Dosage must be individualized and adjusted according to the severity of the condition and the response obtained. As with all potent drugs, the best dose is the lowest dose that will produce the desired clinical effect. Since extrapyramidal symptoms increase in frequency and severity with increased dosage, it is important to employ the lowest effective dose. These symptoms have disappeared upon reduction of dosage, withdrawal of the drug, or administration of an antiparkinsonian agent.
Prolonged administration of doses exceeding 24 mg daily should be reserved for hospitalized patients or patients under continued observation for early detection and management of adverse reactions. An antiparkinsonian agent, such as trihexyphenidyl hydrochloride or benztropine mesylate, is valuable in controlling drug-induced extrapyramidal symptoms.
Suggested dosages for various conditions follow:
Moderately disturbed nonhospitalized patients with schizophrenia
4 to 8 mg t.i.d. initially; reduce as soon as possible to minimum effective dosage.
Hospitalized patients with schizophrenia
8 to 16 mg b.i.d. to q.i.d.; avoid dosages in excess of 64 mg daily.
Severe nausea and vomiting in adults
8 to 16 mg daily in divided doses; 24 mg occasionally may be necessary, early dosage reduction is desirable.
Elderly Patients
With increasing age, plasma concentrations of perphenazine per daily ingested dose increase. Geriatric dosages of perphenazine preparations have not been established, but initiation of lower dosages is recommended. Optimal clinical effect or benefit may require lower doses for a longer duration. Dosing of perphenazine may occur before bedtime, if required.
