Compare Zofran vs. Phenergan

Head-to-head comparisons of medication uses, side effects, ratings, and more.



Helps you feel less queasy. Zofran (Ondansetron) works well to prevent nausea and vomiting, and it's available in different forms that you don't have to swallow.Helps you feel less queasy. Phenergan (Promethazine) is used to treat and prevent nausea and vomiting from surgery, motion sickness, or pregnancy. While it's cheap and available in different forms to make it easier to take, it can make you feel very sleepy, and its side effects mean that children under 2 and adults over 65 shouldn't take it.
Find lowest prices
Powered by GoodRxSave on your next prescription. Be sure you’re getting the lowest price for your medication, even if you have insurance.
Reviews & ratings
Filter group. All currently selected
Filter group. All currently selected
Reviews for Zofran (Ondansetron)
of people say Zofran (Ondansetron) is worth it
say it works well
say it's a big hassle
355 reviews
Reviews for Phenergan (Promethazine)
+13% vs. Zofran (Ondansetron)
+23% vs. Zofran (Ondansetron)
+12% vs. Zofran (Ondansetron)
Side effects
  • Fever 5%
  • Drowsiness 4%
  • Headache 2%
More Zofran side effects »

The Phenergan FDA package insert doesn’t have numbers about how common side effects are.

More about Phenergan side effects »
How it works
Zofran (Ondansetron) is an antiemetic (anti-nausea medicine). It works by blocking the nerves that cause your nausea and vomiting reflex.Phenergan (Promethazine) is an antihistamine, which helps control allergies. It also seems to block your body's natural reflex for vomiting, which makes it useful as an antiemetic (anti-nausea medicine).
Type of medication
Selective 5-HT3 antagonist
Prescription only
Prescription only
Available as
  • Pill
  • Dissolving tablet
  • Liquid
  • Sublingual film
  • Pill
  • Liquid
  • Suppository
Used for (click to learn more)
Risk factors for serious side effects
    • Long QT syndrome
    Detailed Zofran (Ondansetron) risks & warnings »
    • Children under 2 years of age
    • History of seizures
      • Age over 65
        Detailed Phenergan (Promethazine) risks & warnings »
        Pregnancy category
        BFDA pregnancy category (Probably safe)

        Research studies with animals haven’t found a risk to unborn babies, but it hasn’t been properly studied in humans.

        See the FDA package insert
        CFDA pregnancy category (Weigh risks vs. benefits)

        Research studies with animals found harmful effects on unborn babies. It hasn’t been properly studied in humans. The benefits might outweigh the risks even if you’re pregnant. Talk with your doctor.

        See the FDA package insert
        No specific alcohol-related info.
        • Can make you feel very sleepy, especially if you're taking other drugs that can make you sleepy or if you drink alcohol.
        • Don't drink alcohol to avoid intense side effects.
        No specific food-related info.No specific food-related info.
        Kidneys and liver
        No specific kidneys and liver-related info.No specific kidneys and liver-related info.
        No specific sex-related info.No specific sex-related info.
        No specific sleep-related info.No specific sleep-related info.
        No specific weight-related info.No specific weight-related info.
        Upsides and benefits
        • Available in forms that you don't have to swallow (like a tablet or film that dissolves in your mouth) if you're having trouble keeping anything down.
        • Starts working fast (in 30 minutes.
        • Available in generic.
        • Available as a syrup or tablet that you can take by mouth, or as a rectal suppository if you're unable to take anything by mouth.
        • Available in generic.
        Downsides and risks
        • Can cause headaches.
        • Can interact with antidepressants.
        • Can only be used to prevent nausea and vomiting, not to treat if it's already happening.
        • Can make you feel very sleepy, especially if you're taking other drugs that can make you sleepy or if you drink alcohol.
        • Can't be used in children under 2 years of age or if you're over 65 because of increased risk from side effects.
        • Can make your skin more sensitive to the sun.
        Tips from our pharmacists for people taking the medication
        • If you're using the disintegrating tablet, make sure your hands are dry first, peel off the foil and remove the tablet. Place the tablet on the tongue to let it dissolve naturally, then swallow. Don't drink water or anything else.
        • Can cause headache, fatigue or constipation.
        • If you're taking the oral film, don't chew or swallow it. Let it dissolve naturally on the tongue.
        • It takes 30 minutes for Zofran to start working.
        • Promethazine comes in different forms. Be clear on which one you were prescribed - swallow tablets orally, unwrap and insert suppositories rectally.
        • Don't give to kids 2 and under.
        • You'll likely feel very sleepy, sluggish, or less alert after taking Promethazine. Avoid driving or other tasks that require your focused attention; be safe.
        • Don't drink alcohol to avoid intense side effects.
        • Taking certain medications for pain, allergies, or mood conditions can worsen the side effects of Promethazine.
        • Avoid using if you experience seizures (epilepsy).
        • Don't use if you're 65 or older because you're at higher risk for serious side effects.
        Learn more
        More about ZofranSide effectsReviews & ratingsAlternativesFDA package insert
        More about PhenerganSide effectsReviews & ratingsAlternativesFDA package insert