Skip to Content

Chloral Hydrate

Class: Anxiolytics, Sedatives, and Hypnotics; Miscellaneous
VA Class: CN309
CAS Number: 302-17-0
Brands: AquachloralSuprettes, Somnote


Genotoxic and may be carcinogenic in mice; should not be used when less potentially dangerous agents would be effective.103


Sedative and hypnotic.100 101 103 106

Uses for Chloral Hydrate


Short term treatment of insomnia for <2 weeks; effective for inducing and maintaining sleep.100 101 103


Used for routine sedation.100 101 106

Used preoperatively to relieve anxiety and to provide sedation100 101 without depressed respiration or cough reflex.103

Also used to produce sleep prior to non-painful procedures (e.g., EEG, diagnostic imaging)104 105 to relieve anxiety and to provide sedation.100 101 103

Has been used for conscious sedation to relieve anxiety in young pediatric patients (usually <3 years of age) during procedures (e.g., diagnostic imaging).104 105 106

Used often in geriatric and pediatric patients, because many clinicians suggest that the drug is associated with paradoxical excitement less frequently than barbiturates; however, no well controlled studies confirmed this clinical impression.100 101

Postoperative Analgesia

Adjunct to opiates and analgesics for control of postoperative pain.103


Reduction of anxiety associated with withdrawal of opiates or barbiturates.100 101 103

Used alone or in conjunction with paraldehyde for prevention of alcohol withdrawal symptoms and/or suppression of the syndrome once it develops.100 101

Chloral Hydrate Dosage and Administration


Administer orally100 101 or rectally.103

Withdraw chloral hydrate slowly after chronic administration to avoid possibility of precipitating withdrawal symptoms.101 c (See Withdrawal under Warnings and Precautions.)

Oral Administration

Administer capsules with a full glass of water or liquid after meals;101 dilute oral solution in 1/2 a glass of water or other liquid (e.g., fruit juice, ginger ale).100 101

Rectal Administration

Moisten finger and suppository with water before inserting suppository.103

Suppositories have been dissolved in cottonseed or olive oil and administered as a retention enema.c


Pediatric Patients


50 mg/kg or 1.5 g/m2 up to a maximum single dose of 1 g.100 101


18 mg/kg (325 mg/18 kg) once daily before bedtime.103

Routine Sedation

8 mg/kg or 250 mg/m2 3 times daily, up to a maximum of 500 mg 3 times daily.100 101

Some experts recommend a dosage of 25–50 mg/kg per 24 hours, (given in 3 or 4 doses; every 8 or 6 hours, respectively), up to 500 mg per dose.106


9 mg/kg (325 mg/36 kg), do not exceed 1 dose in 24 hours.103

Some experts recommend a dosage of 25–50 mg/kg per 24 hours, (given in 3 or 4 doses; every 8 or 6 hours, respectively), up to 500 mg per dose.106

Preoperative Sedation

8 mg/kg or 250 mg/m2 3 times daily, up to a maximum of 500 mg 3 times daily.100 101


9 mg/kg (325 mg/36 kg); do not exceed 1 dose in 24 hours.103

Procedural Sedation

20–25 mg/kg before procedure.100 101

Some experts recommend a 25- to 100-mg/kg dose before procedure; do not exceed a 1-g dose in infants or a 2-g dose in children.105 106


Some experts recommend a 25- to 100-mg/kg dose before procedure; do not exceed a 1-g dose in infants or a 2-g dose in children.106

Conscious Sedation†

Neonates: have been given 25–100 mg/kg once.104

Pediatric patients <3 years of age (excluding neonates): were given a dose of 25–100 mg/kg and a second dose of 25–50 mg/kg may be administered after 30 minutes; maximum total dosage has been 2 g or 100 mg/kg (whichever was lower).104 105


Some experts recommend a 25- to 100-mg/kg dose before procedure; do not exceed a 1-g dose in infants or a 2-g dose in children.106



0.5–1 g 15–30 minutes prior to bedtime.100 101

Some experts recommend a 0.5- to 1-g dose; do not exceed 2 g in 24 hours.106


0.65–1.3 g 30 minutes prior to bedtime.103

Some experts recommend a 0.5- to 1-g dose; do not exceed 2 g in 24 hours.106

Routine Sedation

250 mg 3 times daily after meals.100 101


325–650 mg 3 times daily, up to a maximum total daily dosage of 1950 mg.103

Some experts recommend 250 mg 3 times daily.106

Preoperative Sedation

0.5–1 g 30 minutes prior surgery.c

Alcohol Withdrawal

0.5–1 g every 6 hours as needed, up to a maximum single dose or daily dosage of 2 g.100 101

Prescribing Limits

Pediatric Patients


Maximum 1 g daily (as a single dose).100 101


For routine sedation, maximum 500 mg 3 times daily.100 101 c

For procedural sedation, maximum 1-g dose in infants or a 2-g dose in children.106

For conscious sedation, maximum total dosage in children <3 years of age (excluding neonates) is 2 g or 100 mg/kg (whichever is lower).104 105


For routine or preoperative sedation, maximum of one 9-mg/kg (325-mg/36 kg) dose daily.103



Maximum 2 g daily.100 101 c


Maximum 1950 mg daily.103

Special Populations

No special population recommendations at this time.100 101 c 103 (See Contraindications under Cautions.)

