Onset Side Effects

Onset is a medication commonly used to prevent and treat nausea and vomiting, particularly associated with chemotherapy, radiation therapy, surgery, and certain medical conditions. While it is generally well-tolerated, like all medications, it can cause side effects. Common and less common side effects of Onset may include:

Common Side Effects

• Headache
• Constipation
• Diarrhea
• Fatigue
• Dizziness
• Lightheadedness
• Unpleasant taste in the mouth
• Mild allergic reactions such as skin rash or itching

Less Common Side Effects

• Irregular heartbeats (arrhythmias): Onset may affect the electrical activity of the heart, leading to irregular heart rhythms. This is more likely to occur in people with a history of heart problems.
• QT interval prolongation: Prolongation of the QT interval on the electrocardiogram (ECG) is a less common but more serious side effect. It can increase the risk of a potentially life-threatening arrhythmia known as Torsades de Pointes.
• Serotonin syndrome: Although rare, Onset may contribute to serotonin syndrome when used in combination with other medications that affect serotonin levels, such as selective serotonin reuptake inhibitors (SSRIs). Symptoms of serotonin syndrome include agitation, hallucinations, rapid heartbeat, fever, muscle stiffness, and tremors.
• Allergic reactions: Severe allergic reactions to Onset are rare but can occur. Symptoms may include swelling of the face, lips, tongue, or throat; difficulty breathing; and hives.
• Blurred vision: Some individuals may experience visual disturbances while taking Onset.
• Liver problems: Rarely, Onset can affect liver function and lead to elevated liver enzymes.

Onset is one of the leading brands of Ondansetron, manufactured and marketed by Pharmedic Laboratories Pakistan.

Presently, Onset is available in Tablet and Injectable Forms

Onset Tablets : 8mg Strength

Onset Injections : 4mg and 8mg

1. Serotonergic Medications: Onset can enhance the serotonergic effects of other medications, increasing the risk of serotonin syndrome. This is particularly important if you are taking selective serotonin reuptake inhibitors (SSRIs) or other serotonergic antidepressants.
2. Apomorphine: The concurrent use of Onset and apomorphine (used to treat Parkinson’s disease) can lead to a significant drop in blood pressure and a risk of profound hypotension.
3. Drugs Prolonging the QT Interval: Onset itself can prolong the QT interval on the electrocardiogram (ECG), and its risk increases when used with other drugs that also prolong the QT interval. This can potentially lead to a dangerous arrhythmia called Torsades de Pointes. Be cautious when taking Onset with medications like certain antiarrhythmics, antipsychotics, and certain antibiotics.
4. Tramadol: There is a risk of serotonin syndrome when Onset is used in combination with tramadol, a centrally-acting analgesic. Both medications affect serotonin levels, and the combination can be problematic.
5. Anticonvulsants: Onset may reduce the effectiveness of anticonvulsant medications like carbamazepine, phenytoin, and phenobarbital.
6. CYP3A4 and CYP1A2 Inhibitors/Inducers: Onset is metabolized in the liver by cytochrome P450 enzymes, particularly CYP3A4 and CYP1A2. Medications that inhibit or induce these enzymes may affect the blood levels of Onset.
7. Rifampin: Rifampin, an antibiotic used to treat tuberculosis, is a strong inducer of CYP1A2 and can significantly reduce the effectiveness of Onset.
8. Other Medications: There may be additional interactions with specific medications, so it’s essential to inform your healthcare provider of all the drugs, supplements, and herbal products you are taking.