Onset

Brand name:

Onset

Generic name:

Ondansetron HCL

Available dosage forms and their doses.

Tablets: 4mg/8mg

Injections: 4mg/8mg transparent glass ampoule.

Therapeutic class:

Anti-emetic

Pharmacologocal class:

Serotonin 5HT3 receptor antagonist

Manufacturer:

Pharmacy Laboratories (Pvt limited)

Storage:

Injection: store between 2-30 degree Celsius

Tablets: Room temperature.(15-25 degree Celsius)

Prescription drug?

Yes

Clinical pharmacology (Mechanism of action):

Ondansetron selectivity blocks the serotonin receptor sub-type 5HT3 located on vagal afferents. These receptors are usually stimulated by the 5HT serotonin hormone secreted from enterochromaffin cells of the small intestine.

Indications and dosages:

• Chemotherapy-induced nausea and vomiting:

  
  

Adults:

8mg I.V. infused over 15 min; 30 min before chemo.

 Max dose: 32 mg / 24 hrs

 After 24hrs of chemo, 8 mg orally every 8 hrs for up to 5 days.

Children:

4-12 yrs of age; 3-5mg/m2 over 15min immediately before chemo. After chemo, 4 mg tab every 8 hrs for up to 5 days.

Geriatrics:

It's the same dose as for adults.

• Radiotherapy-induced nausea and vomiting:

  
  

Adults :

 8mg tab 1-2 hrs before therapy.

Geriatrics:

It's the same dose as for adults.

• Post-operative nausea and vomiting:

Adults:

16 mg orally 1 hr before anesthesia.

Side Effects:

Common:

• Headache

• Tiredness

• Constipation/diarrhea

Serious

•  Severe allergic reactions

• QT prolongation

• Torsade de pointes

• Myocardial infarction

• Serotonin syndrome

Interactions:

• With drugs that cause QT prolongation

• With SSRIs

• With SNRIs

• With sumatriptan (anti-migraine drug)

• With apomorphine (anti-parkinsonian drug)

• Tramadol (opioid analgesic)

  
  

Pregnancy:

Not acceptable but if treatment is necessary and outweighs the risk, then it can be given to pregnant women.

Lactating mothers:

Not acceptable.

Precautions:

• Ondansetron is not for motion-sickness-induced vomiting.

• Patients with hepatic impairment/jaundice should avoid this medicine.

Counselling point

Onset can be taken with or without food but greater effect is seen when taken on an empty stomach or 1 hr before taking food or 2 hrs after taking food.