| NALTREXONE HYDROCHLORIDE
Classifications: narcotic (opiate) antagonist; Therapeutic: narcotic antagonist
Prototype: Naloxone HCl
Pregnancy Category: C
25 mg, 50 mg, 100 mg tablets; 380 mg injection
Pure opioid antagonist with prolonged pharmacologic effect, structurally and pharmacologically similar to naloxone. Mechanism
of action not clearly delineated, but it appears that its competitive binding at opioid receptor sites reduces euphoria
and drug craving without supporting the addiction.
Weakens or completely and reversibly blocks the subjective effects (the "high") of IV opioids and analgesics possessing
both agonist and antagonist activity.
Adjunct to the maintenance of an opioid-free state in detoxified addicts who are and desire to remain narcotic free. Management
of alcohol dependence as an adjunct to social and psychotherapeutic methods.
Patients receiving opioid analgesics or in acute opioid withdrawal; opioid-dependent patient; acute hepatitis, liver failure.
Also contraindicated in any individual who (1) fails naloxone challenge, (2) has a positive urine screen for opioids, or
(3) has a history of sensitivity to naltrexone; pregnancy (category C), lactation. Safe use in children <18 y is not established.
Route & Dosage
|Treatment of Opiate Cessation
Adult: PO 25 mg followed by another 25 mg in 1 h if no withdrawal response; maintenance regimen is individualized (max: 800 mg/d)
Adult: PO 50 mg once/d IM 380 mg qmo
Give the naloxone challenge test (administered IV of SC) before starting the abstinence program with naltrexone.
- SC dose: The SC dose is followed by an observation period of 45 min for symptoms of withdrawal (see below).
- IV dose: A portion of the IV dose is injected and, with the needle left in place, the patient is observed for 30 sec for
withdrawal symptoms. If none are observed, remainder of dose is injected and patient is observed for the next 20 min.
- Withdrawal symptoms: Stuffiness or runny nose; tearing; yawning; sweating; tremors; vomiting; gooseflesh; feeling of temperature
change; bone, joint, and muscle pains; abdominal cramps.
- Interpretation: Evidence of withdrawal symptoms indicates that the patient is a potential risk and should not enter a naltrexone
- Do not give naltrexone until patient is opiate free for at least 710 d.
- Give without regard to food.
Adverse Effects (≥1%)GI:
Dry mouth, anorexia, nausea, vomiting, constipation
, abdominal cramps/pain, hepatotoxicity. Musculoskeletal: Muscle and joint pains. CNS: Difficulty sleeping, anxiety, headache, nervousness,
reduced or increased energy, irritability, dizziness, depression
Skin rash. Body as a Whole:
Increased somnolence and lethargy with phenothiazines
; reverses analgesic effects of narcotic
Rapidly from GI tract; 20% reaches systemic circulation (first pass effect). Onset:
1530 min. Peak:
1 h. Duration:
2472 h PO; 4 wk IM. Metabolism:
In liver to active metabolite. Elimination:
In urine. Half-Life:
1013 h PO, 510 d IM.
Assessment & Drug Effects
- Lab tests: Check liver function before the treatment is started, at monthly intervals for 6 mo, and then periodically as
Patient & Family Education
- Note: Naltrexone therapy may put you in danger of overdosing if you use opiates. Small doses even at frequent intervals will give
no desired effects; however, a dose large enough to produce a high is dangerous and may be fatal.
- It may be possible to transfer from methadone to naltrexone. This can be done after gradual withdrawal and final discontinuation
- Report promptly onset of signs of hepatic toxicity (see Appendix F) to physician. The drug will be discontinued.
- Do not self-dose with OTC drugs for treatment of cough, colds, diarrhea, or analgesia. Many available preparations contain
small doses of an opioid. Consult physician for safe drugs if they are needed.
- Tell a doctor or dentist before treatment that you are using naltrexone.
- Wear identification jewelry indicating naltrexone use.