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Pharmacologic class: Butyrophenone
Therapeutic class: General anesthetic, antiemetic
Pregnancy risk category C
FDA Box Warning
• QT prolongation and torsades de pointes may occur at or below recommended doses, even in patients with no known risk factors. (Risk factors for prolonged QT syndrome include heart failure, bradycardia, cardiac hypertrophy, hypokalemia, hypomagnesemia, age older than 65, alcohol abuse, and use of diuretics, drugs that prolong the QT interval, benzodiazepines, volatile anesthetics, or I.V. opioids.) Some cases have been fatal. Reserve drug for patients with refractory disease. Use with extreme caution in patients at risk for prolonged QT interval.
• Drug is contraindicated in patients with known or suspected QT prolongation.
Produces marked sedation by directly blocking subcortical receptors. Produces antiemetic effect by blocking CNS receptors in chemoreceptor trigger zone.
Injection: 2.5 mg/ml in 1-ml, 2-ml, and 5-ml ampules and in 2-ml, 5-ml, and 10-ml vials
Indications and dosages
➣ Perioperative nausea and vomiting
Adults: Initially, 2.5 mg I.M. or I.V. Additional doses of 1.25 mg may be given. Dosages are highly individualized according to patient's age, weight, physical status, and underlying pathologic condition.
Children ages 2 to 12: Initially, 0.1 mg/kg I.M. or I.V. Additional doses up to a total of 2.5 mg may be given. Dosages are highly individualized according to patient's age, weight, physical status, and underlying clinical condition.
• Elderly or debilitated patients
• High-risk patients (such as patients over age 65 and those with heart failure, alcohol abuse, or other factors that predispose to prolonged QT interval)
• Patients who have received other CNS depressants (such as analgesics or anesthetics)
• Hypersensitivity to drug
• Known or suspected QT-interval prolongation (more than 440 millisec in males or 450 millisec in females)
Use cautiously in:
• severe cardiac or renal disease, diabetes mellitus, respiratory insufficiency, prostatic hypertrophy, angle-closure glaucoma, CNS depression, CNS tumors, intestinal obstruction, bone marrow depression
• elderly patients
• pregnant or breastfeeding patients
• children younger than age 2.
• Know that drug is indicated to ease perioperative nausea and vomiting only in patients who don't respond adequately to other treatment.
• Be aware that drug doesn't need to be diluted for I.V. or I.M. use.
• Give by slow I.V. injection, or inject I.M. into large muscle.
CNS: weakness, dysarthria, dysphonia, dizziness, extrapyramidal reactions, headache, postoperative hallucinatory episodes with transient depression, tremor, irritability, paresthesia, aggression, vertigo, ataxia, loss of consciousness, seizures, neuroleptic malignant syndrome
CV: chest pain, hypertension, hypotension, vasodilation, arrhythmias, atrial fibrillation
EENT: cataracts, blurred vision, eye irritation, sore throat
GI: nausea, vomiting, diarrhea, abdominal cramps, bloating, epigastric pain, fecal incontinence, increased salivation, dysphagia
GU: urinary frequency, increased libido
Hepatic: cholestatic jaundice
Musculoskeletal: muscle cramps, arthritis, bone fractures
Respiratory: bronchitis, dyspnea
Skin: bruising, rash, urticaria, facial sweating, diaphoresis, pruritus, flushing
Other: toothache, weight loss, hot flashes, influenza, chills
Drug-drug. Antihypertensives, nitrates: additive hypertension
CNS depressants (including antidepressants, antihistamines, opioids): additive CNS depression
Drugs that induce hypokalemia or hypomagnesemia (such as diuretics and laxatives and supraphysiologic use of steroid hormones with mineralocorticoid activity): possible precipitation, QT interval prolongation
Drugs that prolong QTc interval (such as antidepressants, class I or III antiarrhythmics, antimalarials, calcium channel blockers, some antihistamines, some neuroleptics): increased risk of conduction abnormalities
Drug-herbs. Chamomile, hops, kava, skullcap, valerian: increased CNS depression
Drug-behaviors. Alcohol use: additive CNS depression
☞ Monitor QT interval; report prolongation. Also watch for torsades de pointes.
☞ Know that drug may cause sudden death at high doses (above 25 mg) in patients at risk for arrhythmias.
☞ Monitor for signs and symptoms of neuroleptic malignant syndrome, such as hyperthermia, severe extrapyramidal symptoms, altered mental status, stupor, coma, hypertension, tachycardia, pallor, or diaphoresis. (However, this syndrome is rare.)
• Assess vital signs frequently. Stay alert for orthostatic hypotension and tachycardia. Keep I.V. fluids and vasopressors on hand to treat pronounced hypotension.
☞ Don't place hypotensive patient in Trendelenburg position because this may deepen anesthesia, precipitating respiratory arrest.
• Avoid abrupt position changes.
• Observe for signs and symptoms of respiratory compromise if drug is used concurrently with narcotics.
• Advise patient not to drink alcohol or take CNS depressants for 24 hours after receiving drug.
• Tell patient drug may cause extreme drowsiness for several days after administration.
• Caution patient not to drive or perform other activities requiring mental alertness.
• Instruct patient to change positions slowly.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, herbs, and behaviors mentioned above.