General Articles


Sound-alike/look-alike issues:
Lotronex® may be confused with Lovenox®, Protonix®

International issues:
Lotronex® may be confused with Lotanax® which is a brand name for terfenadine in the Czech Republic

MEDICATION GUIDE — An FDA-approved patient medication guide, which is available with the product information and at, must be dispensed with this medication for each new outpatient prescription and refill.

U.S. BRAND NAMES — Lotronex®

Selective 5-HT3 Receptor Antagonist

DOSING: ADULTS — IBS: Female: Oral: Initial: 0.5 mg twice daily for 4 weeks, with or without food; if tolerated, but response is inadequate, may be increased after 4 weeks to 1 mg twice daily. If response is inadequate after 4 weeks of 1 mg twice-daily dosing, discontinue treatment.
Note: Discontinue immediately if constipation or signs/symptoms of ischemic colitis occur. Do not reinitiate in patients who develop ischemic colitis.

DOSING: ELDERLY — Refer to adult dosing. Dosage adjustment is not required; however, postmarketing experience suggests that elderly patients may be at greater risk for complications of constipation.

DOSING: RENAL IMPAIRMENT — The need for dosage adjustment has not been defined (due to limited information on activity of metabolites).

DOSING: HEPATIC IMPAIRMENT — In mild-to-moderate dysfunction (Child-Pugh score ≤ 9), use caution. Contraindicated in severe hepatic dysfunction (Child-Pugh score ≥ 10).

DOSAGE FORMS — Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Lotronex®: 0.5 mg, 1 mg

Lotronex®: 0.5 mg, 1 mg


ADMINISTRATION — May be administered with or without food; however, when administered with food, absorption may be reduced by approximately 25%.

USE — Treatment of women with severe diarrhea-predominant irritable bowel syndrome (IBS) who have failed to respond to conventional therapy

>10%: Gastrointestinal: Constipation (dose related; 29%)

2% to 10%: Gastrointestinal: Abdominal discomfort and pain (7%), nausea (6%), gastrointestinal discomfort and pain (5%), abdominal distention (2%), hemorrhoids (2%), regurgitation and reflux (2%)


≤ 1% (Limited to important or life-threatening): Allergic skin reactions, alopecia, anxiety, arrhythmia, bilirubin level changes, bladder inflammation, bone pain, breathing disorder, cholecystitis, cognitive function disorders, confusion, cramps, colitis, depression, dermatitis, diaphoresis, diverticulitis, dyspepsia, extrasystoles, fatigue, fluid disturbances, gastroenteritis, GI impaction, GI intussusception, GI lesions, GI motility decreased, GI obstructions, GI perforation, GI spasms, GI ulceration, headache, hematoma, hemorrhage, hepatitis, hyperacidity, hyper-/hypoglycemia, hypertension, hypnagogic effects, hypoesthesia, hypothalamus/pituitary dysfunction, ileus, ischemic colitis, memory effects, muscle pain/stiffness, occult stools, pain, proctitis, rash, RBC/hemoglobin defects, sedation, sexual dysfunction, skeletal pain, small bowel mesenteric ischemia, tachyarrhythmia, temperature regulation impairment, tremor, ulcerative colitis, urinary frequency, urticaria

CONTRAINDICATIONS — Do not start treatment in patients who are constipated. Hypersensitivity to alosetron or any component of the formulation; history of severe or chronic constipation or sequelae from constipation; history of ischemic colitis, intestinal obstruction, stricture, toxic megacolon, gastrointestinal perforation and/or adhesions; diverticulitis, current or history of Crohn’s disease, or ulcerative colitis; severe hepatic impairment; history of impaired intestinal circulation, thrombophlebitis, or hypercoagulable state; patients unable to understand or comply with “Patient-Physician” agreement; concomitant administration with fluvoxamine

Boxed warnings: Appropriate use: See “Other warnings/precautions” below. Constipation: See “Concerns related to adverse effects” below. Ischemic colitis: See “Concerns related to adverse effects” below. Patient-Physician agreement: See “Other warnings/precautions” below.

Concerns related to adverse effects: Constipation: [U.S. Boxed Warning]: Discontinue immediately in patients who develop constipation; serious complications of constipation have been infrequently reported (obstruction, ileus, perforation, impaction, toxic megacolon, secondary ischemia). Constipation is a frequent, dose-related side effect; risk for complications from constipation may be increased in elderly, debilitated patients, or with concurrent use of other medications which decrease GI motility. Nonsevere constipation may be managed by temporarily interrupting therapy. Do not initiate in patients with constipation. Do not initiate in patients with constipation. Ischemic colitis: [U.S. Boxed Warning]: Acute ischemic colitis has been reported during treatment. Discontinue and evaluate immediately in patients who experience rectal bleeding or a sudden worsening of abdominal pain, and do not restart therapy if ischemic colitis is diagnosed.

