ZELNORM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZELNORM (ZELNORM).
Tegaserod is a partial agonist at the 5-HT4 receptor, increasing peristalsis and gastrointestinal motility.
| Metabolism | Metabolized via hydrolysis and direct glucuronidation; CYP450 plays a minor role (CYP2C9 and CYP3A4). |
| Excretion | Primarily fecal (approximately 65% as unchanged drug) and renal (approximately 30% as unchanged drug and metabolites). |
| Half-life | Terminal elimination half-life is approximately 6.0 ± 1.6 hours in healthy volunteers; no significant accumulation with twice-daily dosing. |
| Protein binding | Approximately 98% bound primarily to serum albumin and α1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution is approximately 50–100 L (not reported as L/kg in literature; estimated ~1 L/kg based on 70 kg), indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability is approximately 10% due to extensive first-pass metabolism; food does not significantly affect absorption. |
| Onset of Action | Oral: Onset of clinical effect (improvement in bowel symptoms) typically occurs within 1 week; initial effect may be seen within 24 hours. |
| Duration of Action | Duration of action persists throughout the dosing interval (12 hours); symptomatic improvement requires continued dosing. |
| Molecular Weight | 340.46 |
6 mg orally three times daily, at least 30 minutes before meals.
| Dosage form | TABLET |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (GFR <30 mL/min); use not recommended. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: 2 mg orally three times daily. Child-Pugh Class C: contraindicated. |
| Pediatric use | Safety and efficacy not established in pediatric patients (age <18 years). |
| Geriatric use | No specific dose adjustment recommended; caution due to potential for increased systemic exposure and higher risk of adverse events. |
| 1st trimester | No adequate studies in pregnant women; use only if benefit outweighs risk. Animal studies show some teratogenicity at high doses. |
| 2nd trimester | No adequate studies; consider risk-benefit. Animal studies show fetal toxicity at high doses. |
| 3rd trimester | No adequate studies; avoid use near term due to potential for uterine contractions. |
Clinical note
Comprehensive clinical and safety monograph for ZELNORM (ZELNORM).
| Placental transfer | Crosses placenta in animals; human data limited but expected to cross due to low molecular weight. |
| Breastfeeding | Excretion into human milk unknown; due to potential for serious adverse reactions in nursing infants, decision should be made to discontinue nursing or drug, considering importance of drug to mother. |
■ FDA Black Box Warning
Increased risk of ischemic cardiovascular events including myocardial infarction, stroke, and unstable angina. Contraindicated in patients with a history of cardiovascular disease or risk factors.
| Serious Effects |
History of serious adverse reaction to tegaserodSevere renal impairment (CrCl <15 mL/min)Moderate or severe hepatic impairment (Child-Pugh class B or C)History of bowel obstruction, symptomatic gallbladder disease, or sphincter of Oddi dysfunctionHistory of abdominal adhesionsConcurrent use of MAO inhibitors
| Precautions | Cardiovascular ischemic events; diarrhea; hypotension; ischemic colitis; gallbladder dysfunction; drug interactions with MAOIs and SSRIs (serotonin syndrome risk). |
| Food/Dietary | Take on an empty stomach to maximize absorption. Avoid high-fat meals as they can reduce drug levels. No specific food interactions, but maintain adequate hydration to counteract diarrhea. |
Loading safety data…
| Lactation Rating |
| L4 (Possibly Hazardous) |
| Teratogenic Risk | Pregnancy Category B. Animal studies have not demonstrated fetal risk; no adequate human studies in first trimester. Due to limited data, use only if clearly needed. No known teratogenicity. |
| Fetal Monitoring | Monitor for severe diarrhea, hypokalemia, dehydration, and electrolyte disturbances; assess fetal growth and well-being if maternal condition compromised. |
| Fertility Effects | No known adverse effects on fertility in animal studies; human data lacking. |
| Clinical Pearls | Zelnorm (tegaserod) is a 5-HT4 receptor agonist used for irritable bowel syndrome with constipation (IBS-C) in women <65 years. Due to cardiovascular risks (MI, stroke), it is contraindicated in patients with a history of cardiovascular disease, arrhythmias, or QT prolongation. Monitor for ischemic cardiac events; discontinue if new symptoms arise. Avoid use in men and patients >65 years due to lack of efficacy data and increased risk. |
| Patient Advice | Take Zelnorm on an empty stomach, at least 30 minutes before meals. · Do not use if you have a history of heart attack, stroke, angina, or heart rhythm problems. · Seek immediate medical attention for chest pain, shortness of breath, or fainting. · Report severe diarrhea, abdominal pain, or rectal bleeding to your doctor. · Zelnorm is only for women under 65 with IBS-C; not for men or older women. |