The influence of renal impairment on the pharmacokinetics of haloperidol has not been evaluated. About one-third of a haloperidol dose is excreted in urine, mostly as metabolites. Less than 3% of administered haloperidol is eliminated unchanged in the urine. Haloperidol metabolites are not considered to make a significant contribution to its activity, although for the reduced metabolite of haloperidol, back-conversion to haloperidol cannot be fully ruled out. Even though impairment of renal function is not expected to affect haloperidol elimination to a clinically relevant extent, caution is advised in patients with renal impairment, and especially those with severe impairment, due to the long half-life of haloperidol and its reduced metabolite, and the possibility of accumulation (see section ).
In sedative-hypnotic detoxification, the patient is prescribed an equivalent dosage of phenobarbital ( Table 6 ) . 5 Phenobarbital is preferred because it has a long half-life and thus does not have to be covered for its own subsequent withdrawal state. The duration of the detoxification program is determined by the drug that has been abused. The patient who has abused a short-acting sedative-hypnotic drug such as alprazolam or zolpidem can be detoxified in seven to 10 days, whereas the patient who has abused an intermediate-acting sedative-hypnotic such as diazepam, phenobarbital or glutethimide requires 10 to 14 days of detoxification.