alosetron hydrochloride
(ah loss' e tron)
Lotronex

Pregnancy Category B

Drug class
5-HT3 antagonist

Therapeutic actions
Blocks 5-HT3 (serotonin) receptors in the enteric nervous system of the gastrointestinal tract; interacting with these receptors blocks visceral sensitivity, increases colonic transit time, decreases GI motility, may also decrease the perception of abdominal pain and discomfort.

Indications
· Treatment of severe diarrhea-predominant irritable bowel syndrome (IBS) in women who have chronic IBS (longer than 6 mo), have no anatomic or biochemical abnormalities of the GI tract, and who have failed to respond to conventional therapy.

Contraindications and cautions
· Contraindicated in the presence of hypersensitivity to the drug, history of chronic or severe constipation or sequelae from constipation; history of intestinal obstruction, stricture, toxic megacolon, GI perforation or adhesions; history of ischemic colitis, impaired intestinal circulation, thrombophlebitis, or hypercoagulable state; history of or current Crohn’s disease, ulcerative colitis, diverticulitis; inability to understand or comply with the Physician–Patient Agreement.
· Use caution in the presence of pregnancy, lactation, and with elderly patients.

Available forms
Tablets--1 mg

Dosages
ADULTS
1 mg/day PO for 4 wk; may be continued if drug is tolerated and symptoms of IBS are under adequate control. Dose may be increased up to 1 mg bid PO after 4 wk if well tolerated.
PEDIATRIC PATIENTS
Safety and efficacy not established for children < 18 yr.
GERIATRIC PATIENTS OR PATIENTS WITH HEPATIC IMPAIRMENT
These patients may be at increased risk for toxicity; monitor very closely.

Pharmacokinetics
Route
Onset
Peak
PO
Rapid
1 hr

Metabolism: Hepatic; T1/2: 1.5 hr
Distribution: Crosses placenta; enters into breast milk
Excretion: Urine and bile

Adverse effects
· CNS: Anxiety, tremors, dreams, headache
· Dermatologic: sweating, urticaria
· GI: Abdominal pain, nausea, constipation, ischemic colitis
· Other: Malaise, fatigue, pain

Interactions
Drug-drug
· Increased risk of constipation if taken with other drugs that cause decreased GI motility. If this combination cannot be avoided, monitor patient very carefully and discontinue drug at first sign of constipation or ischemic colitis.

Nursing considerations
Assessment
· History: Presence of hypersensitivity to the drug, history of chronic or severe constipation or sequelae from constipation; history of intestinal obstruction, stricture, toxic megacolon, GI perforation or adhesions; history of ischemic colitis, impaired intestinal circulation, thrombophlebitis, or hypercoagulable state; history of Crohn’s disease, ulcerative colitis, diverticulitis; inability to understand or comply with the Physician–Patient Agreement, pregnancy, lactation, elderly patients.
· Physical: Skin lesions; body temperature; reflexes, affect; urinary output, abdominal exam; bowel patterns

Interventions
· Ensure that the patient has read and understands the Physician–Patient Agreement outlining the risks associated with the use of the drug and warning signs to report.
· Ensure that the Physician–Patient Agreement is in the patient’s permanent record.
· Administer drug without regard to food.
· Arrange for further evaluation of patient after 4 wk of therapy to determine effectiveness of drug.
· Encourage the use of barrier contraceptives to prevent pregnancy while on this drug.
· Maintain supportive treatment as appropriate for underlying problem.
· Provide additional comfort measures to alleviate discomfort from GI effects, headache, etc.
· Monitor patient for any signs of constipation; discontinue drug at first sign of constipation or ischemic colitis and alert the prescribing physician.

Teaching points
· Read and sign the Physician–Patient Agreement, which outlines the risks and benefits of therapy with this drug.
· Arrange to have regular medical follow-up while you are on this drug.
· Use barrier contraceptives while on this drug; serious adverse effects could occur during pregnancy; if you become or wish to become pregnant, consult with your physician.
· Be aware that these side effects may occur: headache (consult with your health care provider if these become bothersome, medications may be available to help); nausea, vomiting (proper nutrition is important, consult with your dietician to maintain nutrition).
· Maintain all of the usual activities and restrictions that apply to your condition. If this becomes difficult, consult with your health care provider.
· Report: constipation, signs of ischemic colitis--worsening abdominal pain, bloody diarrhea, blood in the stool; continuation of IBS symptoms without relief.

Adverse effects in Italic are most common; those in Bold are life-threatening.