Drug Interaction Report

Efavirenz may cause central nervous system side effects such as drowsiness, confusion, hallucinations, abnormal behavior, delusions, and even psychosis-like behavior in some cases. Combining it with other medications that can also affect the nervous system such as clemastine may increase the risk and/or severity of these effects. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid driving, operating machinery, or engaging in potentially hazardous activities requiring mental alertness and motor coordination until you know how the medications affect you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Alcohol can increase the nervous system side effects of clemastine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with clemastine. Do not use more than the recommended dose of clemastine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Taking efavirenz with food increases the amount of medicine in your body, which may increase the frequency of side effects. You should take efavirenz once a day on an empty stomach, preferably at bedtime. Taking it at bedtime may make some side effects such as dizziness, trouble sleeping, drowsiness, trouble concentrating, and/or unusual dreams less bothersome. However, these symptoms may be more severe if efavirenz is used with alcohol or mood-altering (street) drugs. You should avoid driving or operating hazardous machinery until you know how the medication affects you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.