AMOXAPINE

AMOXAPINE
(a-mox'a-peen)
Classifications: psychotherapeutic; tricyclic antidepressant;
Therapeutic: antidepressant

Prototype: Imipramine
Pregnancy Category: C

Availability

25 mg, 50 mg, 100 mg, 150 mg tablets

Action

Tricyclic antidepressant (TCA) with mixed antidepressant and tranquilizing properties. Antidepressant activity is thought to be due to reduced reuptake of norepinephrine and serotonin at the cell membrane of the neuron, thus increasing the level of both neurotransmitters.

Therapeutic Effect

Enhancement of neurotransmitters results in its antidepressant activity.

Uses

Neurotic and endogenous depression accompanied by anxiety or agitation.

Contraindications

Hypersensitivity to other tricyclic compounds; acute recovery period after MI; AV block; MAOI therapy, QT prolongation; suicidal ideation; pregnancy (category C), lactation, children <16 y of age.

Cautious Use

History of convulsive disorders, schizophrenia, manic depression, electroshock therapy; alcohol abuse; history of urinary retention, benign prostatic hypertrophy; angle-closure glaucoma or increased intraocular pressure; cardiovascular disorders; impaired renal or hepatic function; elective surgery.

Route & Dosage

Antidepressant
Adult: PO Start at 50 mg b.i.d. or t.i.d., may increase on third day to 100 mg t.i.d. Maintenance doses ≤300 mg/d as single dose at bedtime
Geriatric: PO 25 mg h.s., may increase q3–7d to 50–150 mg/d in divided doses (max: 300 mg/d)

Administration

Oral
  • Give with or after food to reduce GI irritation; tablet may be crushed and taken with fluid or mixed with food.
  • Give maintenance dose as a single dose at bedtime to minimize daytime sedation and other annoying drug adverse effects.
  • Do not abruptly discontinue drug. Doses should be tapered over 2 wk.
  • Store at 15°–30° C (59°–86° F) in tightly closed container unless otherwise directed.

Adverse Effects (≥1%)

CNS: Drowsiness, dizziness, headache, fatigue, sedation, lethargy; extrapyramidal effects (acute dystonic reactions, panic attacks, parkinsonism, tardive dyskinesia), seizures (overdosage). CV: Orthostatic hypotension; arrhythmias. GI: Constipation, diarrhea, flatulence, dry mouth, peculiar taste, nausea, heartburn. Special Senses: Blurred vision, dry eyes. Urogenital: Nephrotoxicity (overdosage).

Interactions

Drug: May decrease response to antihypertensives; cns depressants, alcohol, hypnotics, barbiturates, sedatives potentiate CNS depression; may increase hypoprothrombinemic effect of oral anticoagulants; ethchlorvynol, transient delirium; with levodopa, sympathomimetics (e.g., epinephrine, norepinephrine), possibility of sympathetic hyperactivity with hypertension and hyperpyrexia; with mao inhibitors, possibility of severe reactions: toxic psychosis, cardiovascular instability; methylphenidate increases plasma TCA levels; thyroid drugs may increase possibility of arrhythmias; cimetidine may increase plasma TCA levels. Herbal: Ginkgo may decrease seizure threshold, St. John's wort may cause serotonin syndrome.

Pharmacokinetics

Absorption: Rapidly absorbed. Peak: 1–2 h. Distribution: Probably crosses placenta; distributed into breast milk. Metabolism: Via CYP2D6; active metabolite. Elimination: 60% in urine in 6 d; 7–18% in feces. Half-Life: 8 h parent drug, 30 h metabolite.

Nursing Implications

Assessment & Drug Effects

  • Monitor therapeutic effectiveness. Initial antidepressant effect (mild euphoria, increased energy) may occur within 4–7 d; however, in most patients clinical response does not occur until after 2–3 wk of drug therapy.
  • Supervise patient closely during therapy for suicidal ideation and potential serious adverse effects.
  • Report immediately signs of neuroleptic malignant syndrome: fever, sweating, rigidity (catatonia), unstable BP, rapid, irregular pulse; changes in level of consciousness, coma. Although rare, it can be life-threatening if drug is not stopped immediately. Death can result from acute respiratory, renal, or cardiovascular failure.
  • Report immediately the onset of signs of tardive dyskinesia (see Appendix F); careful observation/reporting may prevent irreversibility.
  • Monitor I&O ratio and bowel elimination pattern. Report continuing constipation.

Patient & Family Education

  • Follow directions for taking this drug (see ADMINISTRATION).
  • Do not abruptly discontinue drug. Dosage should be tapered over 2 wk. Maintain established dosage regimen. Do not skip, reduce, or double doses or change dose intervals.
  • Minimize alcohol intake as it may potentiate drug effects, thus increasing the dangers of overdosage or suicidal ideation.
  • Drink at least 2000 mL (approximately 2 qts) fluid daily and eat foods with high fiber content (if allowed) to provide needed roughage.
  • Monitor weight at least weekly and report significant weight gain.
  • Do not drive or engage in potentially hazardous tasks until response to drug is known.
  • Rinse mouth frequently with clear water, especially after eating, to relieve mouth dryness.
  • Do not take any prescription or OTC drugs without consulting physician.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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