Classifications: anticonvulsant; sedative-hypnotic; barbiturate;
Therapeutic: anticonvulsant
; sedative-hypnotic
Prototype: Phenobarbital
Pregnancy Category: C
Controlled Substance: Schedule IV


1 g/mL liquid


Cyclic ether formed by polymerization of acetaldehyde. Potent CNS depressant with sedative and hypnotic actions similar to those of alcohol, barbiturates, and chloral hydrate.

Therapeutic Effect

CNS depressant with sedative and hypnotic effects. Also has anticonvulsant properties.


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.

  • Note: On exposure to light, air, and heat, drug liberates acetaldehyde, which oxidizes to acetic acid. Do not use solution if it is colored in any way or smells of acetic acid (vinegar odor).
  • Discard unused contents of any container that has been open for more than 24 h. Decomposed paraldehyde is extremely corrosive to tissues and can cause fatal poisoning.
  • Do not use plastics for measuring or administering paraldehyde. Contact with plastic materials can decompose paraldehyde to toxic compounds. Draw parenteral preparation into a glass syringe; use rubber catheter for rectal administration.
  • Give oral drug well diluted in iced fruit juice or milk to reduce irritation of GI tract and mask odor and taste.
  • When given rectally, dilute drug with at least 2 volumes of olive oil or cottonseed oil or dissolved in 200 mL of NS solution to prevent rectal irritation.
  • Do not withdraw rapidly after prolonged use; may produce delirium tremens and hallucinations.
  • Preserve in tight, light-resistant containers in amounts not exceeding 30 mL and at temperatures not over 25° C (77° F).

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

  • Monitor cardiovascular and respiratory status closely.
  • Keep the patient turned on side to prevent aspiration since bronchial secretions may be increased. Suctioning may be necessary.
  • Be aware that patient's breath will have a characteristic odor for several hours.

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

© 2006-2022 Last Updated On: 05/17/2022 (0)
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