Dosage and Administration
A wide range is covered from 25 mg oral or intramuscular for mild sedation, every 8 hours, up to 100 mg every 6 hours for severely ill patients. Initial doses should be low and be increased gradually. It is recommended that most of the daily dose is given at bedtime for maximum hypnotic activity and minimal daytime sedation and hypotension. In the US there are controlled release forms of chlorpromazine (e.g. 300 mg). After the individual dose is well established, such a CR capsule can be given with the evening meal as a single dose, covering the next 24 hours. It is often administered in acute settings as a syrup, which has a faster onset of action than tablets, and is more difficult to spit out to avoid taking.
Chlorpromazine and other antipsychotic drugs need to be taken long-term to prevent the symptoms of the disease from reappearing. Abuse of antipsychotics is unlikely due to their unpleasant effects, in fact these effects often lead patients to stop taking them. For this reason various administration techniques have been developed that do not depend on a patient's compliance. Among them is administration of depot injections which slowly releases the drug and maintains the appropriate blood levels. The technique involves an IM dose injected into a muscle (usually the gluteus medius) of the buttocks or deltoid muscle in the shoulder. The drug slowly diffuses into the body fluids. A single depot injection of an antipsychotic drug can be effective for as long as four weeks. Chlorpromazine is not available as a depot medication.
Previously, higher doses, up to 1200 mg daily or more, were used in acute psychosis. However, this range has markedly decreased in recent years, and dosing aims for the lowest possible with good therapeutic effect. Dosage in ambulatory patients should be particularly low (minimizing sedation and hypotension). Intravenous injection of undiluted solution is contraindicated due to risk of massive fall in blood pressure, cardiovascular collapse. For intravenous infusion of dilutions, the (hospitalized) patient should be lying and the infusion rate should be as slow as possible. Afterward the patient should rest in the lying position for at least 30 minutes.
All patients treated with chlorpromazine on a long-term-basis should have the following checked regularly: blood-pressure, pulse rate, laboratory-tests (liver function tests, kidney-values, blood cell counts, ECG and EEG. Some side effects seem to appear more frequently during the first months of therapy (sedation, hypotension, liver damage) while others such as tardive dyskinesia can appear over time.
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