promethazine
Brand names: Phenergan
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.
Drug Shortage Alert
promethazine is currently listed as in shortage by the FDA. Affected manufacturer: Hikma Pharmaceuticals USA, Inc.. Status: Available.
View all drug shortages →Drug Pricing (NADAC)
Generic Price
$2.24/unit
Generic Available
Yes (26 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine can treat allergy symptoms like a runny nose or itchy eyes.
Common side effects
Drowsiness, Dry mouth, Blurred vision
Key warnings
Promethazine suppositories should not be used in children under 2 years old because it can cause serious breathing problems, which can be fatal.
How It Works
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.
How to Take It
This medicine comes as a suppository that you insert into your rectum. For allergies, you might use it before bed, or several times a day. For motion sickness, take it 30-60 minutes before traveling, and again 8-12 hours later if needed. Follow your doctor's instructions on how often to use it.
Pregnancy & Breastfeeding
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.
Missed Dose
If you miss a dose, use it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store the suppositories in the refrigerator between 36°F and 46°F (2°C and 8°C) in a tightly closed container.
Side Effects (from patient reports)
Based on 13,190 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 17,969 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 1996–2025.
Total Reports
17,969
Death-Related Reports
1,754
Hospitalization Reports
7,143
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | NAUSEA | 2,530 |
| 2 | VOMITING | 1,734 |
| 3 | PAIN | 1,453 |
| 4 | FATIGUE | 1,408 |
| 5 | DIARRHOEA | 1,271 |
| 6 | HEADACHE | 1,191 |
| 7 | DYSPNOEA | 1,063 |
| 8 | ANXIETY | 864 |
| 9 | DRUG INEFFECTIVE | 855 |
| 10 | ASTHENIA | 804 |
| 11 | PNEUMONIA | 791 |
| 12 | ABDOMINAL PAIN | 776 |
| 13 | PYREXIA | 768 |
| 14 | DIZZINESS | 752 |
| 15 | MALAISE | 733 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
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.
Known Drug Interactions
Epinephrine - Because of the potential for promethazine HCl to reverse epinephrine's vasopressor effect, epinephrine should NOT be used to treat hypotension associated with Promethazine HCl Suppositories overdose.
Mechanism: Promethazine can block the way epinephrine normally raises blood pressure, which might cause blood pressure to drop even lower.
What to do: Do not use epinephrine to treat low blood pressure if a person has taken too much promethazine.
7.2 Potential for Other Drugs to Affect Penciclovir No clinically significant alterations in penciclovir pharmacokinetics were observed following single-dose administration of 500 mg famciclovir after pretreatment with multiple doses of allopurinol, cimetidine, theophylline, zidovudine, promethazine, when given shortly after an antacid (magnesium and aluminum hydroxide), or concomitantly with emtricitabine. Clinical interaction studies of famciclovir with cimetidine and promethazine, in vitro inhibitors of aldehyde oxidase, did not show relevant effects on the formation of penciclovir.
Mechanism: Promethazine does not significantly affect how famciclovir is processed or activated by the body.
What to do: These medicines can be taken together safely as prescribed by your doctor.
Promethazine: Coadministration of a single dose of zaleplon and promethazine (10 and 25 mg, respectively) resulted in a 15% decrease in maximal plasma concentrations of zaleplon, but no change in the area under the plasma concentration-time curve. However, the pharmacodynamics of coadministration of zaleplon and promethazine have not been evaluated.
Mechanism: Promethazine slightly reduces the highest level of zaleplon in your blood, but the total amount in your body remains about the same.
What to do: Be careful when combining these drugs, as doctors are not yet sure how they might affect your coordination or sleepiness when used together.
Common Questions
Can I use this for my baby's cold?
Will this medicine make me sleepy?
Can I drink alcohol while using this?
How long does it take for this medicine to work?
What should I do if I feel dizzy?
Can I drive after using this medicine?
Can I use this for asthma?
What if I have an allergic reaction?
Can I use this with other medicines?
How often can I use this medicine?
What are the common side effects of promethazine?
Does promethazine interact with other medications?
What drug class is promethazine?
Is promethazine safe during pregnancy?
Is promethazine currently in shortage?
Related Medications in Phenothiazine Antiemetic / Antihistamine
Other drugs grouped near promethazine — same-class peers and common alternatives.
alosetron
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aprepitant
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bisacodyl
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bismuth subsalicylate
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cimetidine
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What the FDA Data Shows for promethazine
The FDA label for promethazine (sold under brand names such as Phenergan) classifies it as a prescription-only medication in the Phenothiazine Antiemetic / Antihistamine class. This medicine can treat allergy symptoms like a runny nose or itchy eyes. Official labeling lists 4 commonly reported side effects, including Drowsiness, Dry mouth, Blurred vision.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 13,190 voluntary reports. The database also lists 3 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $2.24.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: June 30, 2023
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages