Somnolence

# Overview
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

## Causes by Organ System

## Causes in Alphabetical Order
- Apomorphine hydrochloride
- Butorphanol
- Cimetidine
- Cycloserine
- Cyproheptadine hydrochloride
- Desloratadine
- Estazolam
- Granisetron
- Mifepristone
- Nabilone
- Pyrantel pamoate
- Pergolide
- Ramelteon
- Rilpivirine
- Sodium oxybate
- Tasimelteon
- Terbutaline
- Thioridazine hydrochloride

# Causes
- Advanced sleep phase disorder
- African trypanosomiasis ("sleeping sickness")
- Alice in Wonderland syndrome
- Brain edema
- Cerebral hypoxia
- Chronic fatigue syndrome
- Clinical depression, especially seasonal affective disorder
- Dehydration
- Delayed sleep phase syndrome
- Desmopressin
- Diabetic ketoacidosis as example, but not balanced diabetes mellitus
- Drug Side Effect- Bicisate dihydrochloride,Brompheniramine maleate and Pseudoephedrine hydrochloride, caspofungin acetate, Clozapine, Cyclobenzaprine, Eletriptan, Fesoterodine, Ketorolac tromethamine, Levetiracetam, Loratadine, Naproxen sodium, Oxcarbazepine, Prochlorperazine, Progesterone
- Encephalitis  (viral, bacterial or other agents)
- Epilepsy
- Fibromyalgia
- Hydrocephalus
- Hyperparathyroidism
- Hypothermia
- Hypothyroidism
- Increased intracranial pressure; for example, brain tumors
- Infectious mononucleosis (glandular fever)
- Intracranial hemorrhage such as due to ruptured aneurysm
- Lyme disease
- Medications
Analgesics: mostly prescribed or illicit opiates such as oxycontin or heroin
Antiepileptics such as phenytoin, carbamazepine, gabapentin, topiramate
Antidepressants: for instance sedating tricyclic antidepressants and mirtazapine.  Somnolence is less common with SSRI and SNRI as well as MAOI.
Antihistamines: diphenhydramine, doxylamine, Loratadine and Olopatadine
Antipsychotics: clozapine, thioridazine, quetiapine, olanzapine, risperidone, and ziprasidone but not haloperidol
Dopamine agonists used in the treatment of parkinson's disease e.g. pergolide, ropinirole and pramipexole.
HIV medications for example, efavirenz
Antihypertensive medications like amlodipine
Hypnotics like zopiclone, or the benzodiazepine such as diazepam or nitrazepam and the barbiturate, such as amobarbital or secobarbital
Central nervous system agents like Carisoprodol, Metaxalone
Other agents impacting the central nervous system in sufficient or toxic doses
Melatonin
Spironolactone
- Analgesics: mostly prescribed or illicit opiates such as oxycontin or heroin
- Antiepileptics such as phenytoin, carbamazepine, gabapentin, topiramate
- Antidepressants: for instance sedating tricyclic antidepressants and mirtazapine.  Somnolence is less common with SSRI and SNRI as well as MAOI.
- Antihistamines: diphenhydramine, doxylamine, Loratadine and Olopatadine
- Antipsychotics: clozapine, thioridazine, quetiapine, olanzapine, risperidone, and ziprasidone but not haloperidol
- Dopamine agonists used in the treatment of parkinson's disease e.g. pergolide, ropinirole and pramipexole.
- HIV medications for example, efavirenz
- Antihypertensive medications like amlodipine
- Hypnotics like zopiclone, or the benzodiazepine such as diazepam or nitrazepam and the barbiturate, such as amobarbital or secobarbital
- Central nervous system agents like Carisoprodol, Metaxalone
- Other agents impacting the central nervous system in sufficient or toxic doses
- Melatonin
- Spironolactone
- Sleep apnea
- Starvation
- Stroke
- Traumatic brain injury
- Treatment of primary insomina may cause somnolence:
Flurazepam
Benzodiazepine
Quazepam
Estazolam
Temazepam
Triazolam
Benzodiazepine receptor agonists: Eszopiclone, Zolpidem, Zaleplon
Melatonin receptor agonists: Ramelteon
- Flurazepam
- Benzodiazepine
- Quazepam
- Estazolam
- Temazepam
- Triazolam
- Benzodiazepine receptor agonists: Eszopiclone, Zolpidem, Zaleplon
- Melatonin receptor agonists: Ramelteon

# Hazards
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).