CHAPTER 2-89: ISOPROPYL ALCOHOL

INTRODUCTION

Isopropyl alcohol is a clear, colorless liquid with a bitter taste used widely in a solvent, an antiseptic, and a disinfectant and is commonly available in the home as a 70% solution (rubbing alcohol). It is often ingested by alcoholics as a cheap substitute for liquor. Unlike the other common alcohol substitutes methanol and ethylene glycol, isopropyl alcohol is not metabolized to highly toxic organic acids and therefore does not produce a profound anion gap acidosis.

MECHANISM OF TOXICITY

1. Isopropyl alcohol is a potent depressant of the CNS, and intoxication by ingestion or inhalation may result in coma and respiratory arrest. It is metabolized to acetone (dimethyl ketone), which may contribute to and prolong CNS depression.

2. Very large doses of isopropyl alcohol may cause hypotension secondary to vasodilation and possibly myocardial depression.

3. Isopropyl alcohol is irritating to the GI tract and commonly causes gastritis.

4. Chronic inhalation of isopropyl alcohol can cause respiratory tract irritation. Chronic exposure has also been associated with elevated hepatic transaminases, dementia, cerebellar dysfunction, and myopathy.

5. Pregnancy. Isopropyl alcohol crosses the placenta and is associated with decreased birth weight in animals.

6. Pharmacokinetics. Isopropyl alcohol is rapidly absorbed with peak levels 30 minutes after ingestion. It can also be absorbed dermally and by inhalation. It distributes into body water (volume of distribution, 0.6 L/kg). It is metabolized (half-life, 2.5–8 hours) by alcohol dehydrogenase to acetone. Up to 20% is excreted unchanged in the urine.

TOXIC DOSE

Isopropyl alcohol is approximately two- to threefold more potent than ethanol.

1. Ingestion. The toxic oral dose is about 0.5–1 mL/kg of rubbing alcohol (70% isopropyl alcohol) but varies depending on individual tolerance and whether any other depressants were ingested. Fatalities have occurred after adult ingestion of 240 mL, but patients with ingestions of up to 1 L have recovered with supportive care.

2. Inhalation. The odor of isopropyl alcohol can be detected at an air level of 40–200 ppm. The OSHA Permissible Exposure Limit (PEL) is 400 ppm (983 mg/m³) as an 8-hour time-weighted average. The air level considered immediately dangerous to life or health (IDLH) is 2,000 ppm. Toxicity has been reported in children after isopropyl alcohol sponge baths, probably as a result of inhalation rather than skin absorption.

CLINICAL PRESENTATION

Intoxication mimics drunkenness from ethanol, with slurred speech, ataxia, and stupor followed in large ingestions by coma, hypotension, and respiratory arrest.

1. Because of the gastric-irritant properties of isopropyl alcohol, abdominal pain and vomiting are common, and hematemesis occasionally occurs.

2. Metabolic acidosis may occur but is usually mild. The osmol gap is usually elevated. The serum creatinine may be falsely elevated (eg, 2–3 mg/dL) owing to interference with the laboratory method.

3. Isopropyl alcohol is metabolized to acetone, which contributes to CNS depression and gives a distinct odor to the breath (in ...