Ondansetron 4mg Tablets

Ondansetron is a selective serotonin 5-hydroxytryptamine3 (5-HT3) receptor antagonist. Chemotherapeutic agents and radiation therapy cause release of serotonin from enterochromaffin cells of the small intestine, which then stimulates 5-HT3 receptors located on vagal afferent nerves to initiate the vomiting reflex. Ondansetron blocks the serotonin stimulation of 5-HT3 receptors in the periphery (on vagal nerve terminals) and centrally (in the chemoreceptor trigger zone, CTZ).

Urgent Side Effects: Seek Medical Help Right Away

Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Trouble passing urine
Dizziness
Sudden chest pain or tightness
Abnormal heartbeat, including a fast or irregular heartbeat, or fainting (this medication can cause a prolonged QT interval, which may lead to a potentially life-threatening abnormal heartbeat called torsades de pointes)
Serotonin syndrome, a severe and potentially life-threatening condition, which may be more likely to occur if you are taking certain other medications. Symptoms include:
+ Agitation
+ Change in balance
+ Confusion
+ Hallucinations
+ Fever
+ Fast or abnormal heartbeat
+ Flushing
+ Muscle twitching or stiffness
+ Seizures
+ Shivering or shaking
+ Excessive sweating
+ Severe diarrhea
+ Upset stomach or vomiting
+ Severe headache
Stomach pain or swelling of the stomach area, especially if you have had surgery in the stomach area or have experienced nausea and vomiting after chemotherapy (this medication may mask the symptoms of a bowel block)

Other Possible Side Effects

Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it is essential to contact your doctor or seek medical help if you notice any of the following:

Headache
Feeling tired or weak
Diarrhea or constipation
Feeling sleepy
Anxiety

This is not an exhaustive list of possible side effects. If you have concerns or questions about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you have a prolonged QT interval visible on an electrocardiogram (ECG).
* If you are currently taking apomorphine.

This list is not exhaustive, and it is crucial to disclose all your medications, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins, as well as any health problems you may have. Your doctor and pharmacist need this information to ensure safe treatment. Do not initiate, discontinue, or modify the dosage of any medication without first consulting your doctor to confirm that it is safe to do so in conjunction with this medication.

It is essential to inform all of your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you are pregnant, planning to become pregnant, or are currently breast-feeding, be sure to discuss this with your doctor. Your doctor will need to weigh the benefits and risks of this medication for both you and your baby to determine the best course of action.

• Apomorphine (concurrent use with ondansetron is contraindicated due to risk of profound hypotension and loss of consciousness).

• QT-prolonging drugs (e.g., amiodarone, sotalol, quinidine, procainamide, disopyramide, dofetilide, dronedarone, antipsychotics like thioridazine, ziprasidone, macrolide antibiotics like erythromycin, fluoroquinolone antibiotics like moxifloxacin, tricyclic antidepressants). Concomitant use increases risk of Torsades de Pointes.
• Serotonergic drugs (e.g., SSRIs, SNRIs, MAOIs, tricyclic antidepressants, fentanyl, tramadol, lithium, triptans, St. John's Wort) - increased risk of serotonin syndrome.

• CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin) - may decrease ondansetron plasma concentrations, potentially reducing efficacy.
• Tramadol - increased risk of serotonin syndrome.

• Not many clinically significant minor interactions reported.

• Symptoms of QT prolongation/arrhythmia: Dizziness, lightheadedness, syncope, palpitations, chest pain, shortness of breath.
• Symptoms of Serotonin Syndrome: Agitation, hallucinations, delirium, coma, tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia, tremor, rigidity, myoclonus, hyperreflexia, incoordination, gastrointestinal symptoms (nausea, vomiting, diarrhea).
• Hypersensitivity reactions: Rash, urticaria, bronchospasm, angioedema, anaphylaxis.

Ondansetron is generally considered low risk during pregnancy. Observational studies have not identified a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. Use only if clearly needed.

Ondansetron is excreted into breast milk in small amounts. Limited human data suggest low risk to the infant, but potential for adverse effects like diarrhea or constipation. Use with caution; monitor infant for side effects.

Dosing varies significantly by age, weight, and indication. Safety and efficacy not established in infants younger than 1 month. Close monitoring for side effects is crucial.

No dosage adjustment is generally needed based on age alone. However, elderly patients may have prolonged half-life and reduced clearance, and may be at higher risk for QT prolongation. Monitor ECG and electrolytes, especially if co-morbidities or concomitant medications increase risk.

• Ondansetron is highly effective for chemotherapy-induced, radiation-induced, and postoperative nausea and vomiting.
• The orally disintegrating tablet (ODT) formulation is useful for patients who have difficulty swallowing or are actively vomiting.
• Be mindful of the risk of QT prolongation, especially in patients with underlying cardiac conditions, electrolyte imbalances, or those on other QT-prolonging drugs. Correct hypokalemia and hypomagnesemia before administration.
• Serotonin syndrome is a rare but serious risk, particularly when co-administered with other serotonergic agents (e.g., SSRIs, tramadol).
• Constipation is a common side effect; advise patients on appropriate bowel management.

• Granisetron (Kytril, Sancuso)
• Palonosetron (Aloxi)
• Dolasetron (Anzemet)
• Dexamethasone (often used in combination with 5-HT3 antagonists for CINV)
• Neurokinin-1 (NK1) receptor antagonists (e.g., aprepitant, fosaprepitant, netupitant, rolapitant) - often used in combination for highly emetogenic chemotherapy.
• Dopamine receptor antagonists (e.g., prochlorperazine, metoclopramide) - for less severe nausea/vomiting or as adjuncts.

If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.