Ondansetron

Introduction

Ondansetron , also known as Zofran, is an anti-emetic drug used to prevent nausea and vomiting associated with certain cancer treatments, surgeries, and other medical conditions. It is commonly used to help manage the adverse effects of chemotherapy, radiation therapy, and opioid-induced nausea in cancer patients.

Uses for

Ondansetron is primarily used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and opioid-induced nausea. It is also used to prevent nausea and vomiting after surgery and as a last resort in cases of severe morning sickness.

Brand Name	Ondansetron
Type
Weight
Generic	Ondansetron
Manufacturer
Available in	English বাংলা

Mechanism of Action

Ondansetron works by blocking the action of serotonin, a chemical released in the brain to trigger the vomiting reflex. It works by blocking the binding of serotonin to certain receptors in the brain, thus preventing the body from responding to the chemical and causing nausea and vomiting.

How Long Does It Take to Work?

Ondansetron usually begins to work within 30 minutes to 1 hour after taking the medication but may take longer to achieve the full effect. It is best to take the medication on an empty stomach and drink plenty of fluids. Consult your healthcare provider for the best timing for taking this medication.

Absorption

Ondansetron is well absorbed after oral administration. After an oral dose, bioavailability is approximately 56%. Peak plasma levels occur approximately 2-3 hours after administration.

Route of Elimination

Ondansetron is eliminated mainly by the kidneys, with only about 8% being excreted unchanged in the urine. The remainder is metabolized by the liver.

Dosage

Chemotherapy-Induced Nausea and Vomiting-
Adults, Pediatric patients (6 months to 18 years):

8 mg tablet/orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
4 mg orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
Injection: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose, infused intravenously over 15 minutes.

Radiotherapy-Induced Nausea and Vomiting-
Adults:

8 mg tablet/orodispersible tablet: Initial Dose: 8 mg orally 1 to 2 hours before radiotherapy. Post Radiotherapy: 8 mg orally every 8 hours for up to 5 days after a course of treatment.
4 mg orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
Injection: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose, infused intravenously over 15 minutes.

Postoperative Nausea and Vomiting-
Adults:

8 mg tablet/orodispersible tablet: 16 mg given as two 8 mg tablets
4 mg orodispersible tablet: 16 mg
Injection: 4 mg

Pediatrics (>40 kg): Injection: 4 mg
Pediatrics (40 kg): Injection: 0.1 mg/kg

Chemotherapy-induced Nausea and Vomiting-
Adults/Geriatric/Child of 12 years or over:

Highly emetogenic cancer chemotherapy: 30 ml (24 mg) Ondansetron Oral Solution administered 30 minutes before start of emetogenic chemotherapy.
Moderate emetogenic cancer chemotherapy: 10 ml (8 mg) Ondansetron Oral Solution administered 30 minutes before start of emetogenic chemotherapy. A further 10 ml dose should be administered after 8 hours of the first dose. One 10 ml dose should be administered twice a day (every 12 hours) for 1-2 days after completion of chemotherapy.

Pediatric (4-11 years): 5 ml (4 mg) Ondansetron Oral Solution should be taken 30 minutes before the start of chemotherapy. The other 2 doses should be taken 4 and 8 hours after the first dose. Then 5 ml oral solution should be administered 3 times a day (every 8 hours) for 1-2 days after completion of chemotherapy.

Oral solution:

Radiotherapy induced Nausea and Vomiting (Adults/Geriatric/Child of 12 years or over):

The recommended oral dosage: 10 ml (8 mg) Ondansetron Oral Solution 3 times daily.
For total body irradiation: 10 ml (8-mg) Ondansetron Oral Solution should be administered 1 to 2 hours before each fraction of radiotherapy administered each day.
For single high-dose fraction radiotherapy to the abdomen: one 10 ml Ondansetron Oral Solution should be administered 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for 1 to 2 days after completion of radiotherapy.
For daily fractionated radiotherapy to the abdomen: 10 ml (8-mg) Ondansetron Oral Solution should be administered 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for each day radiotherapy is given.

Postoperative Nausea and Vomiting (Adults/Geriatric/Child of 12 years or over):

20 ml (16 mg) Ondansetron Oral Solution 1 hour before induction of anesthesia

Oral Soluble Film:

Prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy:

Adult oral dose: 24 mg given successively as three 8 mg films 30 minutes before the start of chemotherapy.

