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MDMA, also known as ecstasy, XTC, Adam, and Essence, is a commonly used substance at all-night dance parties known as raves and is also increasingly being used recreationally by young professionals. When MDMA is taken orally as a capsule or tablet at average doses of 75-100 mg,20 users cite enhanced feelings of empathy for others, anxiolysis, and strong feelings of euphoria. MDMA is an amphetamine-like compound that undergoes demethylenation principally by CYP2D6.21-23 Concomitant administration with CYP2D6 inhibitors could lead to significant increases in MDMA exposure with potentially dangerous and even fatal consequences, as illustrated by a case report.18 Within a few hours of taking 180 mg of MDMA, a 32-year-old man with AIDS experienced symptoms suggestive of a heightened serotonergic state including tachypnea, tachycardia, cyanosis, and profuse sweating. He then experienced an apparent tonic-clonic seizure, tachypnea, and tachycardia (carotid pulse 200 beats/min), and subsequently died from cardiorespiratory arrest. This patient had previously taken similar amounts of MDMA on several occasions without adverse effects, but this was the first time he had taken MDMA since adding ritonavir 600 mg twice daily to his antiretroviral regimen. At autopsy, the patient's blood concentrations of MDMA were approximately tenfold higher than expected given the amount ingested. Since ritonavir is a well-known potent inhibitor of many hepatic isoenzymes including CYP2D6, the clinicians concluded that the patient likely experienced a fatal serotonergic reaction to MDMA as a result of an interaction with ritonavir.
The danger associated with this interaction may be magnified due to the large variability in the actual amount of MDMA between tablets and the presence of other chemicals (e.g., amphetamines, ephedrine) in some MDMA tablets whose metabolism can also be inhibited by ritonavir, leading to a life-threatening consequence.24 Thus, the combination of MDMA and ritonavir should be avoided. Other isoforms of the CYP450 system may also be involved in the metabolism of MDMA, notably 1A2, 2B6, and 3A4.23 All PIs can inhibit CYP3A4 activity to varying degrees, and ritonavir, nelfinavir, and the NNRTI efavirenz also demonstrate inhibitory activity against 2B625 ; therefore, individuals using MDMA should be warned about the potential for an interaction with these agents and advised to take appropriate precautions (e.g., use 25% of the usual amount of MDMA, take breaks from dancing, ensure rave or party has medical team on site, maintain adequate hydration by avoiding alcohol and replenishing fluids regularly).
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http://www.natap.org/2003/Jan/010703_3.htm