[Indications and Clinical use]: For treatment and prevention of nausea and vomiting caused by cancer chemotherapy.
[Strength]: 50ml: 5mg Tropisetron and 0.9g Sodium Chloride
50ml: 2mg Tropisetron and 0.9g Sodium Chloride
[Indications]: Tropisetron hydrochloride is used by patients to prevent nausea and vomiting caused by surgery and cancer chemotherapy.
Tropisetron is well absorbed after oral doses. Peak plasma concentrations are achieved within 3 hours. Absolute bioavailability depends on the dose since first-pass metabolism is saturable. It is 71% bound to plasma proteins. Tropisetron is metabolised by hydroxylation and conjugation, and metabolites are excreted mainly in the urine with a small amount in the faeces. The cytochrome P450 isoenzyme CYP2D6 is involved in tropisetron metabolism, and shows genetic polymorphism.The elimination half-life is about 8 hours in extensive metabolisers and up to 45 hours in poor metabolisers. Clearance is also reduced in patients with renal impairment.
[Dosage and Administration]
Tropisetron is a 5-HT3 antagonist with an antiemetic action similar to that of ondansetron (p.1757). It is used in the prevention of nausea and vomiting induced by cytotoxic therapy and in the treatment and prevention of postoperative nausea and vomiting (p.1700). Tropisetron is given as the hydrochloride by slow intravenous injection or infusion, or orally. Doses are expressed in terms of tropisetron base; 5.64 mg of tropisetron hydrochloride is equivalent to about 5 mg of tropisetron base. For the prophylaxis of acute nausea and vomiting associated with cytotoxic chemotherapy a single dose of 5 mg may be given by slow intravenous injection or infusion on the day of treatment, shortly before chemotherapy.
The injection is given over not less than 1 minute; it may be given into a running infusion. For infusion, it is diluted into 100mL of a suitable infusion fluid (such as sodium chloride 0.9% or glucose 5%), and given over 15 minutes. Subsequent doses of 5 mg daily are given orally, in the morning at least one hour before food, for a further 5 days. Children over 2 years of age may be given 200 micrograms/kg (maximum dose 5 mg) before chemotherapy, by intravenous injection over at least 1 minute, or by infusion (at a concentration of 50 micrograms/mL in a suitable infusion fluid). In children weighing less than 25 kg the same dose may be given intravenously once daily for up to a further 4 days as required. In those weighing more than 25 kg, a dose of 5 mg may be given orally once daily for up to a further 5 days; if oral dosage is not possible the same dose may be given intravenously.
For the treatment of postoperative nausea and vomiting in adults 2 mg may be given by slow intravenous injection (over not less than 30 seconds), or by infusion (over 15 minutes), within 2 hours of the end of anaesthesia. For prophylaxis, the same dose may be given shortly before induction of anaesthesia.
Fatigue, abdominal pain, and diarrhoea may also occur. Visual hallucinations, and an increase in blood pressure in patients with preexisting hypertension, have been noted at high repeated doses. ECG changes such as prolongation of QT interval have been noted with high-dose intravenous tropisetron.
Carcinogenicity: the manufacturer (Novartis, UK) has reported an increased incidence of hepatic neoplasms in male mice given high doses of tropisetron but it is suggested that these effects are both species and sex specific.
The effects on the cardiovascular system: for a discussion of the effects of 5-HT3 antagonists on the cardiovascular system, Chest pain and/or cardiac arrhythmias that might have been associated with tropisetron hydrochloride were reported1 in 4 patients, 2 of whom died. In 3 subsequent patients who developed severe chest or anginal pain, treatment with tropisetron hydrochloride was stopped. The manufacturers (Glaxo) had at that time no evidence of a causal relationship between Tropisetron hydrochloride and episodes of chest pain and cardiac abnormalities.2 Giving tropisetron hydrochloride or granisetron intravenously produced no clinically important cardiovascular changes in a study in 12 healthy subjects.3 Since then, however, myocardial ischaemia has been reported with both tropisetron hydrochloride 4 and dolasetron; 5 in the latter case this led to an acute myocardial infarction. Supraventricular tachycardia reported with dolasetron was attributed to an interaction with sevoflurane.6. Another study in healthy subjects found that dolasetron mainly altered ECG parameters indicative of ventricular depolarisation, whereas tropisetron hydrochloride affected mainly ventricular repolarisation.7. However, ECG changes were transient and asymptomatic. Studies of high-dose intravenous granisetron8-10 found no significant adverse effects on pulse, blood pressure, or ECG measurements. A review11 of the electrocardiographic and although this class of drugs may cause small, transient ECG changes, the clinical benefits of the drugs outweighed the small theoretical risk of any clinically significant cardiovascular events. Nonetheless, the use of dolasetron in children has been contra-indicated in the UK.
The drug should therefore be used with caution in patients with cardiac rhythm or conduction disturbances. Care should be taken when driving or operating machinery. No dosage reduction is considered necessary in renal or hepatic impairment despite possible reductions in clearance.
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