Prevention of nausea and vomiting associated with moderately emetogenic cancer chemotherapy:

Adults and pediatric patients 12 years of age and older: One 8 mg film 30 minutes before chemotherapy followed by an 8 mg dose 8 hours later. Administer one 8 mg film twice a day (every 12 hours) for 1 to 2 days after completion of chemotherapy.
Pediatric patients 4 through 11 years of age: One 4 mg film three times a day. Administer the first dose 30 minutes before chemotherapy, with subsequent doses 4 and 8 hours later. Administer one 4 mg film three times a day (every 8 hours) for 1 to 2 days after completion of chemotherapy.
Prevention of nausea and vomiting associated with radiotherapy: The adult dosage is one 8 mg film three times a day.
Postoperative nausea and vomiting: The adult dose is 16 mg given successively as two 8 mg films 1 hour before anesthesia.

The recommended adult dosage for prevention of nausea and vomiting associated with chemotherapy or radiation therapy is 8 mg taken orally every 8 hours. For prevention of post-surgical nausea and vomiting, the recommended adult dosage is 8 mg taken orally 1 hour before the start of surgery. For opioid-induced nausea and vomiting, the recommended adult dosage is 4 mg taken orally every 8 hours.

Administration

Ondansetron is usually taken orally, but it can also be administered intravenously or intramuscularly. It is best to take the medication on an empty stomach and drink plenty of fluids. Your healthcare provider may adjust the dosage according to your individual needs.

Side Effects

Common side effects of ondansetron include dry mouth, headaches, constipation, dizziness, drowsiness, weakness, and blurred vision. More serious side effects may include an irregular or fast heartbeat, difficulty breathing, chest tightness, confusion, fainting, seizures, and worsening nausea or vomiting. If you experience any of these side effects, contact your healthcare provider right away.

Toxicity

Ondansetron is considered to be safe at the recommended therapeutic doses. However, if taken in large doses, it may cause severe side effects, such as an irregular or fast heartbeat, difficulty breathing, confusion, fainting, seizures, and worsening nausea or vomiting.

Precautions

Before taking ondansetron, tell your healthcare provider if you have any medical conditions, allergies, or if you are taking any other medications, including prescribed or over-the-counter drugs, vitamins, or herbal supplements. Be sure to tell your healthcare provider if you become pregnant or plan to become pregnant while taking ondansetron.

Interactions

Ondansetron may interact with certain drugs, such as apomorphine, certain antibiotics, certain antifungal agents, and certain drugs used to treat HIV/AIDS. Inform your healthcare provider of any medications you are taking, including prescribed and over-the-counter medications, vitamins, and herbal supplements before starting ondansetron.

Disease Interaction

Ondansetron may interact with certain diseases or medical conditions. Inform your healthcare provider of any medical conditions you have, including kidney disease, liver disease, or any heart diseases before taking ondansetron. Tell your healthcare provider if you become pregnant or plan to become pregnant while taking ondansetron.

Drug Interaction

Ondansetron may interact with certain drugs, such as apomorphine, certain antibiotics, certain antifungal agents, and certain drugs used to treat HIV/AIDS. Inform your healthcare provider of any medications or herbal supplements you are taking before starting ondansetron.

Food Interactions

There are no known food interactions with ondansetron. However, it is best to take this medication on an empty stomach with plenty of fluids. Talk to your healthcare provider for more information.

Pregnancy Use

Ondansetron is classified as a Pregnancy Category B drug, meaning it has been tested in pregnant women but it has not been established as safe to use during pregnancy. Talk to your healthcare provider if you are pregnant or plan to become pregnant while taking ondansetron.

Lactation Use

Not enough data exists to determine whether ondansetron passes into breast milk. Therefore, it is not recommended for use during lactation. Inform your healthcare provider if you are breastfeeding or plan to breastfeed while taking this medication.

Acute Overdose

Signs and symptoms of an acute overdose of ondansetron may include drowsiness, confusion, slow heartbeat, muscle weakness, difficulty breathing, confusion, and fainting. If you suspect an overdose, contact your healthcare provider or poison control hotline immediately.

Contraindication

Ondansetron should not be used in patients who have known hypersensitivity to this drug or any of its components. It should also not be used in patients with low blood pressure or who are taking certain medications used to treat HIV/AIDS.

Use Direction

Follow your healthcare provider's instructions carefully. Take ondansetron exactly as prescribed. Do not take more or less than the recommended dose and do not take for a longer period than recommended. It is important to take this medication on an empty stomach and to drink plenty of fluids.

Storage Condition

Ondansetron should be stored in a cool, dry place, away from light and moisture. Do not store in the bathroom or kitchen. Keep the medication away from children and pets.