Naltrexone

INTRODUCTION

Indications

Provides opioid antagonism in the management of opioid dependence (oral only). Management of alcohol dependence.

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.

Adverse Reactions/Side Effects

CV: anxiety, fatigue, headache, insomnia, nervousness, depression, dizziness, increased energy, sedation, suicidal ideation. EENT: hoarseness, runny/stuffy nose, sinus problems, sneezing. Resp: EOSINOPHILIC PNEUMONIA (INJECTION), cough. CV: palpitations. GI: HEPATOTOXICITY, abdominal cramps/pain, nausea, constipation, ↓ appetite, diarrhea, vomiting. GU: delayed ejaculation, erectile dysfunction. Hemat: eosinophilia, thrombocytopenia. Derm: skin rash. Local: injection site reactions. MS: muscle/joint pain. Misc: chills, ↑ thirst.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Monitor any breathing difficulties. Notify physician immediately if patient experiences signs of eosinophilic pneumonia, such as cough, fever, chills, night sweats, and chest pain during inspiration and expiration.

• Be alert for signs of hepatotoxicity, including anorexia, abdominal pain, severe nausea and vomiting, yellow skin or eyes, fever, sore throat, malaise, weakness, facial edema, lethargy, and unusual bleeding or bruising. Notify physician immediately if these signs occur.

• Monitor changes in mood and behavior such as anxiety, nervousness, depression, sedation, suicidal thoughts, or other changes in mental state. Notify physician if these changes become problematic.

• Monitor signs of eosinophilia (fatigue, weakness, myalgia) or thrombocytopenia (bruising, nose bleeds, and bleeding gums). Report these signs to the physician.

• Assess any muscle or joint pain to rule out musculoskeletal pathology; that is, try to determine if pain is drug induced rather than caused by anatomic or biomechanical problems.

• Assess dizziness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

• Monitor IM injection site for pain, swelling, and irritation. Report prolonged or excessive injection site reactions to the physician.

Patient/Client-Related Instruction

• Instruct patient to report bothersome side effects such as severe or prolonged headache, cough, nasal problems, palpitations, erectile dysfunction, skin rash, chills, or GI problems (nausea, vomiting, diarrhea, constipation, abdominal cramps, decreased appetite, increased thirst).

Pharmacokinetics

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

Distribution: Enters breast milk.

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