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Disease-related concerns: Hepatic impairment: Use caution in mild-to-moderate hepatic impairment (Child-Pugh score ≤ 9); contraindicated in severe impairment (Child-Pugh score ≥ 10).

Special populations: Elderly: Use with caution in the elderly due to increased risk of complications from constipation. Males: Safety and efficacy have not been established in males. Pediatrics: Safety and efficacy have not been established in children.

Other warnings/precautions: Appropriate use: [U.S. Boxed Warning]: Only indicated for women with severe diarrhea-predominant irritable bowel syndrome with inadequate response to conventional therapy. Patient-Physician agreement: [U.S. Boxed Warning]: Should only be prescribed by physicians enrolled in the Prometheus’ Prescribing Program for Lotronex®. Patients must read and sign a “Patient-Physician” agreement before receiving the initial prescription.

RESTRICTIONS — Only physicians enrolled in Prometheus’ Prescribing Program for Lotronex® may prescribe this medication. Program stickers must be affixed to all prescriptions; no phone, fax, or computerized prescriptions are permitted with this program.

METABOLISM / TRANSPORT EFFECTS — Substrate of CYP1A2 (major), 2C9 (minor), 3A4 (minor); Inhibits CYP1A2 (weak), 2E1 (weak)

Apomorphine: Antiemetics (5HT3 Antagonists) may enhance the hypotensive effect of Apomorphine. Risk X: Avoid combination

CYP1A2 Inhibitors (Moderate): May decrease the metabolism of CYP1A2 Substrates. Risk C: Monitor therapy

CYP1A2 Inhibitors (Strong): May decrease the metabolism of CYP1A2 Substrates. Risk D: Consider therapy modification

CYP3A4 Inhibitors (Strong): May increase the serum concentration of Alosetron. Risk C: Monitor therapy

Fluvoxamine: May decrease the metabolism of Alosetron. Risk X: Avoid combination

Rifamycin Derivatives: May increase the metabolism of Antiemetics (5HT3 Antagonists). Risk C: Monitor therapy

ETHANOL / NUTRITION / HERB INTERACTIONS — Food: When administered with food, absorption may be reduced by ~25%.


PREGNANCY IMPLICATIONS — There are no adequate and well-controlled studies in pregnant women. Alosetron should be used in pregnant women only if clearly needed.

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LACTATION — Excretion in breast milk unknown/use caution

BREAST-FEEDING CONSIDERATIONS — Animal studies indicate that alosetron and/or metabolites are excreted in breast milk.

It is not known if alosetron in excreted in human milk. Caution should be used in administering alosetron to a nursing woman.

DIETARY CONSIDERATIONS — May be taken with or without food.

PRICING — (data from
Tablets (Lotronex)
1 mg (30): $428.32

MECHANISM OF ACTION — Alosetron is a potent and selective antagonist of a subtype of the serotonin 5-HT3 receptor. 5-HT3 receptors are ligand-gated ion channels extensively distributed on enteric neurons in the human gastrointestinal tract, as well as other peripheral and central locations. Activation of these channels affect the regulation of visceral pain, colonic transit, and gastrointestinal secretions. In patients with irritable bowel syndrome, blockade of these channels may reduce pain, abdominal discomfort, urgency, and diarrhea.

Distribution: Vd: 65-95 L

Protein binding: 82%

Metabolism: Extensive hepatic metabolism. Alosetron is metabolized by CYP2C9, 3A4, and 1A2. Thirteen metabolites have been detected in the urine. Biological activity of these metabolites in unknown.

Bioavailability: Mean: 50% to 60% (range: 30% to >90%); decreased with food (25%)

Half-life elimination: 1.5 hours for alosetron

Time to peak: 1 hour after oral administration

Excretion: Urine (73%) and feces (24%); 7% as unchanged drug (1% feces, 6% urine)

PATIENT INFORMATION — Take with or without food. Do not take if you are frequently constipated; constipation is a side effect associated with this medication and can lead to serious complications. Stop taking this medication and call your prescriber if you become constipated, or if you have sudden worsening of abdominal pain, severe constipation, or blood in your stool. Do not continue taking the medication until you have spoken with your prescriber; if after stopping the medication, constipation does not resolve, call your prescriber again. Notify your prescriber if you are pregnant, plan on becoming pregnant, or if you are breast-feeding.