Which drug is known for a severe hyperthermic syndrome leading to serious complications such as kidney failure?

The drug known for causing severe hyperthermic syndrome, which can lead to serious complications such as kidney failure, is methylenedioxymethamphetamine (MDMA). This substance is commonly associated with recreational use, often referred to as ecstasy, and its effects include increased body temperature, excessive sweating, and dehydration. These physiological changes can result in a dangerous condition known as hyperthermia.

When the body temperature rises significantly, it can affect various organ systems. In particular, it can lead to rhabdomyolysis, a breakdown of muscle tissue that releases myoglobin into the bloodstream, which in turn can cause kidney damage and potentially lead to acute kidney failure.

The other substances listed do not share this specific risk profile. Heroin primarily poses risks of respiratory depression and overdose; flunitrazepam, known for its sedative effects, can lead to amnesia and respiratory issues; and while ketamine has anesthetic properties, it does not typically cause hyperthermia as a major risk factor. Thus, MDMA stands out for its association with severe hyperthermic syndrome and the subsequent complications, including kidney failure.