Ondansentron Injection

Drug Classification : Antiemetics
Compositions :
Ondansentron film coated caplet 8 mg, each film coated caplet contains : Ondansentron HCL equivalent to Ondansentron 8 mg
Ondansentron injection, each ml conatains : Ondansentron HCL equivalent to Ondansentron 2 mg

Pharmacology :
Pharmacodynamics :
Ondansentron is a potent, highly selective 5-HT3 receptor antagonist. Its precise mode of action in the control of nausea and vomiting is not known. Chemotherapeutic agents and radiotherapy may cause release of 5-HT in the small intestine initiating a vomiting reflex by activating vagal afferents via 5-HT3 receptors. Ondansntron biocks the initiation of this reflex. Activation of vagal afferents may cause a release of 5-HT in the area postrema, located on the floor of the 4th ventricle, and this also promote emesis through a central mechanism. Thus, the effect of Ondansentron in the management of the nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy is due to antagonism of 5-HT3 receptors on neurons located both in the peripheral and central nervous system.

Pharmacokinetics :
- Aborption :
Following oral administration of Ondansentron, absorption is rapid with maximum plasma concentrations of about 30 ng/ml be attained approximately 1,5 hours after an 8 mg dose. Similar concentration are achieved with in approximately 10 minutes of an 4 mg dose. The absolute oral bioavailability os Ondansentron is approximately 60%. Equivalent systemic exposure is achieved following i.m. and i.v. administration. The disposition of Ondansentron following oral i.m and i.v. dosing is similar with a terminal elimination half life of about 3 hours.
- Distribution :Aborption :
A steady state volume of distribution of about 140L.
- Metabolism :
Plasma protein binding is 70 – 76%
- Excretion :
Ondansentron is cleared from the systemic circulation predominatly by metabolism with < 5% of a dose excreted in the urine. Indications : Management of nausea and vomiting induced by chemotherapy, radiotherapy and surgery. Dosage And Adminstration : Phrophylaxis os pst surgical nausea and vomiting : Initial dose is 8 mg orally given 1hr prior to anaesthesia followed by 20 further doses of 8 mg at 8 hourly intervals. Alternatively a single dose of 4 mg i.m. or slow i.v. injection. Preventive of nausea and vomiting due to chemotherapy : - Adults : • Very emotogenic chemotherapeutic agents eg. Cisplatin. Initially 8 mg by slow i.v. injection or infusion for 15 minutes before chemotherapy, then follwed by continuous infusion of 1mg/hours for 24 hours or injection of 8 mg by slow i.v. for 15 minutes at 4 hours intervals or also may be followed by 8 mg orally 2 times daily for < 5 days. • Less emetogenic chemotherapeutic agents eg. Cyclophosphamide 8 mg by slow i.v. injection or infusion for 15 minutes before chemotheraphy, then followed by 8 mg orally 2 times daily for < 5 days. • Nausea and vomiting due radiotherapy : 8 mg tablet 3 times daily 1 – 2 hours before radiotherapy. Duration of treatment depends on duration of radiotherapy. - Children > 4 years :
• 5 mg/ml i.v. for 15 minutes before chemotheraphy, followed by 4 mg orally every 12 hours for < 5 days. - Elderly : • Ondansentron can be well tolerated without dose adjustment in patients > 65 years old and no alleration of dosage, dosing frequency or route of administration are required.
- Patient with Impaired renal function :
• Dose adjustment is not required, dosing frequency or route of administration are required.
- Patient with Impaired liver function :
• Total daily dose should not exceed mg.


Contraindication :
- Patient with hypersensitivy to any componed of Ondansentron.

Warning And Precaution :
- Ondansentron should not be use during pregnancy, especially during the 1 st. trisemester, unless the expected benefit t the patient is throught to outweight any possible risk to the fetus.
- It is recommended that’s mther recelving Ondansentro should not breastfeed their babies.

Drug Interactions :
- Since Ondansentron is metabolized by cytochrome P-450 metabolic enzymes, inhibition or reduced activity of this enzyme change Ondansentron clearance and half life.
- In patients treated with potent inducers of CYP3A4 ( i.e. phenytoin, carbamazepine, and rifampicin ), the clearance of Ondansentron was increased and Ondansentron blood concentrations were decreased.

Adverse Reactions :
- Headache, a sensation of flushing or warmth in the head epigastrium and occasional transient, asymptomatic increases in aminotransferases, increase large bowel transit time and may cause constipation in samo patients.
- There have been rare reports of immediate hypersnsitivy reactions incliding anaphytaxis. Rare case of transient visual disturbances ( e.g blurred vision ) and dizziness have beeb reported during rapid i.v. administration of Ondansentron. There have been rare reports suggestive of involuntary movement disorders without definite evidence of persistent clinical sequelae.

Presentations :
- Ondansentron film coated cablet 8 mg : Box. 3 Blisters @ 10 coated caplet.
- Ondansentron Injection 2 mg/ml : Box. 5 ampoules @ 2 ml
Box. 5 ampoules @ 4 ml