Phenothiazines
PREGNANCY CATEGORY C
Therapeutic Actions
Mechanism of action of phenothiazines is not fully understood. Antipsychotic drugs block postsynaptic dopamine receptors in the brain, but this may not be necessary and sufficient for antipsychotic activity; depresses the RAS, including the parts of the brain involved with wakefulness and emesis; anticholinergic, antihistaminic (H1), and alpha-adrenergic blocking activity also may contribute to some of its therapeutic (and adverse) actions.
Indications
Management of manifestations of psychotic disorders
Control of severe nausea and vomiting, intractable hiccups
Contraindications and Cautions
Contraindicated with coma or severe CNS depression, bone marrow depression, blood dyscrasia, circulatory collapse, subcortical brain damage, Parkinson’s disease, liver damage, cerebral arteriosclerosis, coronary disease, severe hypotension or hypertension, prolonged QTc interval.
Use cautiously with respiratory disorders (“silent pneumonia” may develop); glaucoma, prostatic hypertrophy; epilepsy or history of epilepsy; breast cancer; thyrotoxicosis; peptic ulcer, decreased renal function; myelography within previous 24 hr or scheduled within 48 hr; exposure to heat or phosphorous insecticides; pregnancy; lactation; children younger than 12 yr, especially those with chickenpox, CNS infections (children are especially susceptible to dystonias that may confound the diagnosis of Reye’s syndrome).
Adverse Effects
Autonomic: Dry mouth, salivation, nasal congestion, nausea, vomiting, anorexia, fever, pallor, flushed facies, sweating, constipation, paralytic ileus, urine retention, incontinence, polyuria, enuresis, priapism, ejaculation inhibition, male impotence
CNS: Drowsiness, insomnia, vertigo, headache, weakness, tremor, ataxia, slurring, cerebral edema, seizures, exacerbation of psychotic symptoms, extrapyramidal syndromes—pseudoparkinsonism; dystonias; akathisia, tardive dyskinesias, potentially irreversible (no known treatment) neuroleptic malignant syndrome
CV: Hypotension, orthostatic hypotension, hypertension, tachycardia, bradycardia, cardiac arrest, heart failure, cardiomegaly, refractory arrhythmias, pulmonary edema, prolonged QTc interval
EENT: Glaucoma, photophobia, blurred vision, miosis, mydriasis, deposits in the cornea and lens (opacities), pigmentary retinopathy
Endocrine: Lactation, breast engorgement in females, galactorrhea; syndrome of inappropriate ADH secretion; amenorrhea, menstrual irregularities; gynecomastia in males; changes in libido; hyperglycemia or hypoglycemia; glycosuria; hyponatremia; pituitary tumor with hyperprolactinemia; inhibition of ovulation, infertility, pseudopregnancy; reduced urinary levels of gonadotropins, estrogens, progestins
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