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ICD-10 R40.0
ICD-9 780.09

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Pratik Bahekar, MBBS [2]


Somnolence (or "drowsiness") is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods. It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm. The disorder characterized by the latter condition is most commonly associated with users of prescription hypnotics, such as mirtazapine or zolpidem.

It is considered a lesser impairment of consciousness than stupor or coma.


Causes by Organ System

Cardiovascular No underlying causes
Chemical/Poisoning No underlying causes
Dental No underlying causes
Dermatologic No underlying causes
Drug Side Effect Aldesleukin, Asenapine maleate, Aminoglutethimide, Amobarbital sodium, Apomorphine hydrochloride, Atropine, bicisate dihydrochloride,Butabarbital, Butorphanol, Carbinoxamine, Clemastine, Clobazam, Cimetidine, Cetirizine hydrochloride, Chlordiazepoxide,Clorazepate Dipotassium,Clozapine, Cycloserine, Cyproheptadine hydrochloride, Cefaclor, Desloratadine, Desmopressin, Dexchlorpheniramine, Diphenhydramine, Eslicarbazepine acetate, Estazolam, Ezogabine, Felbamate, Flavoxate, Fluphenazine, Flurazepam hydrochloride, Fluvoxamine, Fosphenytoin sodium, Granisetron, Glycopyrrolate, Hydroxyzine,Hydrocodone bitartrate and acetaminophen, Ivermectin, dextromethorphan hydrobromide, Ethosuximide, Loratadine, Meropenem, Mifepristone, Meprobamate,Mepenzolate bromide, Metipranolol, Mitomycin, Mitotane, Nabilone, Nelarabine, Oxazepam, Pergolide, Pentobarbital, Phenobarbital, Polymyxin B, Praziquantel, Pyrantel pamoate, Pyridoxine hydrochloride, Quazepam, Ramelteon, Rilpivirine, riluzole, Rotigotine, Secobarbital sodium, Sodium oxybate, Sulfasalazine,Suvorexant, tasimelteon,Terbutaline, Thioridazine hydrochloride, Thiothixene, Trimethobenzamide, Varenicline, Zopiclone
Ear Nose Throat No underlying causes
Endocrine No underlying causes
Environmental No underlying causes
Gastroenterologic No underlying causes
Genetic No underlying causes
Hematologic No underlying causes
Iatrogenic No underlying causes
Infectious Disease No underlying causes
Musculoskeletal/Orthopedic No underlying causes
Neurologic No underlying causes
Nutritional/Metabolic No underlying causes
Obstetric/Gynecologic No underlying causes
Oncologic No underlying causes
Ophthalmologic No underlying causes
Overdose/Toxicity No underlying causes
Psychiatric No underlying causes
Pulmonary No underlying causes
Renal/Electrolyte No underlying causes
Rheumatology/Immunology/Allergy No underlying causes
Sexual No underlying causes
Trauma No underlying causes
Urologic No underlying causes
Miscellaneous No underlying causes

Causes in Alphabetical Order



Somnolence can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued, he or she may experience microsleeps (loss of concentration).

See also


  1. Zimmermann C, Pfeiffer H (January 2007). "[Sleep disorders in depression. Suggestions for a therapeutic approach]". Nervenarzt (in German). 78 (1): 21–30. doi:10.1007/s00115-006-2111-1. PMID 16832696.
  2. Watanabe N, Omori IM, Nakagawa A; et al. (2011). "Mirtazapine versus other antidepressive agents for depression". Cochrane Database Syst Rev (12): CD006528. doi:10.1002/14651858.CD006528.pub2. PMID 22161405.
  3. "". External link in |title= (help)