Adverse Drug Effects: A Nursing Concern

Pharmacokinetic effects – metabolism and excretion 31Table 2.4 The effect of liver cirrhosis on drug metabolism (Gibson and Skett, 1986)Drugs affectedDrugs not affected• Barbiturates • Lorazepam• Chlordiazepoxide • Morphine• Diazepam • Oxazepam• Methadone • Paracetamol• Salicylatesof sexual development (Gibson and Skett, 1986). The importance ofhormonal control is well established in rats and mice but has beenlittle regarded in clinical practice, perhaps due to lack of research inthis field in humans.Drug eliminationDrug elimination is the process by which a drug or its metabolite isexcreted from the body, and is considered to have occurred when95% of the drug is excreted. Elimination generally takes five plasmahalf-lives (Lovejoy and Matteis, 1996). The drug can be excreted viaany body fluid, including urine, bile, sweat, saliva, faeces, breast milkand across the placenta. Some drugs such as anaesthetic gases areeliminated in expired air; this route is also utilized for medico-legalpurposes in the breathalyser test to identify the alcohol concentrationin the expired air of vehicle drivers. However, the kidneystogether with the gall bladder are the most important organs fordrug excretion. Depending on metabolism the excreted drug may beactive or inactive. If the drug is still active then elimination is importantin getting rid of the drug and preventing it from building up inthe blood and becoming toxic. If the drug is in an inactive nonharmfulstate then the process of elimination is not quite so crucial.However, whether excreted in an active or inactive state concern isbeing expressed because the excreted drugs are ‘turning up in tapwater at concentrations to rival those of pesticides’ (Pearce, 1999).Glomerular filtrationThe term clearance is used to express removal of a drug from theblood, and is usually associated with the kidney. Renal clearance is