Ondansetron dosage

Ondansetron - Little information is available about dosage in children 3 years of age or younger. 

All 5HTj-receptor antagonists are metabolised by the liver, but, with the exception of ondansetron, no dosage adjustments are recommended for the treatment of acute nausea. However, in patients with chronic nausea the dosage of 5HTj-receptor antagonist should be reduced to prevent accumulation of the parent drug and any active (or inactive) metabolites. 

Ondansetron can cause extrapjramidal reactions (34). In two cases the reaction did not recur after a reduction in dosage or a change in the infusion time. 

Ondansetron (OND), a. S-hydroxytryptaminej receptor antagonist, has been used for prevention of nausea and vomiting associated with emetogenic cancer therapy. In view of the condition being treated, intravenous and oral dosage forms of OND may be inconvenient and/or unfeasible for specific patient populations. The nasal cavity can be a potential alternative route. A dose of 1 mg/kg OND (Zofran injection, 2 mg/mL) was administered to male Sprague-Dawley rats intravenously or intranasally. The peak plasma level of OND was attained within 10 min after application to the nasal mucosa of the rat. The plasma concentration-time profiles for nasal administration were comparable to those for intravenous injection, indicating complete absorption via the nasal route. The terminal elimination half-lives of the two routes of administration were also similar. The nasal administration route of OND was superior to the oral route (in humans, the oral absolute bioavailability is only 56% and the time to peak concentration is 1.0-2.Ih) and as effective as the intravenous route. 

The incidence and severity of vomiting depends on the dosage and route of administration of antineoplastic agents. Intravenous ondansetron (Zof-ran) plus dexamethasone and lorazepam is the most effective treatment available for prevention of severe vomiting due to antineoplastic agents (see also Figure 73). 

Metoclopramide pre-treatment reduces the dosage requirements of propofol and thiopental. Droperidol, but not ondansetron, reduces the dose requirements of thiopentaL... 

No important pharmacokinetic interactions occur, therefore no dosage adjustment is required when aprepitant is given with dolasetron, ondansetron, granisetron or palonosetron. 

Bozigian HP, Pritchard JP, Gooding AE, Pakes GE. Ondansetron absorption in adults effect of dosage form, food, and antacids. JPharm Sci (1994) 83, 1011-13. 

Potent P450 inducers, including phenytoin, rifampicin, and carbamazepine, can significantly increase the clearance and decrease the blood concentration of ondansetron. However, there are not sufficient data to support dosage adjustment for patients taking these drugs. 

Drug overdose Severe toxicity occurred in a 12-month-old boy who unintentionally took 7 or 8 tablets of ondansetron 8 mg (5.6-6.4 mg/kg against a therapeutic dosage of 0.15 mg/kg), and developed obtundation and myoclonic movements of the limbs... 

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