Side effects for any psychoactive drug are difficult to predict, though<unk>  is usually well tolerated. Commonly reported side effects for<unk> , some of which tend to subside with continued use, include: *Dizziness *Respiratory depression (impaired breathing) *Drowsiness *Intoxicated feeling *Light-headedness *Nausea *Sedation *Euphoria *Severe impairment of judgment *Diarrhea *Memory Loss *Constipation Fioricet (50/40/325) Rare side-effects include Stevens–Johnson syndrome, an adverse reaction to barbiturates, and anaphylaxis. The risk and severity of all side effects is greatly increased when<unk>  (or<unk> -containing medications) are combined with other sedatives (ex. ethanol, opiates, benzodiazepines, antihistamines). In particular,<unk> , especially when combined with other sedatives (e.g. opioids), can cause life-threatening respiratory depression and death. Inhibitors of the hepatic enzyme CYP3A4 may also increase the risk, severity, and duration of side effects, many drugs inhibit this enzyme as do some foods such as grapefruit and the blood orange. Taking<unk> -based medications with some other drugs may also increase the side effects of the other medication.
Butalbital
Ephedrine
Theobromine
Butabarbital
Pseudoephedrine
Bethanechol
Clopenthixol
Guaifenesin