naltrexone (oral)

Contraindicated in:

Hypersensitivity;
Concurrent use of opioid analgesics or physiologic opioid dependence;
Acute opioid withdrawal;
Positive urine screen for opioids;
Failure of a naloxone challenge test.

Use Cautiously in:

History of depression or suicidal behavior/attempt;
Moderate or severe renal impairment;
History of hepatic impairment;
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

CV: palpitations

Derm: rash

EENT: hoarseness, runny/stuffy nose, sinus problems, sneezing

F and E: ↑thirst

GI: abdominal cramps/pain, nausea, ↓appetite, constipation, diarrhea, HEPATOTOXICITY, vomiting

GU: delayed ejaculation, erectile dysfunction

Hemat: eosinophilia, thrombocytopenia

Local: injection site reactions

MS: joint pain, muscle pain

Neuro: anxiety, fatigue, headache, insomnia, nervousness, ↑energy, depression, dizziness, sedation, SUICIDAL THOUGHTS/BEHAVIOR

Resp: EOSINOPHILIC PNEUMONIA(INJECTION), cough

Misc: chills

Interactions ⬆ ⬇

Drug-drug:

Thioridazine may ↑ risk of CNS depression.
May prevent therapeutic effects of opioid analgesics, antidiarrheals, and antitussives.

Availability ⬆ ⬇

(Generic available)

Tablets: 50 mg
Suspension for injection: 380 mg/vial

Route/Dosage ⬆ ⬇

Opioid Dependence

PO (Adults ): Following a negative naloxone challenge and 7–10 days of opioid abstinence (longer for methadone), initial dose is 25 mg. If opioid withdrawal does not occur within 1 hr, additional 25 may be given. Maintenance dose is 50 mg once daily or 50 mg once daily on weekdays and 100 mg on Saturday or 100 mg every other day or 150 mg every 3rd day or 100 mg on Monday and Wednesday and 150 mg on Friday.
IM (Adults ): 380 mg every 4 wk or once monthly.

Alcohol Dependence

PO (Adults ): 50 mg once daily or 50 mg once daily on weekdays and 100 mg on Saturday or 100 mg every other day or 150 mg every third day or 100 mg on Monday and Wednesday and 150 mg on Friday.
IM (Adults ): 380 mg every 4 wk or once monthly.

US Brand Names ⬆ ⬇

naltrexone (injection): Vivitrol

Action ⬆ ⬇

Competitively blocks the effects of opioids, including CNS and respiratory depression, without producing any agonist (opioid-like) effects.
Mechanism in managing alcohol dependence may involve the endogenous opioid system.

Therapeutic effects:

Blocks the effects of opioids in previously dependent patients.
Reduced alcohol-dependent behavior.

Classifications ⬆ ⬇

Therapeutic Classification: alcohol abuse therapy adjuncts

Pharmacologic Classification: opioid antagonists

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed orally, but undergoes extensive first-pass hepatic metabolism, resulting in 5–40% bioavailability. Well absorbed following IM administration.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Extensively metabolized by the liver. Major metabolite (6-beta-naltrexol) has opioid antagonist activity. Metabolites are excreted in urine.

Half-Life: Oral: Naltrexone: 4 hr; 6-beta-naltrexol: 13 hr; IM: Naltrexone: 5–10 days; 6-beta-naltrexol: 5–10 days.

Canadian Brand Names ⬆ ⬇

naltrexone (oral): ReVia

Time/Action Profile ⬆ ⬇

(opioid blockade)

ROUTE	ONSET	PEAK	DURATION
50 mg PO	5 min–1 hr‡	unknown	24 hr‡
100 mg PO	5 min–1 hr‡	unknown	48 hr‡
150 mg PO	5 min–1 hr‡	unknown	72 hr‡
IM	unknown	unknown	4 wk

‡Determined by blockade of effects of 25 mg heroin IV.

Patient/Family Teaching ⬆ ⬇

Explain the purpose and side effects of naltrexone. Instruct patient to take as directed. Do not stop receiving naltrexone without consulting health care provider. Inform patients that there are potentially serious consequences and possibly death if they try to overcome the effects of naltrexone with higher doses of opioids. Do not share medication with others, even if they have similar symptoms; may be harmful. Keep out of children's reach. Advise patient to read Patient Information before starting and with each Rx refill in case of changes.
May cause injection site reactions (cellulitis, induration, hematoma, abscess, sterile abscess, necrosis). Advise patient to monitor injection site and notify health care provider if pain, swelling, tenderness, induration, bruising, pruritus, or redness at the injection site occurs and does not improve or worsens within 2 wk. Promptly refer patients with worsening injection site reactions to a surgeon.
May cause dizziness. Advise patient to avoid driving and other activities requiring alertness until effects of the medication are known.
Encourage patient and family to be alert for emergence of anxiety, agitation, panic attacks, insomnia, irritability, hostility, impulsivity, akathisia, hypomania, mania, worsening of depression, and suicidal ideation, especially during early antidepressant therapy. Assess symptoms on a day-to-day basis as changes may be abrupt. If these symptoms occur, notify health care provider.
Advise patient to immediately report signs and symptoms of hepatotoxicity (fatigue, nausea, upper abdominal pain, yellowing of skin or eyes, dark urine, light-colored stools); naltrexone should be discontinued.
Advise patient and family that patient may be more sensitive to lower doses of opioids after naltrexone treatment stops, when next dose is due, and if a dose is missed. Advise patients that they will not perceive any effects of small doses of opioids and may not experience the same effects from opioid-containing analgesics, antidiarrheals, or antitussives. May lead to overdose, including serious injury, coma, or death.
Educate patients and caregivers on how to recognize respiratory depression and emphasize the importance of calling 911 or getting emergency medical help right away in the event of a known or suspected overdose. Inform patients and caregivers about various ways to obtain naloxone as permitted by individual state naloxone dispensing and prescribing requirements or guidelines (by prescription, directly from a pharmacist, or as part of a community-based program).
Advise patient to notify health care provider of medication regimen prior to treatment or surgery. Medical ID describing medication regimen should be carried in case of emergencies.
Advise patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care provider before taking other medications.
Rep: Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding.

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Indications ⬇

Contraind./Precautions ⬆ ⬇