Naltrexone (Revia) hydrochloride opioid antagonist is a synthetic congener of oxymorphone with no opioid agonist properties. Naltrexone hydrochloride is a white crystalline compound soluble in water and available as scored tablets containing 50mg of naltrexone hydrochloride.
Naltrexone hydrochloride markedly attenuates or completely blocks, reversibly, the subjective effects of IV administered opioids. When co-administered with morphine on a chronic basis, naltrexone hydrochloride blocks the physical dependence to morphine, heroin and other opioids. Administration of naltrexone hydrochloride is not associated with development of tolerance or dependence. Naltrexone hydrochloride competitively binds to the opioid receptors.
The mechanism of action of naltrexone hydrochloride in alcoholism is not understood, but blockage of effect of endogenous opioids showed reduction in alcohol consumption by animals in clinical studies.
Indications for Medication
Naltrexone hydrochloride may be used as an aid in the management of selected recovering narcotic dependent or alcoholic patients who want to remain in a state of enforced sobriety so that supportive and psychotherapeutic treatment may be applied to best advantage.
Recovering narcotic dependent patients benefit from naltrexone hydrochloride therapy because they know the effects of naltrexone hydrochloride remains for several days after having stopped taking it. In this way, a relapse must be "planned" rather than impulsively occurring. If an impulsive "slip" does occur, the presence of naltrexone hydrochloride blocks the effects of exogenously administered opioids, thereby preventing the "high."
Recovering alcoholic patients may benefit from naltrexone hydrochloride therapy through blockade of the effects of opioids endogenously released by alcohol consumption.
The following are some of the contraindications for naltrexone hydrochloride therapy.
- Patients receiving opioid analgesics.
- Patients currently dependent on opioids.
- Patients in acute opioid withdrawal.
- Patients who failed naloxone hydrochloride (Narcan) challenge test or who are positive to urine opioid screens.
- Patients with history of sensitivity to naltrexone hydrochloride.
- Patients with acute hepatitis/liver failure.
To prevent occurrence of acute abstinence syndrome or exacerbation of a preexisting subclinical abstinence syndrome, patients must be opioid-free for 7-10 days before starting naltrexone hydrochloride. Since absence of opioid in the urine is not sufficient proof, Narcan challenge may be done. Patients should be told of the serious consequences of trying to overcome opiate blockade.
Naltrexone hydrochloride is a part of a comprehensive treatment for alcoholism and drug dependence. The patient may want to carry identification to alert medical personnel that the patient is taking naltrexone hydrochloride. If patient requires medical treatment, the patient should be sure to tell the physician about the naltrexone hydrochloride. If the patient attempts to self-administer heroin or other opiate drug in small doses they will not perceive any effect. However, if they take large doses, they may die or sustain serious injury, including coma.
Naltrexone hydrochloride should be considered as only one of the many factors determining the success of treatment of alcoholism. A dose of 50mg once daily is recommended or 100mg every other day.
In treatment for narcotic dependence, naltrexone hydrochloride may be started carefully at an initial dose of 25mg. If no withdrawal symptom occurs, patients may be started on 50mg a day thereafter. But patients should not be treated with naltrexone hydrochloride, if not opioid-free for at least 7-10 days. If there is any doubt, a naloxone hydrochloride (naloxone) challenge test should be done.
Revia may cause liver injury when taken in excess. The patient should be informed that if abdominal pain, white stool, dark urine or yellowing of eyes occurs, they should stop taking it and see the doctor as soon as possible.
In placebo controlled trials, a small fraction of patients who are opioid-free for 7-10 days experienced opioid withdrawal like symptom complex consisting of fearfulness, mild nausea, abdominal cramps, restlessness, bone or joint pain, myalgia and nasal symptoms.
Alcoholism: In an open label study with 570 individuals with alcoholism receiving naltrexone hydrochloride, 2% or more of patients experienced nausea, headache, disorder, nervousness, fatigue, insomnia, vomiting, anxiety, somnolence, depression, suicide ideation and attempt.
Narcotic addiction: The following are the adverse effects reported during clinical trials with narcotic addiction at an incidence of >10% - difficulty sleeping, anxiety, nervousness, abdominal pain/cramps, nausea/vomiting, low energy, joint and muscle pain and headache.
Studies to evaluate possible interaction with other drugs have not been performed. Lethargy and somnolence have been observed following doses of naltrexone hydrochloride and thioridazine. Patients taking naltrexone hydrochloride may not benefit from opioid containing medicines such as cold and cough preparations, anti-diarrhea preparations and opioid analgesics.
The consent form for this medication is "Dual Diagnosis Medications."