9-18. ADVERSE EFFECTS ASSOCIATED WITH ANTIPSYCHOTIC AGENTS
As with most drugs, the antipsychotic agents produce some adverse effects.
Discussed below are some of those reactions:
a. Extrapyramidal Reactions. Extrapyramidal reactions are manifested by a
parkinson-like syndrome. That is, the patient has tremors, muscular rigidity, postural
abnormalities, pill-rolling movements with the fingers, and hypersalivation. Fortunately,
these symptoms may be relieved or lessened, or the reactions may be prevented before
they occur by the administration of diphenhydramine (Benadryl).
b. Drowsiness, Dizziness, and Fatigue. Although a sedative-effect is
produced by many of the antipsychotic agents, this effect is short-lived because
tolerance develops after one to three days.
c. Orthostatic Hypotension. Orthostatic hypotension (low blood pressure) is
an adverse reaction produced by some of the antipsychotic agents. Patients
experiencing this problem are at risk of fainting and injuring themselves.
9-19. DOSAGE PRINCIPLE ASSOCIATED WITH THE ANTIPSYCHOTIC AGENTS
You should be familiar with a dosage principle associated with the antipsychotic
agents. This principle is: "High dosage-low potency/low dosage-high potency."
a. High Dosage/Low Potency. Initially when treating a psychotic patient, a
psychiatrist might choose to select a drug that can be given in a high dosage (large
amount of drug) because of its low potency. This allows the psychiatrist some freedom
in dosage-especially if the patient is uncontrollable--without potential harm to the
patient. High dosage/low potency drugs usually have a high incidence of anticholinergic
side effects, but low incidence of extrapyramidal side effects.
b. Low Dosage/High Potency. After a patient has been on one antipsychotic
agent and has been stabilized, the psychiatrist may choose to use another agent that
can be given in smaller amounts (low dosage) because of its high potency. Usually,
more potent drugs are easier to administer (that is, in tablet form). Low dosage/high
potency drugs usually have a low incidence of anticholinergic side effects, but high
incidence of extrapyramidal side effects