>10%:

Cardiovascular: Hypotension, orthostatic hypotension

Central nervous system: Pseudoparkinsonism, akathisia, dystonias, tardive dyskinesia, dizziness

Gastrointestinal: Constipation

Ocular: Pigmentary retinopathy

Respiratory: Nasal congestion

Miscellaneous: Diaphoresis (decreased)

1% to 10%:

Dermatologic: Increased sensitivity to sun, rash

Endocrine & metabolic: Changes in menstrual cycle, breast pain, libido (changes in)

Gastrointestinal: Weight gain, nausea, vomiting, stomach pain

Genitourinary: Difficulty in urination, ejaculatory disturbances

Neuromuscular & skeletal: Trembling fingers

<1%: Agranulocytosis, cholestatic jaundice, cornea and lens changes, discoloration of skin (blue-gray), galactorrhea, hepatotoxicity, impairment of temperature regulation, leukopenia, lowering of seizure threshold, neuroleptic malignant syndrome (NMS), pigmentary retinopathy, priapism

Aluminum salts: May decrease the absorption of phenothiazines; monitor

Amphetamines: Efficacy may be diminished by antipsychotics. In addition, amphetamines may increase psychotic symptoms; avoid concurrent use.

Anticholinergics: May inhibit the therapeutic response to phenothiazines and excess anticholinergic effects may occur; includes benztropine, trihexyphenidyl, biperiden, and drugs with significant anticholinergic activity (TCAs, antihistamines, disopyramide)

Antihypertensives: Concurrent use of phenothiazines with an antihypertensive may produce additive hypotensive effects (particularly orthostasis)

Bromocriptine: Phenothiazines inhibit the ability of bromocriptine to lower serum prolactin concentrations

CNS depressants: Sedative effects may be additive with phenothiazines; monitor for increased effect; includes barbiturates, benzodiazepines, narcotic analgesics, ethanol, and other sedative agents

Epinephrine: Chlorpromazine (and possibly other low potency antipsychotics) may diminish the pressor effects of epinephrine

Guanethidine and guanadrel: Antihypertensive effects may be inhibited by chlorpromazine

Levodopa: Chlorpromazine may inhibit the antiparkinsonian effect of levodopa; avoid this combination

Lithium: Chlorpromazine may produce neurotoxicity with lithium; this is a rare effect

Metoclopramide: May increase extrapyramidal symptoms (EPS) or risk.

Phenytoin: May reduce serum levels of phenothiazines; phenothiazines may increase phenytoin serum levels

Propranolol: Serum concentrations of phenothiazines may be increased; propranolol also increases phenothiazine concentrations

Polypeptide antibiotics: Rare cases of respiratory paralysis have been reported with concurrent use of phenothiazines

QTc-prolonging agents: Effects on QTc interval may be additive with phenothiazines, increasing the risk of malignant arrhythmias; includes type Ia antiarrhythmics, TCAs, and some quinolone antibiotics (sparfloxacin, moxifloxacin and gatifloxacin)

Sulfadoxine-pyrimethamine: May increase phenothiazine concentrations

Tricyclic antidepressants: Concurrent use may produce increased toxicity or altered therapeutic response

Trazodone: Phenothiazines and trazodone may produce additive hypotensive effects

Valproic acid: Serum levels may be increased by phenothiazines

Onset of action: 2-4 hours

Duration: ~24 hours

Absorption: Tissue saturation, particularly in high lipid tissues (eg, CNS)

Half-life elimination: 20-40 hours

Hospitalized schizophrenic patients may require doses as high as 400-600 mg/day

Hemodialysis: Not dialyzable (0% to 5%)

Peabody CA, Warner MD, Whiteford HA, et al, "Neuroleptics and the Elderly,"J Am Geriatr Soc, 1987, 35(3):233-8.

Risse SC and Barnes R, "Pharmacologic Treatment of Agitation Associated With Dementia,"J Am Geriatr Soc, 1986, 34(5):368-76.

Saltz BL, Woerner MG, Kane JM, et al, "Prospective Study of Tardive Dyskinesia Incidence in the Elderly,"JAMA, 1991, 266(17):2402-6.

Seifert RD, "Therapeutic Drug Monitoring: Psychotropic Drugs,"J Pharm Pract, 1984, 6:403-16.