Drug Interaction Report

Efavirenz may reduce the blood levels of dihydrocodeine, which may make dihydrocodeine less effective in treating your condition. Additionally, if you have been receiving treatment with dihydrocodeine, adding efavirenz may cause you to experience unpleasant withdrawal symptoms such as excessive sweating, chills, flushing, restlessness, irritability, anxiety, tremor, rapid heartbeat and nausea. On the other hand, if you have been receiving both medications, suddenly discontinuing efavirenz may increase the blood levels of dihydrocodeine, which could increase or prolong its adverse 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. 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.

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.