DRONABINOL

DRONABINOL
(droe-nab'i-nol)
Marinol, THC
Classifications: antiemetic; cannabinoid;
Therapeutic: antiemetic; appetite stimulant
Pregnancy Category: C
Controlled Substance: Schedule III

Availability

2.5 mg, 5 mg, 10 mg capsules

Action

Synthetic derivative of tetrahydrocannabinol (THC), the principal psychoactive constituent of marijuana (Cannabis sativa). Mechanism unclear: Inhibits vomiting through the control mechanism in the medulla oblongata, producing potent antiemetic effect. Has complex CNS effect that necessitates close supervision of the patient during drug use. Decreases REM sleep; effect on BP is unpredictable; oral temperature may be decreased, and heart rate may be increased. Risk of drug abuse is high.

Therapeutic Effect

Produces potent antiemetic effect and is used to treat chemotherapy-induced nausea and vomiting.

Uses

To treat chemotherapy-induced nausea and vomiting in cancer patients who fail to respond to conventional antiemetic therapy. Appetite stimulant for AIDS patients.

Unlabeled Uses

Glaucoma.

Contraindications

Nausea and vomiting caused by other than chemotherapeutic agents; hypersensitivity to dronabinol or sesame oil; pregnancy (category C); lactation.

Cautious Use

First exposure, especially in the older adult or cardiac patient; hypertension, cardiovascular disorders; epilepsy; psychiatric illness, patient receiving other psychoactive drugs; severe hepatic dysfunction.

Route & Dosage

Chemotherapy-Induced Nausea
Adult/Child: PO 5 mg/m² 1–3 h before administration of chemotherapy, then q2–4h after chemotherapy for a total of 4–6 doses, dose may be increased by 2.5 mg/m² (max: of 15 mg/m² if necessary)

Appetite Stimulant
Adult: PO 2.5 mg b.i.d., before lunch and dinner

Administration

Oral

Do not repeat dose following a reaction until patient's mental state has returned to normal and the circumstances have been evaluated.
Store at 8°–15° C (46°–59° F).

Adverse Effects (≥1%)

CNS: Drowsiness, psychologic high, dizziness, anxiety, confusion, euphoria, sensory or perceptual difficulties, impaired coordination, depression, irritability, headache, ataxia, memory lapse, paresthesias, paranoia, depersonalization, disorientation, tinnitus, nightmares, speech difficulty, facial flush, diaphoresis. CV: Tachycardia, orthostatic hypotension, hypertension, syncope. GI: Dry mouth, diarrhea, fecal incontinence. Other: Muscular pains.

Interactions

Drug: Alcohol and other cns depressants may exaggerate psychoactive effects of dronabinol; tricyclic antidepressants, atropine may cause tachycardia.

Pharmacokinetics

Absorption: Rapidly absorbed from GI tract, with bioavailability of 10–20%. Peak: 2–3 h. Distribution: Fat soluble; distributed to many organs; distributed into breast milk. Metabolism: In liver; extensive first-pass metabolism. Elimination: Principally in bile; 50% in feces within 72 h; 10–15% in urine. Half-Life: 25–36 h.

Nursing Implications

Assessment & Drug Effects

Monitor patients with hypertension or heart disease for BP and cardiac status.
Response to dronabinol is varied, and previous uneventful use does not guarantee that adverse reactions will not occur. Effects of drug may persist an unpredictably long time (days). Extended use at therapeutic dosage may cause accumulation of toxic amounts of dronabinol and its metabolites.
Watch for disturbing psychiatric symptoms if dose is increased: Altered mental state, loss of coordination, evidence of a psychologic high (easy laughing, elation and heightened awareness), or depression.
Note: Abrupt withdrawal is associated with symptoms (within 12 h) of irritability, insomnia, restlessness. Peak intensity occurs at about 24 h: Hot flashes, diaphoresis, rhinorrhea, watery diarrhea, hiccups, anorexia. Usually, syndrome is over in 96 h.

Patient & Family Education

Do not drive or engage in other potentially hazardous activities that require alertness and judgment because of high incidence of dizziness and drowsiness.
Understand potential (reversible) for drug-induced mood or behavior changes that may occur during dronabinol use.
Do not ingest alcohol during period of systemic dronabinol effect. Effect on blood ethanol levels is complex and unpredictable.

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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