{"ok":true,"entry":{"slug":"cetirizine","kind":"medication","name":"cetirizine","aliases":["cetirizine hydrochloride","cetirizine dihydrochloride","cetirizine 2hcl"],"brands_sg":["Zyrtec","Zyrtec-R","Simtec","Allertec","Adezio"],"class":"antihistamine","tags":["allergy"],"use_for":"runny nose, sneezing, itchy eyes/nose/throat, itchy rash","use_after":"once daily per label · as needed for symptoms (healthhub)","use_duration":null,"take_with":"with or without food · with water · food may slow onset","pros":["once-a-day dose — label max one 10 mg tablet in 24 h","zyrtec-r is general sale list — sold beyond pharmacies","nhs: unlikely to harm if taken long term"],"cons":["sleepy/tired in more than 1 in 10 people (nhs)","'non-drowsy' but driving care still advised","dry mouth, headache; alcohol adds to drowsiness"],"dose_note":"label: adults and children 6 years and over one 10 mg tablet once daily — 'do not take more than one 10 mg tablet in 24 hours'; zyrtec-r label: half a tablet may be used as a starting dose; 65 and over, or liver or kidney disease: label says ask a doctor; as directed on the label or by your pharmacist","dosage":null,"ul_status":null,"sg_class":"pharmacy-only","cautions":["kidney or liver problems — label says ask a doctor first; severe kidney disease (egfr below 15): zyrtec-r label says do not use","epilepsy or seizures, enlarged prostate or difficulty urinating — ask a pharmacist first","pregnant: label says ask a health professional first · breastfeeding: us label says not recommended; sg zyrtec-r label says don't take","drowsy? label: care when driving or operating machinery · allergy test due: nhs says cetirizine may affect the results"],"clashes":[{"src":["fda_zyrtec_otc","healthhub_cet"],"food":true,"note":"label: avoid alcoholic drinks — alcohol, sedatives, and tranquilizers may increase drowsiness","with":"alcohol"},{"src":["fda_zyrtec_otc","fda_zyrtec_rx"],"note":"label: ask a doctor or pharmacist before use if taking tranquilizers or sedatives; fda rx label: concurrent use should be avoided","with":"sedatives, tranquilizers, sleeping tablets (cns depressants)"},{"src":["healthhub_cet","ndf_zyrtec_r_tab"],"note":"healthhub: check with your healthcare professional before taking two otc medicines together to prevent overdosing; sg zyrtec-r label: don't take if you use other anti-allergy medicines","with":"other antihistamines (incl. otc cold and allergy combos)"},{"src":["nhs_cet_interact"],"note":"nhs: check with your pharmacist or doctor first; same caution for herbal remedies with those effects","with":"any medicine that causes drowsiness, dry mouth or difficulty peeing"},{"src":["fda_zyrtec_rx"],"note":"fda rx label: small decrease in cetirizine clearance; no clinically significant interaction found with low-dose theophylline, azithromycin, pseudoephedrine, ketoconazole or erythromycin","with":"theophylline (400 mg)"}],"sources":[{"id":"ndf_zyrtec_r_tab","url":"https://www.ndf.gov.sg/about-drugs/product-information/sin14890p/","label":"MOH National Drug Formulary — ZYRTEC-R FILM-COATED TABLET 10 MG [SIN14890P] (HSA-registered product record + clinical info)","quote":"CETIRIZINE 2HCL - 10 MG … TABLET, FILM COATED … GENERAL SALE LIST … GLAXOSMITHKLINE PTE LTD … 1 tablet once daily … Half of the tablet as a starting dose may be used if this leads to satisfactory control … Do not take more than one 10 mg tablet in 24 hours … Don't take Zyrtec-R: … If you have severe kidney disease (severe impairment of kidney function with estimated GFR less than 15 ml/min). If you use other anti-allergy medicines. If you are breastfeeding … If you think any of these applies to you, don't take Zyrtec-R until you have checked with your doctor