Page 254 - Textbook of Pathology, 6th Edition

238 Environmental chemicals e.g. long-term or accidental
exposure to certain man-made or naturally-occurring
chemicals.

THERAPEUTIC (IATROGENIC) DRUG INJURY
Though the basis of patient management is rational drug
therapy, nevertheless adverse drug reactions do occur in 2-
5% of patients. In general, the risk of adverse drug reaction
increases with increasing number of drugs administered.
SECTION I
Adverse effects of drugs may appear due to:
overdose;
genetic predisposition;
exaggerated pharmacologic response;
interaction with other drugs; and
unknown factors.
It is beyond the scope of this book to delve into the list of
drugs with their harmful effects. However, some of the
common forms of iatrogenic drug injury and the offending
drugs are listed in Table 9.2.

NON-THERAPEUTIC TOXIC AGENTS
ALCOHOLISM

Figure 9.2 Major adverse effects of tobacco smoking. Right side Chronic alcoholism is defined as the regular imbibing of an
shows smoking-related neoplastic diseases while left side indicates non- amount of ethyl alcohol (ethanol) that is sufficient to harm
neoplastic diseases associated with smoking, numbered serially in order an individual socially, psychologically or physically. It is
of frequency of occurrence.
difficult to give the number of ‘drinks’ after which the
diagnosis of alcoholism can be made because of differences
in the United States exceeding in incidence beyond that of in individual susceptibility. However, adverse effects—acute
breast cancer in that country. Cigarette smoking is strongly as well as chronic, are related to the quantity of alcohol
General Pathology and Basic Techniques
implicated in evolution of lung cancer as described in content imbibed and duration of consumption. Generally,
Chapter 17. 10 gm of ethanol is present in:

OTHER CANCERS. Besides lung cancer, smokers have a can of beer (or half a bottle of beer);
higher risk of development of cancer of upper aerodigestive 120 ml of neat wine; or
tract (lips, oral cavity, larynx, oesophagus), pancreas, urinary 30 ml of 43% liquor (small peg).
bladder and kidney. A daily consumption of 40 gm of ethanol (4 small pegs
or 2 large pegs) is likely to be harmful but intake of 100 gm
NON-NEOPLASTIC DISEASES. These include the or more daily is certainly dangerous. Daily and heavy
following: consumption of alcohol is more harmful than moderate social
i) Chronic obstructive pulmonary disease (COPD) that drinking since the liver, where ethanol is metabolised, gets
includes chronic bronchitis and emphysema as the most time to heal.
common.
ii) Peptic ulcer disease with 70% higher risk in smokers.
iii) Early menopause in smoker women. Metabolism
iv) In smoking pregnant women, higher risk of lower birth Absorption of alcohol begins in the stomach and small
weight of foetus, higher perinatal mortality and intellectual intestine and appears in blood shortly after ingestion. Alcohol
deterioration of newborn. is then distributed to different organs and body fluids
proportionate to the blood levels of alcohol. About 2-10% of
absorbed alcohol is excreted via urine, sweat and exhaled
CHEMICAL AND DRUG INJURY
through breath, the last one being the basis of breath test
During life, each one of us is exposed to a variety of chemicals employed by law-enforcement agencies for alcohol abuse.
and drugs. These are broadly divided into the following three Metabolism of alcohol is discussed in detail in Chapter 21;
categories: in brief alcohol is metabolised in the liver by the following 3
Therapeutic (iatrogenic) agents e.g. drugs, which when pathways (Fig. 9.3):
administered indiscriminately are associated with adverse By the major rate-limiting pathway of alcohol
effects. dehydrogenase (ADH) in the cytosol, which is then quickly
Non-therapeutic agents e.g. alcohol, lead, carbon monoxide, destroyed by aldehyde dehydrogenase (ALDH), especially
drug abuse. with low blood alcohol levels.