Hydroxycin is an antihistamine which, in addition to treating allergic conditions (chronic itching and hives), is also used to relieve anxiety and tension, as well as sleep and insomnia. Hydroxycin is commercially available in tablet or syrup form.



The antihistamine and antiallergic effects are based on hydroxycin blocking the H1 histamine receptor and actively attenuating its activity. By affecting neurotransmitter systems in the brain, the drug also has sedative, tranquilizing, and antispasmodic effects. The effects of hydroxycin occur within 15 to 60 minutes and last up to 6 hours.


After oral administration, hydroxycin is rapidly absorbed from the gastrointestinal tract and reaches maximum plasma concentration after approximately 2 hours. The drug is metabolized in the liver by the CYP3A4 and CYP3A5 enzymes. 70% of the active intermediate hydroxyzine is excreted in the urine. The half-life in children, adults, and the elderly is approximately 7, 20, and 29 hours, respectively.


Hydroxycin should not be taken in case of:

  • Hypersensitivity
  • severe liver or kidney failure
  • Prostate enlargement
  • Narrow-angle glaucoma
  • Porphyrias
  • pregnancy and breastfeeding

Drug interactions

Interactions with alcohol, central depressant drugs, MAO inhibitors, parasympathomimetics, and antihypertensives are possible with concomitant use, as well as with betahistine, epinephrine, phenytoin, and cimetidine.


Side effects

Drowsiness, dullness, headache, and dry mouth are common with the use of hydroxycin.

Toxicological data

Severe sedation is most common with overdose, but convulsions, drowsiness, nausea, or vomiting often occur LD50 (rat, oral): 840 mg/kg LD50 (mouse, oral): 400 mg/kg

Chemical & physical properties

Formula C21H27CIN2O2
Molar Mass (g·mol−1) 374,904
Physical State solid
Melting Point (°C) 200
Boiling Point (°C) 220
PKS Value 2,47
CAS Number 68-88-2
PUB Number 3658
Drugbank ID DB00557

Editorial principles

All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.
Markus Falkenstätter, BSc

Markus Falkenstätter, BSc

Markus Falkenstätter is a writer on pharmaceutical topics in Medikamio's medical editorial team. He is in the last semester of his pharmacy studies at the University of Vienna and loves scientific work in the field of natural sciences.

Mag. pharm. Stefanie Lehenauer

Mag. pharm. Stefanie Lehenauer

Stefanie Lehenauer has been a freelance writer for Medikamio since 2020 and studied pharmacy at the University of Vienna. She works as a pharmacist in Vienna and her passion is herbal medicines and their effects.

The content of this page is an automated and high-quality translation from DeepL. You can find the original content in German here.


Your personal medicine assistent

afgis-Qualitätslogo mit Ablauf Jahr/Monat: Mit einem Klick auf das Logo öffnet sich ein neues Bildschirmfenster mit Informationen über medikamio GmbH & Co KG und sein/ihr Internet-Angebot: medikamio.com/ This website is certified by Health On the Net Foundation. Click to verify.

Search our database for drugs, sorted from A-Z with their effects and ingredients.


All substances with their common uses, chemical components and medical products which contain them.


Causes, symptoms and treatment for the most common diseases and injuries.

The contents shown do not replace the original package insert of the medicinal product, especially with regard to dosage and effect of the individual products. We cannot assume any liability for the correctness of the data, as the data was partly converted automatically. A doctor should always be consulted for diagnoses and other health questions. Further information on this topic can be found here.