or pharmacist","accessed":"2026-08-27"},{"id":"ndf_zyrtec_tab","url":"https://www.ndf.gov.sg/about-drugs/product-information/sin03022p/","label":"MOH National Drug Formulary — ZYRTEC TABLET 10 MG [SIN03022P] (HSA-registered product record)","quote":"CETIRIZINE 2HCL - 10 MG … TABLET, FILM COATED … PHARMACY ONLY MEDICINES … GLAXOSMITHKLINE PTE LTD … nasal and ocular symptoms of seasonal and perennial allergic rhinitis … symptoms of chronic idiopathic urticaria … 10 mg once daily [1 tablet, 20 drops, or 10 ml oral solution] … Hypersensitivity to any of the constituents of the formulation, to hydroxyzine or to any piperazine derivatives","accessed":"2026-08-27"},{"id":"ndf_simtec_otc","url":"https://www.ndf.gov.sg/about-drugs/product-information/sin15142p/","label":"MOH National Drug Formulary — SIMTEC TABLET 10MG (OTC) [SIN15142P]","quote":"CETIRIZINE HCL - 10 MG … TABLET, FILM COATED … GENERAL SALE LIST … DUOPHARMA (SINGAPORE) PTE LTD","accessed":"2026-08-27"},{"id":"hsa_reclass","url":"https://www.hsa.gov.sg/therapeutic-products/registration-of-therapeutic-products/variation-application/reclassification/list-of-reclassified-medicines/","label":"HSA — List of reclassified medicines (forensic class definitions: POM / P / GSL)","quote":"GSL: A therapeutic product that can be obtained from any retailer … P: A therapeutic product that can be obtained from a pharmacist at a retail pharmacy without a prescription","accessed":"2026-08-27"},{"id":"healthhub_cet","url":"https://www.healthhub.sg/medication-devices-and-treatment/medications/cetirizine","label":"HealthHub (MOH Singapore) — Cetirizine medication page (updated 3 Jun 2026)","quote":"Cetirizine belongs to a group of medicines known as antihistamines … Runny nose (due to a cold, flu or allergies) … Itch in the eyes, nose or skin … with or without food. However, food may slow down the absorption leading to a slower time to take effect … when necessary to relieve your symptoms … Liver or kidney problems … Seizures … Enlarged prostate gland … Difficulty urinating … Affect alertness (drowsiness and tiredness) … Headache … Dry mouth, skin and eyes … Avoid driving, operating machinery or other activities which require concentration while on this medication … Taking this medication with alcohol may worsen the drowsy side effect. Avoid alcohol while on this medication … Zyrtec, Adezio, Agelmin, Allercet, Allertec, Alzytec, Atrizin, Ceritec, Sunizine, and Terizin","accessed":"2026-08-27"},{"id":"nhs_cet_how","url":"https://www.nhs.uk/medicines/cetirizine/how-and-when-to-take-cetirizine/","label":"NHS — How and when to take cetirizine (reviewed 18 Feb 2025)","quote":"The usual dose for adults and children aged 12 years old and over is 10mg once a day … You can take cetirizine with or without food, but always take the tablets with a drink of water, milk or squash … Cetirizine is generally very safe. Taking an extra dose is unlikely to harm you or your child","accessed":"2026-08-27"},{"id":"nhs_cet_who","url":"https://www.nhs.uk/medicines/cetirizine/who-can-and-cannot-take-cetirizine/","label":"NHS — Who can and cannot take cetirizine (reviewed 18 Feb 2025)","quote":"have kidney failure … have epilepsy or another health problem that means you're at risk of having seizures or fits … have a condition that means you have difficulty peeing … are due to have an allergy test – taking cetirizine may affect the results","accessed":"2026-08-27"},{"id":"nhs_cet_se","url":"https://www.nhs.uk/medicines/cetirizine/side-effects-of-cetirizine/","label":"NHS — Side effects of cetirizine (reviewed 18 Feb 2025)","quote":"feeling sleepy and tired. This happens in more than 1 in 10 people … Do not drive, cycle or use tools or