Cautions for Chloral Hydrate


  • Marked hepatic impairment.100 101 c 103

  • Marked renal impairment. 100 101 c 103

  • Known hypersensitivity or idiosyncratic reaction to chloral hydrate.100 101 c 103




Although the manufacturer of Aquachloral suppositories warns about potential carcinogenicity of the drug, some experts state that the assumption that chloral hydrate is a reactive metabolite of trichloroethylene (an industrial solvent) responsible for the carcinogenicity of trichloroethylene is questionable.108 There is evidence that the carcinogenicity of trichloroethylene is due to a reactive intermediate epoxide metabolite rather than to chloral hydrate.108

Abuse Potential

Although uncommon, tolerance and psychologic dependence may occur following prolonged administration of the drug; use with caution in patients with a history of drug abuse.100 101 c 103

Symptoms of dependence are similar to those of chronic alcoholism100 101 c 103 (drowsiness, lethargy, hangover, slurring of speech, incoordination, tremulousness, and nystagmus).c


Sudden withdrawal may cause delirium tremens (sometimes fatal) and hallucinations; following chronic use, withdraw slowly.100 101 c 103

Sensitivity Reactions

Hypersensitivity Reactions

Scarlatiniform or erythematous rash, urticaria, angioedema, purpura, eczema, bullous lesions, skin eruptions, and erythema multiforme reported, sometimes accompanied by fever.100 101 103

Tartrazine Sensitivity

Aquachloral 325 mg rectal suppositories contain tartrazine (FD&C yellow No. 5), which may cause allergic reactions including bronchial asthma in susceptible individuals.103 Incidence of tartrazine sensitivity is low, but it frequently occurs in patients who are sensitive to aspirin.103

General Precautions

CNS Effects

Use with caution in mentally depressed patients or those having suicidal tendencies.100 101 c 103

Rarely, somnambulistic reaction characterized by disorientation and incoherence reported.100 101 103

GI Effects

Avoid oral administration in patients with esophagitis, gastritis, or gastric or duodenal ulcers.100 101 c

Gastritis may develop following prolonged oral administration; minimize irritation by diluting oral syrup or administering other oral dosage forms with liquids.100 101 c (See Administration under Dosage and Administration.)

Cardiac Effects

Prolonged administration of therapeutic doses was not associated with adverse cardiac effects.100 101 103

Do not use high doses in patients with severe cardiac disease.100 101 103

Renal Effects

Following prolonged administration, parenchymatous renal damage reported.100 101


Attacks of acute intermittent porphyria reported; use caution in susceptible patients.101

Adequate Monitoring

Procedural sedation using chloral hydrate in pediatric patients should be performed only under the supervision of qualified clinicians experienced in cardiorespiratory complications.104 105 107

Specific Populations


Category C.100 101 c 103


Distributed into milk.103 Use with caution in nursing women.100 101 c 103

Pediatric Use

Used orally and rectally in pediatric patients for sedation and hypnosis.100 101 c 103 104 105 106 108

Geriatric Use

Geriatric patients may tolerate chloral hydrate even when intolerant to barbiturates.103

Common Adverse Effects

Nausea,100 101 c 103 vomiting, 100 101 c 103 diarrhea, 100 101 c 103 ataxia, 100 101 c 103 dizziness.100 101 c 103

Interactions for Chloral Hydrate

Specific Drugs




CNS depressants (e.g., alcohol, barbiturates, paraldehyde )

Additive CNS depression100 101 103

Vasodilation (characterized by tachycardia, palpitations, facial flushing, and dysphoria) may occur when used with alcohol100 101 103

Use with caution to avoid overdosage100 101 103


Possible diaphoresis, flushing, variable BP, uneasiness, in patients with acute MI and CHF receiving IV furosemide within 24 hours of chloral hydrate100 101

Consider alternative hypnotic drug (e.g., a benzodiazepine) in patients receiving IV furosemide100 101 c


Potential for increased warfarin metabolism and decreased warfarin efficacy (hypoprothrombinemia)100 101 c 103

Consider alternative hypnotic drug e.g., benzodiazepine).100 101 c If used concomitantly, monitor prothrombin time closely100 101 c 103

Tests for Urine Glucose

Possible false-positive results in urine glucose test using cupric sulfate as Benedict’s solution and possibly with cupric sulfate tablets (Clinitest)100 101 c

May use glucose tests based on enzymatic glucose oxidase reactions (e.g., Clinistix, Tes-Tape)100 101 c

Urine Catecholamine Test (Fluorometric)

