McKenna's Pharmacology, 2e

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P A R T 1  Introduction to nursing pharmacology

Alterations in glucose metabolism All cells need glucose for energy; the cells of the central nervous system are especially dependent on constant glucose levels to function properly. The control of glucose in the body is an integrated process that involves a series of hormones and enzymes that use the liver as the place for glucose storage or release. Many drugs have an impact on glucose levels because of their effects on the liver or the endocrine system. Hypoglycaemia Some drugs affect metabolism and the use of glucose, causing a low serum blood glucose concentration, or hypoglycaemia. Glipizide and glibenclamide are antidia­ betic agents that have the desired action of lowering the blood glucose level but can lower blood glucose too far, causing hypoglycaemia. Assessment Symptoms may include fatigue; drowsiness; hunger; anxiety; headache; cold, clammy skin; shaking and lack of coordination (tremulousness); increased heart rate; increased blood pressure; numbness and tingling of the mouth, tongue and/or lips; confusion; and rapid and shallow respirations. In severe cases, seizures and/or coma may occur. Interventions Restore glucose—orally, if possible, or intravenously (IV). Provide supportive measures (e.g. skin care, environmental control of light and temperature, rest). Institute safety measures to prevent injury or falls. Monitor blood glucose levels to help stabilise the situa­ tion. Offer reassurance to help the person cope with the experience. Hyperglycaemia Some drugs stimulate the breakdown of glycogen or alter metabolism in such a way as to cause high serum glucose levels, or hyperglycaemia. Ephedrine (generic), a drug used as a bronchodilator and antiasthma drug and to relieve nasal congestion, can break down stored glycogen and cause an elevation of blood glucose by its effects on the sympathetic nervous system. Diazoxide, a drug used for treatment of malignant hypertension, causes a decrease in insulin release, leading to an increase in blood glucose levels. Assessment Fatigue, increased urination (polyuria), increased thirst (polydipsia), deep respirations (Kussmaul respirations), restlessness, increased hunger (polyphagia), nausea, hot or flushed skin and fruity breath odour may be observed. Interventions Administer insulin therapy to decrease blood glucose as appropriate, while carefully monitoring glucose levels.

Liver injury (hepatotoxicity) Oral drugs are absorbed and passed directly into the liver in the first-pass effect. This exposes the liver cells to the full impact of the drug before it is broken down or distributed throughout the body. Most drugs are metabolised in the liver, so any active metabolites that are toxic will also affect the integrity of the liver cells (hepatocytes). Assessment Symptoms may include fever, malaise, nausea, vomiting, jaundice, change in colour of urine or stools, abdomi­ nal pain or colic, elevated liver enzymes (e.g. aspartate aminotransferase [AST], alanine aminotransferase [ALT]), alterations in bilirubin levels and changes in clotting factors (e.g. partial thromboplastin time). Interventions Discontinue the drug and notify the prescriber and/or primary caregiver. Offer supportive measures such as small, frequent meals, skin care, a cool environment and rest periods. Renal injury (nephrotoxicity) The glomerulus in the kidney has a very small capil­ lary network that filters the blood into the renal tubule. Some drug molecules can precipitate in the renal tubules causing acute inflammation and severe renal problems. Some drugs are excreted from the kidney unchanged; they have the potential to directly affect the renal tubule and alter normal absorption and secretion processes. Gentamicin, a potent antibiotic, is frequently associated with renal toxicity. Assessment Elevated blood urea nitrogen (BUN), elevated creatinine concentration, decreased haematocrit, electrolyte imbal­ ances, fatigue, malaise, oedema, irritability and skin rash may be seen. Interventions Notify the prescriber and/or primary caregiver and discontinue the drug as needed. Offer supportive measures—for example, positioning, diet and fluid restrictions, skin care, electrolyte therapy, rest periods, a controlled environment. In severe cases, be aware that dialysis may be required for survival. Poisoning Poisoning occurs when an overdose of a drug damages multiple body systems, leading to the potential for fatal reactions. Assessment parameters vary with the par­ ticular drug. Treatment of drug poisoning also varies, depending on the drug. Throughout this book, specific treatments for poisoning are identified, if known. Emer­ gency and life support measures are often needed in severe cases.