Chapter 185: Alcohols

INTRODUCTION

All alcohols cause clinical inebriation, with the strength of the inebriating effects directly proportional to the alcohol's molecular weight; hence, at the same concentration, isopropanol is more intoxicating than ethanol (Figure 185–1).

Primary toxicity can be due to the parent compound (ethanol and isopropanol) or to toxic metabolites (ethylene glycol and methanol). Ethanol and isopropanol are the most common alcohols ingested; their principal effects are GI irritation and intoxication; and they do not in themselves produce metabolic acidosis. Methanol and ethylene glycol are toxic alcohols because they cause serious physiologic morbidity.

ETHANOL

INTRODUCTION

Ethanol (CH₃CH₂OH, molecular weight 46.07) is a colorless, volatile liquid that is the most frequently used and abused drug in the world. Morbidity from acute ethanol intoxication is usually related to secondary injuries rather than direct toxic effects. Toxicity most commonly occurs from ingestion, but ethanol may also be absorbed via inhalation or percutaneous exposure.

Ethanol is readily available in many different forms. A standard alcoholic beverage, such as 12 oz (355 mL) of beer (2% to 6% ethanol by volume), 5 oz (148 mL) of wine (10% to 20% ethanol by volume), or 1.5 oz (44 mL) of 80-proof spirits (40% ethanol by volume), contains about 15 grams of ethanol. Ethanol may be found in high concentrations in many other common household products such as mouthwash (may contain up to 75% ethanol by volume), colognes and perfumes (up to 40% to 60%), and as a diluent or solvent for medications (concentration varies widely between 0.4% and 65%). Such products are often flavored or brightly colored and may be attractive to children.

PATHOPHYSIOLOGY

Ethanol is rapidly absorbed after oral administration, and blood levels peak about 30 to 60 minutes after ingestion. The presence of food in the stomach prolongs absorption and delays the peak blood level. High concentrations of ethanol in the stomach may cause pylorospasm delaying gastric emptying. Some ethanol is broken down in the stomach by gastric alcohol dehydrogenase, which lowers the amount available for absorption. This enzyme is present at higher levels in men than in women, which may account for the fact that women usually develop a higher blood ethanol level than men after consuming the same dose per kilogram of body weight. The volume of distribution of ethanol is also gender dependent due to difference in body fat percentages: 0.6 L/kg in men and 0.7 L/kg in women.

Ethanol is a CNS depressant¹ that enhances the inhibitory neurotransmitter γ-aminobutyric acid receptors and blockade of excitatory N-methyl-d-aspartic acid receptors. Modulation of these systems leads to the development of tolerance, dependence, and a withdrawal syndrome when ...