Classifications: central nervous system agent; anticonvulsant; sedative-hypnotic; barbiturate
Prototype: Phenobarbital
Pregnancy Category: C
Controlled Substance: Schedule IV


1 g/mL liquid


Cyclic ether formed by polymerization of acetaldehyde.

Therapeutic Effects

Potent CNS depressant with sedative and hypnotic actions similar to those of alcohol, barbiturates, and chloral hydrate.


Sedative and hypnotic in acute agitation due to alcohol withdrawal; used to control convulsions arising from tetanus, eclampsia, Status Epilepticus, and drug poisoning. Has been used rectally to induce basal anesthesia, particularly in children.


Severe hepatic insufficiency; respiratory disease; GI inflammation or ulceration; disulfiram therapy; pregnancy (category C), lactation.

Route & Dosage

Adult: PO 10–30 mL prn
Child: PO 0.3 mL/kg

Adult: PO 5–10 mL prn
Child: PO 0.15 mL/kg

Seizures Secondary to Tetanus
Adult: PO up to 12 mL diluted 1:10 q4h prn

Seizures Secondary to Other Poisons
Adult: PR 5–15 mL diluted in 200 mL per rectal tube

Status Epilepticus
Child: PR 1 mL/y of age up to 5 mL; may repeat in 1 h if necessary, then change to PO. PO 2–5 mL q2–4h

Alcohol Withdrawal Seizures
Adult: PO 5–10 mL q4–6h for 24 h, then q6h prn


Note: Both oral and rectal doses must be diluted before they are administered.


Adverse Effects (1%)

Body as a Whole: Occasionally confusion and paradoxical excitement. CNS: Hangover, dizziness, ataxia. CV: Hypotension, dilation and failure of right heart, cardiovascular collapse. GI: Irritation of mucous membrane (oral and rectal routes), nausea, vomiting, unpleasant taste and odor, toxic hepatitis, bleeding gastritis, liver damage. Urogenital: Nephrosis, renal damage. Metabolic: Metabolic acidosis, acidosis. Respiratory: Rapid labored breathing, respiratory depression, pulmonary hemorrhage and edema. Skin: Erythematous skin rash.

Diagnostic Test Interference

Chronic use of alcohol (ethanol) and paraldehyde may cause false-positive serum ketones (nitroprusside tube dilution method) and urine ketones (Acetest) and may interfere with urinary steroid (17-OHCS) determinations by modification of Reddy, Jenkins, Thorn procedure.


Drug: Disulfiram may increase paraldehyde levels; alcohol and other cns depressants add to CNS depressant effects—fatalities reported with alcohol.


Absorption: Readily absorbed from GI tract. Onset: 10–15 min. Duration: 6–8 h. Distribution: Distributed into CNS; crosses placenta. Metabolism: 80–90% of doses metabolized in liver. Elimination: Excreted through lungs (11–28%) and urine. Half-Life: 7.5 h.

Nursing Implications

Assessment & Drug Effects

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug