famciclovir vs promethazine
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Side-by-side comparison of famciclovir and promethazine. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
minor Known Drug Interaction
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.
Famvir
Phenergan
Famciclovir is an antiviral medicine. It helps to treat infections caused by certain viruses.
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.
This medicine treats herpes infections. It can treat cold sores, genital herpes, and shingles. It can also prevent genital herpes outbreaks. This medicine may not work for everyone, including first-time genital herpes, eye shingles, or certain immunocompromised patients.
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.
Famciclovir stops the virus from multiplying. It does this by blocking a key enzyme the virus needs to make copies of itself. This helps your body fight off the infection.
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.
- • Headache
- • Nausea
- • Drowsiness
- • Dry mouth
- • Blurred vision
- • Dizziness
- Fatigue 185
- Diarrhoea 179
- Nausea 145
- Headache 135
- Pain 118
- Nausea 2,530
- Vomiting 1,734
- Pain 1,453
- Fatigue 1,408
- Diarrhoea 1,271
If you have kidney problems, make sure your doctor knows. Taking too much famciclovir when you have kidney problems can damage your kidneys.
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.
Tell your doctor if you are pregnant or plan to become pregnant. Untreated herpes during pregnancy can harm the baby. It is not known if famciclovir passes into breast milk.
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.
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How to Read This famciclovir vs promethazine Comparison
famciclovir is classified in the Antiviral (Nucleoside Analog) 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, famciclovir has 762 submissions while promethazine has 8,396. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to promethazine does not significantly affect how famciclovir is processed or activated by the body.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot represent individual circumstances. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This registry does not provide medical, treatment, substitution, or medication-change directions for famciclovir or promethazine.
Registry boundary: This comparison displays source-record fields and does not provide individualized medical direction.