EMADON SYRUP

Indications

• Nausea and vomiting associated with chemotherapy
• Nausea and vomiting associated with radiotherapy
• Prevention of postoperative nausea and vomiting

Dosage

Children: Refer to the BNF for Children for appropriate pediatric dosing guidelines.

Adults: Refer to the BNF for specific dosing recommendations based on the indication and patient characteristics.

Mechanism of action

Ondansetron works by selectively blocking 5-HT3 receptors, which are located in the central nervous system and the gastrointestinal tract. By inhibiting the binding of serotonin to these receptors, ondansetron reduces the occurrence of nausea and vomiting.

Pharmacodynamics

The pharmacodynamics of ondansetron involve its ability to prevent the activation of the vomiting reflex through antagonism of the 5-HT3 receptors. This action is particularly important in the context of chemotherapy-induced nausea and vomiting, where serotonin release from the enterochromaffin cells in the gut plays a significant role in triggering the vomit reflex. Ondansetron has a rapid onset of action and is effective in both acute and delayed phases of chemotherapy-induced nausea.

Pharmacokinetics

Ondansetron is well-absorbed after oral administration, with a bioavailability of approximately 60%. It undergoes extensive hepatic metabolism via the cytochrome P450 system, primarily CYP3A4, CYP2D6, and CYP1A2. The elimination half-life of ondansetron is about 3 to 6 hours, and it is primarily excreted in the urine as metabolites. It is important to note that the pharmacokinetics may vary in patients with hepatic impairment.

Contra-indications

• Hypersensitivity to ondansetron or any of its excipients
• Concomitant use with apomorphine (due to a risk of hypotension and loss of consciousness)

Adverse effects

• Headache
• Constipation
• Diarrhea
• Dizziness
• Fatigue
• Prolonged QT interval
• Serotonin syndrome (rare)

Interactions

• Caution with drugs that prolong the QT interval, such as certain antiarrhythmics and antipsychotics
• May enhance the effects of serotonergic drugs, increasing the risk of serotonin syndrome
• Reduced efficacy with rifampicin due to induction of cytochrome P450 enzymes

Precautions

• Use with caution in patients with a history of cardiac arrhythmias or electrolyte abnormalities
• Monitor for symptoms of serotonin syndrome when used with other serotonergic agents
• Consider alternative antiemetics in patients with phenylketonuria (PKU) if formulations contain aspartame

Pregnancy

Ondansetron should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. Consult local guidelines.

Breast-feeding

Ondansetron is excreted in breast milk, and caution is advised when administering to nursing mothers. Consult local guidelines.

Storage

Store in a cool, dry place away from light. Protect from moisture. Check specific product for storage details.

Formulations

• Tablets (oral)
• Oral solution
• Injectable (IV/IM)
• Orally disintegrating tablets