alosetron vs promethazine
Side-by-side comparison of alosetron and promethazine Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Lotronex
Phenergan
Alosetron (Lotronex) is a medicine for women with severe diarrhea-predominant irritable bowel syndrome (IBS). It helps to reduce diarrhea and stomach pain.
Promethazine suppositories are a medicine that can help with allergies, motion sickness, nausea, vomiting, and sleep problems. It works by blocking certain natural substances in your body.
Alosetron is used to treat severe diarrhea-predominant irritable bowel syndrome (IBS) in women. It is for women whose IBS symptoms have lasted for 6 months or longer. You should have already ruled out other possible causes of your symptoms. This medicine is only for you if other treatments have not worked well enough.
This medicine can treat allergy symptoms like a runny nose or itchy eyes. It can also help prevent motion sickness. Promethazine can also be used to control nausea and vomiting, especially after surgery. Sometimes, it's used to help you relax or sleep before or after surgery.
Alosetron blocks a substance called serotonin in your gut. Serotonin can speed up bowel movements. By blocking serotonin, alosetron slows down your bowel and reduces diarrhea.
Promethazine belongs to a class of drugs called antihistamines and antiemetics. It works by blocking histamine, a substance in the body that causes allergic symptoms. It also affects the part of the brain that controls nausea and vomiting.
- • Constipation
- • Abdominal discomfort and pain
- • Nausea
- • Gastrointestinal discomfort and pain
- • Drowsiness
- • Dry mouth
- • Blurred vision
- • Dizziness
- Medicine not working 11
- Diarrhea 10
- Feeling sick to your stomach 8
- Using the medicine for something it's not approved for 7
- Stomach pain 6
- Feeling sick to your stomach 2,534
- Throwing up 1,736
- Aches or soreness 1,457
- Feeling very tired 1,408
- Loose or watery stools 1,272
Alosetron can cause serious gut problems, like ischemic colitis (reduced blood flow to the bowel) and severe constipation. These problems can lead to hospitalization, surgery, or even death. Stop taking alosetron right away if you get constipated or have symptoms of ischemic colitis, like bloody diarrhea or bad stomach pain. Call your doctor immediately.
Promethazine suppositories should not be used in children under 2 years old because it can cause serious breathing problems, which can be fatal. Use with caution in children 2 years and older, and use the lowest effective dose. Avoid giving this medicine with other drugs that can also cause breathing problems.
It is not known if alosetron can harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is also not known if alosetron passes into breast milk. Talk to your doctor about the best way to feed your baby if you take alosetron.
Tell your doctor if you are pregnant or breastfeeding before using this medicine. It is not known if promethazine can harm an unborn baby or pass into breast milk.
How to Read This alosetron vs promethazine Comparison
alosetron is classified in the 5-HT3 Antagonist (IBS-D) drug class, while promethazine sits within the Phenothiazine Antiemetic / Antihistamine class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, alosetron has 42 submissions while promethazine has 8,407. Those figures reflect cumulative reporting volume — not per-patient risk — so older, widely dispensed drugs typically look worse on count alone. No direct interaction between these two drugs is listed in our FDA-derived dataset, though co-prescription still warrants pharmacist review. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between alosetron and promethazine — always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.