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The pain-relieving effects of any narcotic pain medications you use will be blocked if you use them during your treatment with naltrexone injection. Harmful side effects could also occur.

Before receiving naltrexone injection, tell your doctor if you use any of the following drugs:

• buprenorphine (Buprenex, Subutex);

• butorphanol (Stadol);

• codeine (Tylenol with codeine);

• hydrocodone (Lortab, Vicodin);

• dezocine (Dalgan);

• hydromorphone (Dilaudid);

• levorphanol (Levo-Dromoran);

• meperidine (Demerol);

• methadone (Dolophine, Methadose);

• morphine (Kadian, MS Contin, Roxanol);

• nalbuphine (Nubain);

• nalmefene (Revex);

• naloxone (Narcan);

• oxycodone (OxyContin, Roxicodone, Percocet);

• oxymorphone (Numorphan); or

• propoxyphene (Darvon, Darvocet).

There may be other drugs not listed that can affect naltrexone injection. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• blurred vision or eye problems;

• fast heartbeat;

• mood changes, hallucinations (seeing or hearing things), confusion, thoughts of hurting yourself;

• nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

• ear pain, ringing in your ears;

• feeling light-headed, fainting;

• skin rash or itching; or

• wheezing, difficulty breathing.

Other less serious side effects are more likely to occur, such as:

• feeling anxious, nervous, restless, or irritable;

• increased thirst;

• muscle or joint aches;

• weakness or tiredness;

• sleep problems (insomnia);

• decreased sex drive, impotence, or difficulty having an orgasm; or

• pain, tenderness, itching, or a hard lump where the shot was given.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.