• you are allergic to any ingredient in Desyrel or nefazodone
• you are taking sodium oxybate (GHB).

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Desyrel. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have heart disease including irregular heartbeat or have had a heart attack
• if you have a history of depression or suicidal tendencies
• if you are scheduled to have surgery
• if you consume alcoholic beverages.

Some medicines may interact with Desyrel. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Carbamazepine, ethanol, ginkgo biloba, HIV protease inhibitors (eg, ritonavir), phenothiazines (eg, thioridazine), or serotonin reuptake inhibitors (eg, fluoxetine) because side effects, such as increased drowsiness or blurred vision, may occur
• Buspirone, carbamazepine, digoxin, hydantoins (eg, phenytoin), itraconazole, ketoconazole, nefazodone, serotonin reuptake inhibitors (eg, fluoxetine), or sodium oxybate (GHB) because the risk of their side effects may be increased by Desyrel
• Anticoagulants (eg, warfarin) because they may decrease Desyrel's effectiveness. Your doctor may want to adjust your dose while taking Desyrel.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Desyrel may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Desyrel may cause drowsiness, dizziness, or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Desyrel with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Do not drink alcohol or use medicines that may cause drowsiness (eg, sleep aids, muscle relaxers) while you are using Desyrel; it may add to their effects. Ask your pharmacist if you have questions about which medicines may cause drowsiness.
• Tell your doctor or dentist that you take Desyrel before you receive any medical or dental care, emergency care, or surgery.
• Desyrel should not be used in children younger 6 years; safety and effectiveness in these children have not been confirmed.
• Desyrel may rarely cause a prolonged, painful erection. This could happen even when you are not having sex. If this is not treated right away, it could lead to permanent sexual problems, such as impotence. Contact your doctor right away if this happens.
• Pregnancy and breast-feeding: If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Desyrel while you are pregnant. Desyrel is found in breast milk. If you are or will be breast-feeding while you use Desyrel, check with your doctor. Discuss any possible risks to your baby.

Check with your doctor if any of these most common side effects persist or become bothersome:

Blurred vision; constipation; decreased appetite; dizziness; drowsiness; dry mouth; general body discomfort; headache; incoordination; light-headedness; muscle aches/pains; nausea; nervousness; sleeplessness; stomach pain; stuffy nose; swelling of the skin; tiredness; tremors.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blood in urine; chest pain; fainting; hallucinations; irregular heartbeat; light-headedness when rising from a lying or seated position; prolonged, inappropriate, or painful erections; seizures; shortness of breath; stroke; vomiting.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.