quetiapine fumarate

quetiapine fumarate

(kwe tie' ah peen)

Seroquel

Pregnancy Category C

Drug classes

Dibenzothiazepine

Antipsychotic

Therapeutic actions

Mechanism of action not fully understood: Blocks dopamine and serotonin receptors in the brain; also acts as a receptor antagonist at histamine and adrenergic receptor sites (which may contribute to the adverse effects of orthostatic hypotension and somnolence).

Indications

·        Treatment of schizophrenia in patients > 18 yr

·        Short-term treatment of acute manic episodes associated with bipolar I disorder, as monotherapy or in combination with lithium or divalproex

Contraindications and cautions

·        Contraindicated with coma or severe CNS depression, allergy to quetiapine, lactation.

·        Use cautiously with CV disease, hypotension, hepatic dysfunction, seizures, exposure to extreme heat, autonomic instability, tardive dyskinesia, dehydration, thyroid disease, pregnancy.

Available forms

Tablets—25, 100, 200, 300 mg

Dosages

ADULTS

·        Schizophrenia: 25 mg PO bid. Increase in increments of 25–50 mg bid–tid on days 2 and 3; dosage range by day 4: 300–400 mg/day in two to three divided doses. Further increases can be made at 2-day intervals. Maximum dose, 800 mg/day.

·        Manic episodes: 100 mg/day PO divided bid on day 1; increase to 400 mg/day PO in bid divided doses by day 4 using 100-mg/day increments. Range, 400–800 mg/day given in divided doses.

PEDIATRIC PATIENTS

Not recommended for patients < 18 yr old.

GERIATRIC OR DEBILITATED PATIENTS OR PATIENTS WITH HEPATIC IMPAIRMENT

Use lower doses starting with 25 mg/day and increase dosage more gradually than in other patients.

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	Slow	1.5 hr	Unknown

Metabolism: Hepatic; T_1/2: 6 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Feces, urine

Adverse effects

·        Autonomic: Dry mouth, salivation, nasal congestion, nausea, vomiting, anorexia, fever, pallor, flushed facies, sweating, constipation

·        CNS: Drowsiness, insomnia, vertigo, headache, weakness, tremor, tardive dyskinesias, neuroleptic malignant syndrome

·        CV: Hypotension, orthostatic hypotension, syncope

·        Hematologic: Increased ALT, total cholesterol and triglycerides

·        Other: Risk of development of diabetes mellitus

Interactions

Drug-drug

·        CNS effects potentiated by alcohol, CNS depressants

·        Effects decreased with phenytoin, thioridazine, carbamazepine, phenobarbital, rifampin, glucocorticoids; monitor patient closely and adjust dosages appropriately when these drugs are added to or discontinued from regimen

·        Increased effects of antihypertensives, lorazepam

·        Decreased effects of levodopa, dopamine antagonists

·        Potential for heatstroke and intolerance with drugs that affect temperature regulation (anticholinergics); use extreme caution and monitor patient closely

Nursing considerations

Assessment

·        History: Coma or severe CNS depression; allergy to quetiapine, lactation, pregnancy, CV disease, hypotension, hepatic dysfunction, seizures, exposure to extreme heat, autonomic instability, tardive dyskinesia, dehydration, thyroid disease, suicidal tendencies

·        Physical: Body weight, T; reflexes, orientation, IOP; P, BP, orthostatic BP; R, adventitious sounds; CBC, urinalysis, LFTs, renal and thyroid function tests

Interventions

·        WARNING: Administer small quantity to any patient with suicidal ideation.

·        Monitor elderly patients for dehydration and institute remedial measures promptly; sedation and decreased sensation of thirst related to CNS effects of drug can lead to severe dehydration.

·        Monitor patient closely in any setting that would promote overheating.

·        Regularly monitor patient for signs and symptoms of diabetes mellitus.

·        Consult physician about dosage reduction and use of anticholinergic antiparkinsonians (controversial) if extrapyramidal effects occur.

Teaching points

·        Take this drug exactly as prescribed.

·        This drug should not be used during pregnancy; using barrier contraceptives is advised.

·        Maintain fluid intake and use precautions against heat stroke in hot weather.

·        You may experience these side effects: Dizziness, drowsiness, fainting (avoid driving or engaging in other dangerous activities); dry mouth, nausea, loss of appetite (frequent mouth care, frequent small meals, and increased fluid intake may help).

·        Report sore throat, fever, unusual bleeding or bruising, rash, weakness, tremors, dark-colored urine, pale stools, yellowing of the skin or eyes, suicidal thoughts.

Adverse effects in Italic are most common; those in Bold are life-threatening.