dolasetron mesylate

Action

Blocks serotonin activation at receptor sites in vagal nerve terminals and in chemoreceptor trigger zone in CNS, decreasing the vomiting reflex

Availability

Injection: 12.5 mg/0.625-ml ampules, 20 mg/ml in 5-ml vials

Tablets: 50 mg, 100 mg

Indications and dosages

➣ Chemotherapy-induced nausea and vomiting

Adults: 100 mg P.O. 1 hour before chemotherapy or 1.8 mg/kg I.V. 30 minutes before chemotherapy

Children ages 2 to 16: 1.8 mg/kg P.O. within 1 hour before chemotherapy or 1.8 mg/kg I.V. (not to exceed 100 mg) 30 minutes before chemotherapy

➣ Prevention or treatment of postoperative nausea and vomiting

Adults: 100 mg P.O. within 2 hours before surgery or 12.5 mg I.V. 15 minutes before cessation of anesthesia (for prevention) or as soon as nausea or vomiting begins (for treatment)

Children ages 2 to 16: 1.2 mg/kg P.O. (up to 100 mg/dose) within 2 hours before surgery or 0.35 mg/kg I.V. (up to 12.5 mg) 15 minutes before cessation of anesthesia (for prevention) or as soon as nausea or vomiting begins (for treatment)

Contraindications

• Hypersensitivity to drug

• Arrhythmias

Precautions

Use cautiously in:

• risk factors for prolonged cardiac conduction intervals

• pregnant or breastfeeding patients (safety not established).

Administration

• Give oral dose at least 1 hour before chemotherapy for best results.

• To prevent postoperative nausea, give oral dose within 2 hours before surgery.

• If patient has difficulty swallowing tablet, injection solution may be mixed with apple or apple-grape juice and given orally.

• For I.V. use, give 100 mg single dose undiluted over 30 seconds. For I.V. infusion, dilute in normal saline solution, dextrose 5% in water, or lactated Ringer's solution to 50 ml, and give single dose over at least 15 minutes. Don't mix with other drugs.

• Flush I.V. line before and after infusion.

Adverse reactions

CNS: headache (increased in cancer patients), dizziness, fatigue, syncope

CV: bradycardia, tachycardia, ECG changes, hypertension, hypotension

GI: diarrhea, constipation, dyspepsia, abdominal pain

GU: urinary retention, oliguria

Skin: pruritus, rash

Other: chills, fever, decreased appetite

Interactions

Drug-drug. Antiarrhythmics, anthracycline (high cumulative doses), diuretics, drugs that prolong QTc interval: increased risk of conduction abnormalities

Drugs that affect hepatic microsomal enzymes: altered dolasetron blood level

Drug-diagnostic tests. Alanine aminotransferase, aspartate aminotransferase: increased levels

Patient monitoring

• Monitor closely for excessive diuresis.

See Watch for ECG changes, including prolonged PR interval and widened QRS complex, especially in patients receiving antiarrhythmics concurrently.

Patient teaching

• Instruct patient to take drug 1 to 2 hours before chemotherapy.

• Inform patient that drug commonly causes headache.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.