ABSTRACT
This chapter presents a trade name, classification, approved indications for psychological disorders, available dosage forms, storage, and compatibility, usual dosage and administration, relative contraindications, and clinically significant drug interaction of Phenothiazines. The exact mechanism of action of the phenothiazines is complex and has not yet been fully determined. Their antipsychotic activity appears to be primarily related to an interaction with dopamine-containing neurons, specifically the blockade of dopamine receptors both pre- and post-synaptically. The phenothiazines generally are erratically and poorly absorbed following oral ingestion but are well absorbed following intramuscular injection. Concurrent alcohol use may increase the CNS depressant action of the phenothiazines. Advise patients to avoid, or limit, their use of alcohol while receiving phenothiazine pharmacotherapy. Phenothiazines can antagonize the antihypertensive action of guanethidine by competitively inhibiting its uptake and that of norepinephrine into the adrenergic neuron.
