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In general, the signs and symptoms of overdosage with ORAP (pimozide) would be an exaggeration of known pharmacologic effects and adverse reactions, the most prominent of which would be: 1) electrocardiographic abnormalities, 2) severe extrapyramidal reactions, 3) hypotension, 4) a comatose state with respiratory depression.
In the event of overdosage, gastric lavage, establishment of a patent airway and, if necessary, mechanically-assisted respiration are advised. Electrocardiographic monitoring should commence immediately and continue until the ECG parameters are within the normal range. Hypotension and circulatory collapse may be counteracted by use of intravenous fluids, plasma, or concentrated albumin, and vasopressor agents such as metaraminol, phenylephrine and norepinephrine.
Epinephrine should not be used. In case of severe extrapyramidal reactions, antiparkinson medication should be administered. Because of the long half-life of pimozide, patients who take an overdose should be observed for at least 4 days. As with all drugs, the physician should consider contacting a poison control center for additional information on the treatment of overdose.
- ORAP (pimozide) is contraindicated in the treatment of simple tics or tics other than those associated with Tourette's Disorder.
- ORAP should not be used in patients taking drugs that may, themselves, cause motor and phonic tics (e.g., pemoline, methylphenidate and amphetamines) until such patients have been withdrawn from these drugs to determine whether or not the drugs, rather than Tourette's Disorder, are responsible for the tics.
- Because ORAP prolongs the QT interval of the electrocardiogram it is contraindicated in patients with congenital long QT syndrome, patients with a history of cardiac arrhythmias, patients taking other drugs which prolong the QT interval of the electrocardiogram or patients with known hypokalemia or hypomagnesemia (see also PRECAUTIONS: DRUG INTERACTIONS).
- ORAP is contraindicated in patients with severe toxic central nervous system depression or comatose states from any cause.
- ORAP is contraindicated in patients with hypersensitivity to it. As it is not known whether cross-sensitivity exists among the antipsychotics, pimozide should be used with appropriate caution in patients who have demonstrated hypersensitivity to other antipsychotic drugs.
- Ventricular arrhythmias have been rarely associated with the use of macrolide antibiotics in patients with prolonged QT intervals, as might be produced by ORAP. Specifically, two sudden deaths have been reported when clarithromycin was added to ongoing pimozide therapy. Furthermore, some evidence suggests that pimozide is metabolized partly by the enzyme system cytochrome P450 3A4 (CYP 3A4). Macrolide antibiotics are inhibitors of CYP 3A4, and thus could potentially impede pimozide metabolism. For these reasons, ORAP is contraindicated in patients receiving the macrolide antibiotics clarithromycin, erythromycin, azithromycin, dirithromycin, and troleandomycin.
- Concomitant use in patients taking Celexa or Lexapro is contraindicated (seePRECAUTIONS: DRUG INTERACTIONS - Pimozide and Celexa).
- Clinical drug interaction studies have demonstrated that pimozide is also metabolized by CYP 2D6. Concomitant use of ORAP with paroxetine and other strong CYP 2D6 inhibitors is contraindicated (SeePRECAUTIONS: DRUG INTERACTIONS).
- Concomitant use of pimozide in patients taking sertraline is contraindicated (SeePRECAUTIONS: DRUG INTERACTIONS).
Because azole antifungal agents are also inhibitors of the CYP 3A4 enzymes and thus may likewise impair pimozide metabolism, ORAP is contraindicated in patients receiving the azole antifungal agents itraconazole and ketoconazole.
Similarly, protease inhibitor drugs are also inhibitors of CYP 3A4, and thus ORAP is contraindicated in patients receiving protease inhibitors such as ritonavir, saquinovir, indinavir, and nelfinavir. (SeePRECAUTIONS: DRUG INTERACTIONS.)
Nefazodone is a potent inhibitor of CYP 3A4, and its concomitant use with ORAP is also contraindicated.
Other drugs that are relatively less potent inhibitors of CYP 3A4 should also be avoided, in view of the risks: e.g. zileuton, fluvoxamine.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 10/7/2011
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