LOTRONEX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for LOTRONEX (LOTRONEX).

How it works

Selective serotonin 5-HT3 receptor antagonist; blocks serotonin action in the GI tract, reducing intestinal motility and visceral hypersensitivity.

What the body does with it

Metabolism	Hepatic metabolism via cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP3A4, CYP2D6); also metabolized by aldehyde oxidase.
Excretion	Alosetron is primarily eliminated via hepatic metabolism with subsequent renal excretion of metabolites. Approximately 73% of a dose is recovered in urine (mostly metabolites) and 24% in feces.
Half-life	The terminal elimination half-life is approximately 1.5 to 2 hours in healthy individuals. In patients with hepatic impairment, half-life may be prolonged.
Protein binding	Alosetron is approximately 82% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
Volume of Distribution	The volume of distribution (Vd) is approximately 1.0 L/kg (65-95 L in adults), indicating extensive tissue distribution.
Bioavailability	Oral bioavailability is approximately 50-60% due to first-pass hepatic metabolism. Absorption is rapid with peak plasma concentrations at 1 hour post-dose.
Onset of Action	Onset of action for symptom relief (diarrhea-predominant IBS) is typically within 1-2 weeks of oral dosing, though clinical trials show improvement as early as 1 week.
Duration of Action	Duration of action following oral administration is about 8-12 hours, corresponding to the dosing interval of 4-12 mg daily. Symptom control is maintained with regular dosing.

Classification & Brands

Dosing & administration

1 mg orally once daily for 4 weeks, then may increase to 1 mg twice daily if tolerated; maximum 1 mg twice daily.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild-to-moderate renal impairment; not studied in severe renal impairment (CrCl <15 mL/min).
Liver impairment	Contraindicated in Child-Pugh class A, B, or C; not recommended in any degree of hepatic impairment.
Pediatric use	Safety and efficacy not established; no recommended dosing.
Geriatric use	No specific dose adjustment recommended; use with caution due to increased risk of constipation in elderly.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for LOTRONEX (LOTRONEX).

Breastfeeding	Unknown if excreted in human breast milk. Caution advised due to potential for serious adverse effects (e.g., constipation, ischemic colitis). M/P ratio not available.
Teratogenic Risk	Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; risk cannot be excluded. Use only if clearly needed during pregnancy, especially first trimester.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Increased risk of serious gastrointestinal adverse events, including ischemic colitis and complicated complications of constipation, which may require hospitalization and rarely lead to surgery or death. LOTRONEX should be prescribed only by physicians enrolled in the Prescribing Program.

Side Effect Profile

Serious Effects

Absolute Contraindications

["History of chronic or severe constipation","History of ischemic colitis","History of intestinal obstruction, stricture, toxic megacolon, or perforation","History of Crohn's disease or ulcerative colitis","Current or history of diverticulitis","Concurrent use of drugs that inhibit CYP1A2 (e.g., fluvoxamine)"]

Clinical Precautions

Precautions

["Ischemic colitis","Complicated constipation (including obstruction, perforation, impaction)","Use with caution in patients with hepatic impairment","Avoid in patients with active or chronic constipation","Monitor for signs of ischemic colitis or complicated constipation"]

Clinical Tips & Counseling

Drug interactions

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LOTRONEX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for LOTRONEX (LOTRONEX).

How it works

Selective serotonin 5-HT3 receptor antagonist; blocks serotonin action in the GI tract, reducing intestinal motility and visceral hypersensitivity.

What the body does with it

Metabolism	Hepatic metabolism via cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP3A4, CYP2D6); also metabolized by aldehyde oxidase.
Excretion	Alosetron is primarily eliminated via hepatic metabolism with subsequent renal excretion of metabolites. Approximately 73% of a dose is recovered in urine (mostly metabolites) and 24% in feces.
Half-life	The terminal elimination half-life is approximately 1.5 to 2 hours in healthy individuals. In patients with hepatic impairment, half-life may be prolonged.
Protein binding	Alosetron is approximately 82% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
Volume of Distribution	The volume of distribution (Vd) is approximately 1.0 L/kg (65-95 L in adults), indicating extensive tissue distribution.
Bioavailability	Oral bioavailability is approximately 50-60% due to first-pass hepatic metabolism. Absorption is rapid with peak plasma concentrations at 1 hour post-dose.
Onset of Action	Onset of action for symptom relief (diarrhea-predominant IBS) is typically within 1-2 weeks of oral dosing, though clinical trials show improvement as early as 1 week.
Duration of Action	Duration of action following oral administration is about 8-12 hours, corresponding to the dosing interval of 4-12 mg daily. Symptom control is maintained with regular dosing.

Classification & Brands

Dosing & administration

1 mg orally once daily for 4 weeks, then may increase to 1 mg twice daily if tolerated; maximum 1 mg twice daily.

Dosage form	TABLET
Renal impairment	No dose adjustment required for mild-to-moderate renal impairment; not studied in severe renal impairment (CrCl <15 mL/min).
Liver impairment	Contraindicated in Child-Pugh class A, B, or C; not recommended in any degree of hepatic impairment.
Pediatric use	Safety and efficacy not established; no recommended dosing.
Geriatric use	No specific dose adjustment recommended; use with caution due to increased risk of constipation in elderly.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for LOTRONEX (LOTRONEX).

Breastfeeding	Unknown if excreted in human breast milk. Caution advised due to potential for serious adverse effects (e.g., constipation, ischemic colitis). M/P ratio not available.
Teratogenic Risk	Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; risk cannot be excluded. Use only if clearly needed during pregnancy, especially first trimester.
Fetal Monitoring