Neurologic effects. Thiamine deficiency is common in chronic alcoholics; the principal lesions resulting from this deficiency are peripheral neuropathies and the Wernicke-Korsakoff syndrome (see
Table 8.9 and Chapter 23). Cerebral atrophy, cerebellar degeneration, and optic neuropathy may also occur.
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Cardiovascular effects. Alcohol has diverse effects on the cardiovascular system. Injury to the myocardium may produce dilated congestive cardiomyopathy (alcoholic cardiomyopathy), discussed in Chapter 11. Moderate amounts of alcohol (one drink per day) have been reported to increase serum levels of high-density lipoproteins (HDLs) and inhibit platelet aggregation, thus protecting against coronary artery disease. However, heavy consumption, with attendant liver injury, results in decreased levels of HDL, increasing the likelihood of heart disease. Chronic alcoholism also is associated with an increased incidence of hypertension.
Pancreatitis. Excess alcohol intake increases the risk of acute and chronic pancreatitis (Chapter 16).
Effects on fetus. The use of ethanol during pregnancy— reportedly even in low amounts—can cause fetal alcohol syndrome. It consists of microcephaly, growth retardation and facial abnormalities in the newborn, and a reduction of mental functions in older children. It is difficult to establish the amount of alcohol consumption that can cause fetal alcohol syndrome, but consumption during the first trimester of pregnancy is particularly harmful.
Carcinogenesis. Chronic alcohol consumption is associated with an increased incidence of cancers of the oral cavity, esophagus, liver, and, possibly, breast in females. The mechanisms of the carcinogenic effect are uncertain.
Malnutrition. Ethanol is a substantial source of energy, but is often consumed at the expense of food (empty calories). Chronic alcoholism is thus associated with malnutrition and deficiencies, particularly of the B vitamins.
Acutealcoholabusecausesdrowsinessatbloodlevelsofapproximately200mg/dL.Stuporandcomadevelopathigherlevels.
Alcoholisoxidizedtoacetaldehydeintheliverprimarilybyalcoholdehydrogenase,andtoalesserextentbythecytochromeP-450system,andbycatalase.Acetaldehydeisconvertedtoacetateinmitochondriaandisusedintherespiratorychain.
AlcoholoxidationbyalcoholdehydrogenasedepletesNAD,leadingtoaccumulationoffatintheliverandtometabolicacidosis.
Themaineffectsofchronicalcoholismarefattyliver,alcoholichepatitis,andcirrhosis,whichleadstoportalhypertensionandincreasestheriskfordevelopmentofhepatocellularcarcinoma.
Chronicalcoholismcancausebleedingfromgastritisandgastriculcers,peripheralneuropathyassociatedwiththiaminedeficiency,andalcoholiccardiomyopathy,anditincreasestheriskfordevelopmentofacuteandchronicpancreatitis.
Chronicalcoholismisamajorriskfactorforcancersoftheoralcavity,larynx,andesophagus.Theriskisgreatlyincreasedbyconcurrentsmokingortheuseofsmokelesstobacco.
InjurybyTherapeuticDrugs:AdverseDrugReactions
Adverse drug reactions (ADRs) are untoward effects of drugs that are administered in conventional therapeutic settings. These reactions are extremely common in the practice of medicine and are believed to affect 7% to 8% of patients admitted to a hospital. About 10% of such reactions prove fatal.