What happens if I take ondansetron (Zofran) sublingually with water?

Taking Ondansetron Sublingually with Water

Taking ondansetron sublingually with water negates the purpose of the sublingual administration and may reduce the medication's effectiveness, as the water will likely wash the medication down the throat before it can be properly absorbed under the tongue.

Proper Administration of Sublingual Ondansetron

Ondansetron orally disintegrating tablets (ODT) are specifically designed to dissolve rapidly on the tongue without requiring water. According to the FDA drug label:

1. With dry hands, remove the tablet from the bottle or peel back the paper backing of the blister
2. IMMEDIATELY place the ondansetron orally disintegrating tablet on top of the tongue where it will dissolve in seconds
3. Swallow with saliva only
4. Administration with liquid is not necessary 1

Why Water Should Be Avoided

When taking ondansetron sublingually, water should be avoided for several reasons:

• Water can wash the medication down the throat before it has time to be absorbed under the tongue
• Preliminary observations suggest a higher incidence of headache when ondansetron ODT is taken with water compared to without water 1
• The sublingual route is specifically chosen to improve drug absorption compared to regular tablets, particularly when patients are actively vomiting 2

Potential Consequences

If you take ondansetron sublingual tablets with water, the following may occur:

1. Reduced effectiveness: The medication may not work as intended since it won't be properly absorbed sublingually
2. Delayed onset of action: The antiemetic effect may take longer to begin
3. Increased risk of side effects: Common side effects include:
   • Headache (reported in 9-27% of patients) 1
   • Dizziness (reported in 5-7% of patients) 1
   • Constipation or diarrhea (reported in 4-9% of patients) 1

Correct Usage in Specific Situations

For patients with cyclic vomiting syndrome (CVS) or other conditions requiring antiemetic therapy:

• Even when actively retching and vomiting, sublingual ondansetron may improve drug absorption compared to regular tablets 2
• The sublingual form is particularly advantageous when oral intake is difficult due to nausea and vomiting 2

Alternative Administration Options

If sublingual administration is difficult, consider these alternatives:

• Ondansetron is also available in intravenous form (8 mg or 0.15 mg/kg) for moderate to severe vomiting 2, 3
• For chemotherapy-induced nausea and vomiting, dosing varies based on the emetogenic potential of the chemotherapy regimen 2

Important Precautions

• Monitor for QT interval prolongation in patients with electrolyte abnormalities, congestive heart failure, or those taking other QT-prolonging medications 3
• In severe hepatic impairment, the total daily dose should not exceed 8 mg 1
• Rare but serious side effects can include hypersensitivity reactions and transient visual disturbances 1

For optimal effectiveness, always take sublingual ondansetron as directed by placing it on your tongue and allowing it to dissolve without water.