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Zelnorm (Tegaserod Maleate) - Drug Interactions, Contraindications, Overdosage

 


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DRUG INTERACTIONS

In vitro drug-drug interaction data with tegaserod indicated no inhibition of the cytochrome P450 isoenzymes CYP2C8, CYP2C9, CYP2C19, CYP2E1 and CYP3A4, whereas inhibition of CYP1A2 and CYP2D6 could not be excluded. However, in vivo, no clinically relevant drug-drug interactions have been observed with dextromethorphan (CYP2D6 prototype substrate), and theophylline (CYP1A2 prototype substrate). There was no effect on the pharmacokinetics of digoxin, oral contraceptives, and warfarin. The main human metabolite of tegaserod hydrogen maleate, 5-methoxyindole-3-carboxylic acid glucuronide, did not inhibit the activity of any of the above cytochrome P450 isoenzymes in in vitro tests.

Dextromethorphan:    A pharmacokinetic interaction study demonstrated that co-administration of tegaserod and dextromethorphan did not change the pharmacokinetics of either compound to a clinically relevant extent. Dose adjustment of either drug is not necessary when tegaserod is combined with dextromethorphan. Therefore, tegaserod is not expected to alter the pharmacokinetics of drugs metabolized by CYP2D6 (e.g., fluoxetine, omeprazole, captopril).

Theophylline:    A pharmacokinetic interaction study demonstrated that co-administration of tegaserod and theophylline did not affect the pharmacokinetics of theophylline. Dose adjustment of theophylline is not necessary when tegaserod is co-administered. Therefore, tegaserod is not expected to alter the pharmacokinetics of drugs metabolized by CYP1A2 (e.g., estradiol, omeprazole).

Digoxin:    A pharmacokinetic interaction study with digoxin demonstrated that concomitant administration of tegaserod reduced peak plasma concentration and exposure of digoxin by approximately 15%. This reduction of bioavailability is not considered clinically relevant. When tegaserod is co-administered with digoxin dose adjustment is unlikely to be required.

Warfarin:    A pharmacokinetic and pharmacodynamic interaction study with warfarin demonstrated no effect of concomitant administration of tegaserod on warfarin pharmacokinetics and pharmacodynamics. Dose adjustment of warfarin is not necessary when tegaserod is co-administered.

Oral Contraceptives:    Co-administration of tegaserod did not affect the steady-state pharmacokinetics of ethinylestradiol and reduced peak concentrations and exposure of levonorgestrel by 8%. Tegaserod is not expected to alter the risk of ovulation in subjects taking oral contraceptives. No alteration in oral contraceptive medication is necessary when tegaserod is co-administered.

OVERDOSAGE

There have been no reports of human overdosage with Zelnorm® (tegaserod maleate). Single oral doses of 120 mg of tegaserod were administered to 3 healthy volunteers in 1 study. All 3 subjects developed diarrhea and headache. Two of these subjects also reported intermittent abdominal pain, and 1 developed orthostatic hypotension. In 28 healthy subjects exposed to doses of tegaserod of 90 to 180 mg/d for several days, adverse events were diarrhea (100%), headache (57%), abdominal pain (18%), flatulence (18%), nausea (7%) and vomiting (7%).

Based on the large distribution volume and high protein binding of tegaserod it is unlikely that tegaserod could be removed by dialysis. In cases of overdosage treat symptomatically and institute supportive measures as appropriate.

CONTRAINDICATIONS

Zelnorm® (tegaserod maleate) is contraindicated in those patients with:

  • severe renal impairment
  • moderate or severe hepatic impairment
  • a history of bowel obstruction, symptomatic gallbladder disease, suspected sphincter of Oddi dysfunction, or abdominal adhesions
  • a known hypersensitivity to the drug or any of its excipients

Page last updated: 2006-06-02

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