic actions and include tachycardia, insomnia, anxiety, hypertension, and diaphoresis. Weight loss may be an unwanted side effect in young children but a desirable one in overweight adults.

Anticholinergics

Medications with anticholinergic activity are commonly used in psychiatry to treat or provide prophylaxis for some types of neuroleptic-induced movement disorders (Table 15-1). Anticholinergics are generally used as first-line agents in the treatment of neuroleptic-induced parkinsonism and for acute dystonia; they may also have some utility in treating akathisia but are best tried after beta blockers and lorazepam. The most commonly used anticholinergics are benztropine and trihexyphenidyl. In addition, diphenhydramine, an antihistamine that also possesses anticholinergic properties, is frequently used to treat neuroleptic-induced movement disorders and to provide nonspecific sedation. These medications are CNS muscarinic antagonists.

Side effects of anticholinergics, due to peripheral anticholinergic action, include blurry vision (due to cycloplegia), constipation, and urinary retention; their principal central side effects are sedation and delirium. Anticholinergic toxicity is a major cause of delirium, especially in individuals with dementia and HIV encephalopathy.

Beta Blockers

Beta blockers are used widely in general medicine. In psychiatry, they have a few specific indications (see Table 15-1). Beta blockers likely alter behavior and mood states by altering both central and peripheral catecholamine function. For example, in anxiety, they may diminish central arousal; peripherally, they may reduce tachycardia, tremor, sweating, and hyperventilation. Common side effects of beta blockers include bradycardia, hypotension, asthma exacerbtion, and masked hypoglycemia in diabetics. Beta blockers may also produce depression-like syndromes characterized by fatigue and depressed mood.

Disulfiram (Antabuse)

Disulfiram is used to prevent alcohol ingestion through the fear of the consequences of ingesting alcohol while taking disulfiram (Table 15-1). Disulfiram blocks the oxidation of acetaldehyde, a step in the metabolism of alcohol. The buildup of acetaldehyde produces a toxic reaction, making an individual who ingests alcohol while taking disulfiram severely ill within 5 to 10 minutes. Symptoms include flushing, headache, sweating, dry mouth, nausea, vomiting, and dizziness. In more severe reactions, chest pain, dyspnea, hypotension, and confusion occur.

Fatal reactions, although rare, can occur. Disulfiram use should be restricted to carefully selected patients who are highly motivated and who fully understand the consequences of drinking alcohol while taking disulfiram. Side effects in the absence of alcohol ingestion include hepatitis, optic neuritis, and impotence.

Clonidine

Clonidine is a CNS alpha₂ adrenoreceptor agonist.

The alpha ₂ adrenoreceptor is a presynaptic autoreceptor that inhibits the release of CNS norepinephrine. Clonidine’s primary use in medicine is as an antihypertensive (Table 15-1). In psychiatry, clonidine has been variously used. It is effective in decreasing autonomic symptoms associated with opiate withdrawal and in the treatment of Tourette’s syndrome, and may be useful for impulsiveness and other forms of behavioral dyscontrol. Side effects include sedation, dizziness, and hypotension.

Cognitive Enhancers

Donepezil (Aricept) and tacrine (Cognex) are reversible inhibitors of the enzyme acetylcholinesterase and are used to enhance cognition in patients with mild to moderate dementia of the Alzheimer’s type. Some of the cognitive deficits in Alzheimer’s disease are due to loss of cholinergic neurons in the basal forebrain that project to the cerebral cortex and hippocampus, which results in a deficiency of cholinergic neurotransmission.

By inhibiting the enzyme that hydrolyzes synaptic acetylcholine, these drugs are thought to raise synaptic concentrations of acetylcholine in the remaining cholinergic neurons. Initially, these drugs reduce cognitive impairment; however, this effect wanes with the progressive loss of cholinergic neurons. Common side effects include gastrointestinal upset and other cholinomimetic effects including bradycardia and increased gastric acid secretion. Tacrine can cause elevations in serum transaminases.

Thyroid Hormones

Thyroid hormones are used primarily in psychiatry to augment the effects of antidepressants (Table 15- 1). They also may be used as adjuncts in treating rapid cycling bipolar disorder. Although clinical hypothyroidism can mimic the symptoms of depression, some individuals without clinical hypothyroidism may respond to thyroid augmentation.

The theoretic basis for using thyroid hormones lies in the finding of altered hypothalamic-pituitary-adrenal axis functioning in depressed individuals. Although there is debate as to their relative efficacy, both T ₃ (tri-iodo thyronine) and T₄ (tetra-iodo thyronine) cross the blood brain barrier. T₄ has been shown to be of use in conjunction with lithium to improve clinical control of rapid cycling bipolar disorder. Side effects at low doses are minimal; when dosages result in over-replacement, symptoms of hyperthyroidism emerge.