These interactions can occur for a number of reasons. In some cases, antifungals interfere with the actions of psychiatric medications. In other cases, they produce unwanted side effects such as drowsiness, dizziness, and rapid heartbeat. They can also affect how psychiatric medications are metabolized, which can impact how long it takes a substance to clear from the body. If a person takes more medication before their last dose has metabolized, it may increase the risk of overdose.