CLINICAL PHARMACOLOGY 2003 (PART 10)

Background Definitions Causation: degrees of certainty Pharmacovigilance and pharmacoepidemiology Classification Causes Allergy in response to drugs Effects of prolonged administration: chronic organ toxicity Adverse effects on reproductionBackgroundCurd yesterday of my disease I died last night of my physician.1 Nature is neutral, i.e. it has no intentions towards humans, though it is often unfavourable to them. It is mankind, in its desire to avoid suffering and death, that decides that some of the biological effects of drugs are desirable (therapeutic) and others are undesirable (adverse). In addition to this arbitrary division, which has no fundamental biological basis,1From, The remedy worse...
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CLINICAL PHARMACOLOGY 2003 (PART 10) 8 Unwanted effects and adverse drug reactions SYNOPSIS unwanted effects of drugs are promoted, or even caused, by numerous nondrug factors. Because of Background the variety of these factors, attempts to make a Definitions simple account of the unwanted effects of drugs Causation: degrees of certainty must be imperfect. Pharmacovigilance and There is general agreement that drugs prescribed pharmacoepidemiology for disease are themselves the cause of a serious Classification amount of disease (adverse reactions), ranging from Causes mere inconvenience to permanent disability and Allergy in response to drugs death. Effects of prolonged administration: chronic Since drugs are intended to relieve suffering, organ toxicity patients find it peculiarly offensive that they can also Adverse effects on reproduction cause disease (especially if they are not forewarned). Therefore it is important to know how much dis- ease they do cause and why they cause it, so that preventive measures can be taken. It is not enough to measure the incidence of adverse reactions to drugs, their nature and their Background severity, though accurate data are obviously useful. It is necessary to take, or to try to take, into acc- Curd yesterday of my disease ount which effects are avoidable (by skilled choice I died last night of my physician.1 and use) and which are unavoidable (inherent in drug or patient). Also, different adverse effectsNature is neutral, i.e. it has no intentions towards can matter to a different degree to differenthumans, though it is often unfavourable to them. It is people.mankind, in its desire to avoid suffering and death, Since there can be no hope of eliminating allthat decides that some of the biological effects of adverse effects of drugs it is necessary to evaluatedrugs are desirable (therapeutic) and others are patterns of adverse reaction against each other. Oneundesirable (adverse). In addition to this arbitrary drug may frequently cause minor ill-effects butdivision, which has no fundamental biological basis, pose no threat to life, though patients do not like it and may take it irregularly, to their own detriment.1 From, The remedy worse than the disease. Matthew Prior Another drug may be pleasant to take, so that(1664-1721). patients take it consistently, with benefit, but it may 135 8 UNWANTED EFFECTS AND A D V E R S E DRUG REACTIONSrarely kill someone. It is not obvious which drug is altered by antibiotics; diuretic-induced hypokalaemiato be preferred. causing digoxin intolerance. Some patients, e.g. those with a history of allergyor previous reactions to drugs, are up to four times Intolerance means a low threshold to the normalmore likely to have another adverse reaction, so pharmacodynamic action of a drug. Individualsthat the incidence does not fall evenly. It is also vary greatly in their susceptibility to drugs, those atuseful to discover the causes of adverse reactions, one extreme of the normal distribution curve beingfor such knowledge can be used to render avoid- intolerant of the drugs, those at the other, tolerant.able what are at present unavoidable reactions. Avoidable adverse effects will be reduced by Idiosyncrasy (see Pharmacogenetics) implies anmore skilful prescribing and this means that inherent qualitative abnormal reaction to a drug,doctors, amongst all the other claims on their usually due to genetic abnormality, e.g. porphyria.time, must ...