machines if you feel dizzy or a bit shaky … Call your doctor or call 111 straight away if you're bruising more easily than normal or have bleeding that takes longer to stop","accessed":"2026-08-27"},{"id":"nhs_cet_about","url":"https://www.nhs.uk/medicines/cetirizine/about-cetirizine/","label":"NHS — About cetirizine (reviewed 17 Feb 2025)","quote":"cetirizine is classed as a non-drowsy antihistamine … some people still find it makes them feel quite sleepy. Do not drive or ride a bike if it makes you sleepy … headaches, dry mouth, feeling sick, feeling dizzy and diarrhoea … is available on prescription, and to buy from pharmacies and shops","accessed":"2026-08-27"},{"id":"nhs_cet_faq","url":"https://www.nhs.uk/medicines/cetirizine/common-questions-about-cetirizine/","label":"NHS — Common questions about cetirizine (reviewed 18 Feb 2025)","quote":"You should start to feel better within an hour after taking cetirizine … Cetirizine is unlikely to do you any harm if you take it for a long time … It's best not to drink alcohol while you're taking cetirizine as it can make you feel sleepy … You can eat and drink normally while taking cetirizine","accessed":"2026-08-27"},{"id":"nhs_cet_interact","url":"https://www.nhs.uk/medicines/cetirizine/taking-cetirizine-with-other-medicines-and-herbal-supplements/","label":"NHS — Taking cetirizine with other medicines and herbal supplements (reviewed 18 Feb 2025)","quote":"Check with your pharmacist or doctor if you're taking any medicine that makes you drowsy, gives you a dry mouth, or makes it difficult for you to pee … There might be a problem taking some herbal remedies and supplements alongside cetirizine, especially ones that cause sleepiness, a dry mouth, or make it difficult to pee","accessed":"2026-08-27"},{"id":"fda_zyrtec_otc","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b165db38-b302-4220-8627-77cb07bb078c","label":"DailyMed / FDA — ZYRTEC ALLERGY (cetirizine HCl 10 mg) film-coated tablet, OTC Drug Facts (effective 10 Oct 2025)","quote":"Cetirizine HCl 10 mg … Antihistamine … runny nose … sneezing … itchy, watery eyes … itching of the nose or throat … Ask a doctor before use if you have liver or kidney disease … Ask a doctor or pharmacist before use if you are taking tranquilizers or sedatives … drowsiness may occur … avoid alcoholic drinks … alcohol, sedatives, and tranquilizers may increase drowsiness … be careful when driving a motor vehicle or operating machinery … if breast-feeding: not recommended … if pregnant: ask a health professional before use … adults and children 6 years and over: one 10 mg tablet once daily; do not take more than one 10 mg tablet in 24 hours … adults 65 years and over: ask a doctor","accessed":"2026-08-27"},{"id":"fda_zyrtec_rx","url":"https://www.accessdata.fda.gov/drugsatfda_docs/label/2002/19835s15,%2020346s8lbl.pdf","label":"FDA — ZYRTEC (cetirizine hydrochloride) tablets and syrup, prescribing information (2002 label, NDA 19-835 / 20-346)","quote":"No clinically significant drug interactions have been found with theophylline at a low dose, azithromycin, pseudoephedrine, ketoconazole, or erythromycin … There was a small decrease in the clearance of cetirizine caused by a 400-mg dose of theophylline … Concurrent use of ZYRTEC with alcohol or other CNS depressants should be avoided because additional reductions in alertness and additional impairment of CNS performance may occur … given as a single daily dose, with or without food … The incidence of somnolence associated with ZYRTEC was dose related, 6% in placebo, 11% at 5 mg and 14% at 10 mg","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:14.713299+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."}