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Most patients taking naltrexone do not experience any significant side effects. When side effects do occur, they often diminish over time as the body adapts to the medication. If any side effects persist or worsen, it is strongly recommended that patients contact a physician.

Common side effects of naltrexone include:

• Mild to moderate abdominal pain or cramping
• Anxiety, restlessness or trouble sleeping (insomnia)
• Headache, joint or muscle pain
• Nausea or vomiting
• Fatigue
• Diarrhea

Less common side effects include:

• Chills or dizziness
• Constipation
• Fast or pounding heartbeat
• Increased thirst
• Loss of appetite
• Sexual problems (in men)
• Irritability
• Cough, sneezing, runny or stuffy nose, hoarseness, sore throat or other sinus problems

More serious side effects are rare, but may occur. Patients are urged to seek medical attention if they experience any of the following:

• Fever
• Skin rash
• Severe abdominal pain
• Blurred vision or eye pain
• Chest pain
• Difficult or frequent urination
• Hallucinations
• Itching
• Ringing in the ears
• Shortness of breath
• Swelling of the face, feet or legs
• Unexplained weight gain
• Confusion, depression or other mood or mental changes