Taking fluoxetine with other drugs that make you sleepy or slow your breathing can cause dangerous side effects or death. Ask your doctor before taking a sleeping pill, narcotic pain medicine, prescription cough medicine, a muscle relaxer, or medicine for anxiety, depression, or seizures. One should consult his/her doctor immediately, if any side effects are observed after taking this medicine. Also, one should not suddenly stop taking this medicine, as sudden withdrawal may result in headache, nausea, dizziness, and anxiety. Our Prozac Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication. This is not a complete list of side effects and others may occur. Although not all of these side effects may occur, if they do occur they may need medical attention. Check with your doctor immediately if any of the following side effects occur while taking fluoxetine: Do not take St John's wort, the herbal remedy for depression, while you are being treated with fluoxetine as this will increase your risk of side effects. Important Tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements. Increased side effects: Taking fluoxetine with certain medications raises your risk of side effects. This is because fluoxetine and these other medications can cause the same side effects. These. Side Effects. Drug information provided by: IBM Micromedex. Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Fluoxetine may cause other side effects. Call your doctor if you have any unusual problems while taking this medication. Call your doctor if you have any unusual problems while taking this medication.