{"ok":true,"entry":{"slug":"valaciclovir","kind":"medication","name":"valaciclovir","aliases":["valacyclovir","Valtrex"],"brands_sg":["Valtrex","Valovir","Vaciclor"],"class":"antiviral","tags":["other"],"use_for":"prescribed for shingles, cold sores and genital herpes","use_after":"fda: tablets may be given without regard to meals","use_duration":null,"take_with":"water · healthhub: regular water intake matters on it","pros":["fda: the cold sore course is one day, two doses","fda: no known clinically significant interactions","healthhub: taken with or without food"],"cons":["healthhub: kidney problems, confusion, hallucinations","healthhub: headache, nausea and rash are common","healthhub: sun-exposed skin can react"],"dose_note":"the us fda label for valacyclovir tablets gives adult regimens by indication: cold sores '2 grams every 12 hours for 1 day', initial genital herpes 1 gram twice daily for 10 days, recurrent episodes 500 mg twice daily for 3 days, suppression 1 gram once daily, and herpes zoster '1 gram 3 times daily for 7 days'. 2 g every 12 hours — 4 g in one day — is the highest daily figure the label carries, and it applies to a single day of cold-sore treatment only; herpes zoster's 3 g a day is the highest figure for a multi-day course. for chickenpox in children the same label caps dosing at 'not to exceed 1 gram 3 times daily'. singapore registers only the 500 mg tablet, so the label's gram-level doses correspond to several tablets per dose. in singapore the prescriber sets the dose.","dosage":null,"ul_status":null,"sg_class":"prescription-only","cautions":["healthhub: dizziness — driving and machinery affected","fda: contraindicated after hypersensitivity to aciclovir","healthhub: confusion, hallucinations or unsteady walking","healthhub: reduced urine or blood in urine — a kidney sign"],"clashes":[{"src":["hh_val_food"],"note":"healthhub: this medication may reduce the effects of certain vaccines and should be avoided; no vaccine is named","with":"certain vaccines"},{"src":["hh_val_food","fda_val_di"],"note":"healthhub: may increase the risk of kidney-related side effects; the fda label states no clinically significant interactions are known","with":"other medicines affecting the kidneys"}],"sources":[{"id":"hsa_register","url":"https://data.gov.sg/datasets/d_767279312753558cbf19d48344577084/view","label":"HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, cached in full and filtered locally)","quote":"Only 3 valaciclovir rows exist, all 'Prescription Only' and all 500 mg tablets — SIN08229P VALTREX TABLET 500 mg, SIN14878P VALOVIR 500, SIN14207P Vaciclor Tablet 500 mg; ATC J05AB11.","accessed":"2026-08-27"},{"id":"hh_val_uses","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub (Pharmaceutical Society of Singapore) — Valaciclovir: what is this medication for","quote":"This medication is also known as 'valacyclovir'. It is an antiviral medication used to treat shingles, susceptible viral infections of the skin and genitals, cold sores, prevent viral infections after organ transplants, treat and prevent viral infections of the eye.","accessed":"2026-08-27"},{"id":"hh_val_howto","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub — Valaciclovir: how should I take this medication","quote":"You may take this medication with or without food. Swallow the tablets whole with a drink of water. It is very important that you drink water regularly while you are taking the medication.","accessed":"2026-08-27"},{"id":"hh_val_prec","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub — Valaciclovir: what precautions should I take","quote":"You are allergic to this medication or any of the other ingredients … Do not drive, use machinery or do anything else that could be dangerous if you are dizzy or are not alert.","accessed":"2026-08-27"},{"id":"hh_val_se","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub — Valaciclovir: common side effects","quote":"Headache; Rash, skin itchiness; Nausea, vomiting, diarrhoea, abdominal pain; Skin reaction after exposure to sunlight; Feeling unwell; Dizziness","accessed":"2026-08-27"},{"id":"hh_val_rare","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub — Valaciclovir: rare but serious side effects","quote":"Kidney problem: Unable to pass urine, change in urine volume, blood in urine; Feeling confused, change in behaviour, mood changes; Seeing or hearing things that are not present; Slow, slurred speech; Seizures, tremors; Unsteadiness when walking","accessed":"2026-08-27"},{"id":"hh_val_food","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/valaciclovir","label":"HealthHub — Valaciclovir: what food or medication should I avoid","quote":"This medication may reduce the effects of certain vaccines and should be avoided. Other medications may increase the risks of this medication's kidney-related side effects. You should therefore avoid taking these medications together.","accessed":"2026-08-27"},{"id":"fda_val_dose","url":"https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22valacyclovir%22&limit=5","label":"US FDA label — valacyclovir tablets, section 2 Dosage and Administration (adult), via openFDA drug/label.json","quote":"Valacyclovir tablets may be given without regard to meals … Cold Sores 2 grams every 12 hours for 1 day … Herpes Zoster 1 gram 3 times daily for 7 days","accessed":"2026-08-27"},{"id":"fda_val_dose_gh","url":"https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22valacyclovir%22&limit=5","label":"US FDA label — valacyclovir tablets, section 2.1 genital herpes regimens, via openFDA drug/label.json","quote":"Genital Herpes Initial episode 1 gram twice daily for 10 days; Recurrent episodes 500 mg twice daily for 3 days; Suppressive therapy Immunocompetent patients 1 gram once daily","accessed":"2026-08-27"},{"id":"fda_val_dose_ped","url":"https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22valacyclovir%22&limit=5","label":"US FDA label — valacyclovir tablets, section 2.2 Pediatric Dosage, via openFDA drug/label.json","quote":"Chickenpox (aged 2 to less than 18 years) 20 mg/kg 3 times daily for 5 days; not to exceed 1 gram 3 times daily","accessed":"2026-08-27"},{"id":"fda_val_ci","url":"https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22valacyclovir%22&limit=5","label":"US FDA label — valacyclovir tablets, section 4 Contraindications, via openFDA drug/label.json","quote":"Valacyclovir tablets are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to valacyclovir, acyclovir, or any component of the formulation","accessed":"2026-08-27"},{"id":"fda_val_di","url":"https://api.fda.gov/drug/label.json?search=openfda.generic_name:%22valacyclovir%22&limit=5","label":"US FDA label — valacyclovir tablets, section 7 Drug Interactions, via openFDA drug/label.json","quote":"No clinically significant drug-drug or drug-food interactions with valacyclovir tablets are known.","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:33.302383+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}