Buy Fioricet 40mg effects are enhanced by caffeine. Barbiturates, or acetaminophen, caffeine, and butalbital, are a class of drugs. It works by slowing down the brain's nerve impulses that cause pain in migraines and cluster headaches. The combination medication Fioricet 40 mg tablets are used to treat tension headaches. consists of caffeine, butalbital, and paracetamol. It has been demonstrated that this medication helps alleviate headache pain while also promoting drowsiness and relaxation.