Possible interference 100 101

Do not administer chloral hydrate for 48 hours prior to test100 101 c

Urinary 17-hydroxycorticosteroids Test

Possible interference with Reddy, Jenkins, and Thorn procedures100 101 c

Chloral Hydrate Pharmacokinetics



Rapidly absorbed following oral or rectal administration.c


Following oral administration of 0.5–1 g, sedation occurs within 30–60 minutes.c 105

Following rectal administration, sedation occurs within 60 minutes.103


Following oral administration of 0.5–1 g : 4–8 hours.c 105



Distributed into CSF, umbilical cord blood, fetal blood, amniotic fluid, and milk.100 101 c



Metabolized to trichloroethanol (active metabolite), principally in the liver and erythrocytes, by alcohol dehydrogenase and other enzymes.c Small, but variable amounts of chloral hydrate metabolized to trichloroacetic acid (inactive metabolite) in liver and kidneys.c

Elimination Route

Active and inactive metabolites are slowly and variably excreted in the kidneys.c Trichloroethanol glucuronide (urochloralic acid), an inactive metabolite, may be secreted into the bile and excreted in feces.c

Eliminated by dialysis.103


8–11 hours.c





25°C (may be exposed to 15–30°C).101


Tight, light resistant containers at 20–25°C; protect from freezing.100



15–30°C; do not refrigerate.c 103


  • Mechanism of action not fully elucidated; CNS depressant effect believed to result primarily from active metabolite trichloroethanol.c 103

  • CNS depressant effects similar to paraldehyde and barbiturates.c

  • Hypnotic doses produce mild cerebral depression and quiet, deep sleep.c

  • Higher doses may lead to general anesthesia and concurrent depression of respiratory and vasomotor centers; death may result from respiratory failure.c

  • Sedative or hypnotic doses have little anticonvulsant activity.c

  • Has little analgesic activity and may produce excitement or delirium in the presence of pain.c

Advice to Patients

  • Administer capsules with a full glass of water or liquid101 and oral solution with half glass of liquid (i.e., water, fruit juice, or ginger ale).100 (See Administration under Dosage and Administration)

  • Advise patients not to take CNS depressant drugs or alcohol concomitantly with chloral hydrate.100 101 103

  • Risk of dizziness or fatigue; potential for drug to impair mental alertness or physical coordination; use caution when driving or operating machinery until effects on the individual are known.100 101 c 103

  • Importance of informing clinicians of hypersensitivity to aspirin.103 (See Tartrazine Sensitivity under Warnings and Precautions.)

  • Importance of informing clinicians of existing or contemplated therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as concomitant illnesses.100 101 c 103

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed; breast-feeding may result in sedation of the infant.c 103

  • Importance of informing patients of other important precautionary information. (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Chloral hydrate is subject to control under the Federal Controlled Substances Act of 1970 as a schedule IV (C-IV) drug.c

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Chloral Hydrate


Dosage Forms


Brand Names



Capsules, liquid-filled

500 mg*

Somnote (C-IV)



500 mg/5 mL*

Chloral Hydrate Syrup (C-IV)

Pharmaceutical Associates



325 mg

Aquachloral Supprettes (with tartrazine, C-IV)

Amerifit Pharma

500 mg

Chloral Hydrate Suppositories (C-IV)


650 mg

Aquachloral Supprettes (with tartrazine, C-IV)

Amerifit Pharma

AHFS DI Essentials™. © Copyright 2019, Selected Revisions April 1, 2009. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.


100. Pharmaceutical Associates. Chloral hydrate syrup prescribing information. Greenville, SC; 2002 Oct.

101. Breckenridge Pharmaceutical. Somnote capsules prescribing information. Boca Raton, FL; 2004 Dec.

103. Amerifit Pharma. AquachloralSupprettes prescribing information. Woburn, MA; 2006 May.

104. Krauss B, Green SM. Sedation and analgesia for procedures in children. N Engl J Med. 2000; 342:938-45.

105. Sectish TC. Use of sedation and local anesthesia to prepare children for procedures. Am Fam Physician. 1997; 55:909-16.

106. Siberry GK, Iannone R, eds. The Harriet Lane handbook: a manual for pediatric house officers. 15th ed. Philadelphia, PA: Mosby: 2000:667.

107. American Academy of Pediatrics, American Academy of Pediatric Dentistry, Coté CJ, Wilson S, and the Work Group on Sedation. Guidelines for monitoring and management of pediatric patients during and after sedation for diagnostic and therapeutic procedures; an update. Pediatrics. 2006; 118::836-8.

108. American Academy of Pediatrics Committee on Drugs and Committee on Environmental Health. Use of chloral hydrate for sedation in children. Pediatrics. 1993; 92:471-3.

c. AHFS drug information 2007. McEvoy GK, ed. Chloral hydrate. Bethesda, MD: American Society of Health-System Pharmacists; 2007;2547-8.