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Medication administration involves many steps and occupies a significant amount of nurses' time. The process of giving medications requires the nurse to have a strong foundation in pharmacology, yet many nursing curricula only provide an introductory course or integrate the information by threading classes of drugs into discussions about specific disorders. This method of instruction leaves many nurses inadequately prepared to handle the vast amount of information required to safely dispense medications.
There are guidelines to help nurses decrease medication errors, such as tall man lettering and accepted abbreviations to minimize dosage mistakes, but there's a need for nurses to know how to prevent metabolic injury to the kidneys, liver, heart, thyroid gland, bone marrow, and muscles through the monitoring of routine lab data. By focusing on lab tests that should be obtained before the beginning of drug therapy and then periodically, the emphasis is shifted away from symptom-triggered monitoring.
Because the kidneys excrete the majority of medications, it's essential that you know the patient's baseline serum creatinine level and glomerular filtration rate (GFR). These are the most accurate indicators of how effectively the kidneys will eliminate compounds contained in a drug. Medications that can cause adverse renal reactions include nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), diuretics, and aldosterone antagonists.
NSAIDs can cause a potentially harmful decrease in renal blood flow, altering glomerular filtration. Now, add a diuretic and an ACE inhibitor or an ARB to the mix and you've got a triple whammy. The combination of an NSAID, ACE inhibitor or ARB, and a diuretic is extremely detrimental in older patients who have declining glomerular filtration associated with aging, or in patients who have preexisting renal disease.
ACE inhibitors and ARBs inhibit efferent arteriolar vasoconstriction in the kidney, and diuretics reduce renal blood flow through the elimination of electrolytes and water. Taking any one of these classes of drugs can impair renal function. That's why it's important to obtain a baseline measurement and note the trends: If the creatinine is rising and the GFR declining, notify the healthcare provider for further evaluation. Some institutions recommend holding an ACE inhibitor when the serum creatinine exceeds 1.4 mg/dL in women and 1.6 mg/dL in men. Other guidelines suggest discontinuing the drug if serum creatinine increases more than 30% within the first 2 months of therapy.
Before administering diuretics, you must also check the patient's levels of potassium, sodium, chloride, magnesium, calcium, and bicarbonate. Additionally, you must be alert for signs of fluid and electrolyte disturbances by monitoring the patient's weight, BP, and pulse and assessing the skin, mucous membranes, and urine output. Be aware that muscle cramps, weakness, lethargy, confusion, and seizures may signal depletion of essential electrolytes.
Aldosterone antagonists, such as spironolactone and eplerenone, cause potassium retention while eliminating sodium and water. Check potassium levels before administering this class of medication and hold the drug if the patient's potassium level is greater than 5 mEq/L. ACE inhibitors and ARBs also cause the renal tubule and collecting ducts to retain potassium by altering aldosterone's action.
Hepatotoxicity is a serious adverse effect that may occur when drugs are metabolized by the liver. When hepatocytes (liver cells) are damaged, one of the first signs of injury is elevated liver function tests (LFTs), particularly the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Reactions develop quickly, and an observant nurse can intervene at the first sign or symptom of liver damage. Dark urine, clay colored stools, and jaundice involving the skin and sclera of the eyes reflect the liver's inability to process bilirubin. Fatigue, abdominal pain, nausea, and loss of appetite may be the initial symptoms that cause the patient to seek medical care. Individuals who have preexisting liver disease, such as viral hepatitis or cirrhosis, are more likely to develop problems when taking a potentially hepatotoxic drug. Because there are so many compounds that are known hepatotoxins, you should recognize which classes of drugs pose a risk, including statins, fibric acid derivatives, and diabetes medications.
Cholesterol-lowering drugs known as statins are one of the most commonly prescribed classes of drugs in the United States. Because their mechanism of action directly involves liver tissue, these compounds can damage liver cells. Atorvastatin causes the greatest effect on lipids, and it's recommended to obtain baseline LFTs before initiating therapy, 12 weeks after beginning therapy, and then semiannually. If ALT or AST increase greater than three times the upper limit of normal, expect a reduction in the dosage or discontinuation of the drug.
Statins can cause muscle inflammation and rhabdomyolysis; at risk for myopathy are petite, older individuals and those with diabetes, liver or renal disease, and uncontrolled hypothyroidism. If muscle pain and weakness occur, creatine kinase (CK) levels must be checked, as well as myoglobin (a protein from muscle cell metabolism). Many drug interactions exist between statins and other commonly prescribed medications, leading to an increase in the circulating levels of statins, which increases the risk of liver damage. But two members of the family, pravastatin and rosuvastatin, pose fewer problems and are less likely to be involved in drug-drug reactions.
LFTs are also recommended for fibric acid derivatives, such as gemfibrozil, fenofibrate, and niacin, which may be prescribed along with the statin family of drugs. The risk of rhabdomyolysis increases when lipid-lowering agents are used in combination. In addition to monitoring AST and ALT, you should be on the lookout for hyperkalemia.
The diabetes drugs pioglitazone and metformin also require monitoring. Pioglitazone may have an effect on liver function; jaundice or ALT greater than three times the upper normal limit warrants discontinuation of this drug. Metformin requires close monitoring of the patient's serum creatinine level because an accumulation of metformin can cause lactic acidosis. This drug is contraindicated when serum creatinine exceeds 1.4 mg/dL in women and 1.5 mg/dL in men. It's also recommended to obtain a baseline and annual complete blood cell (CBC) count and red blood cell indices due to metformin's ability to cause vitamin B12 deficiency with resulting megaloblastic anemia.
Obtaining periodic serum concentrations is required for several classes of drugs, including antiarrhythmics, antiepileptics, atypical antipsychotics, mood stabilizers, and anticoagulants. Because these drugs have a narrow therapeutic index, there's an optimum range in which they're effective. Above the upper limit, the risk of toxicity is high; below the lower limit, effectiveness wanes. Serum concentrations may be drawn randomly or peak and trough levels may be ordered to more accurately assess the drug's distribution in the serum.
Antiarrhythmics are a specialized group of drugs that require close monitoring. Amiodarone is unique due to its excessively long half-life (an average of 58 days). Excretion is primarily via the hepatic and biliary route, and liver function must be monitored to avoid hepatotoxicity. Removal is slow because amiodarone-containing human cells, such as skin cells or cells from the gastrointestinal tract, must be shed for the drug to be eliminated. Thyroid function must be monitored because hypo- or hyperthyroidism can develop while taking this drug. For all antiarrhythmics to function effectively, serum potassium must be normal, and correction of hypo- or hyperkalemia must be done before administration of an antiarrhythmic.
The antiepileptic drug carbamazepine can cause bone marrow suppression. A CBC count must be obtained before initiating therapy, then monthly for 3 months, and then at least every other year. Renal function must be assessed, including urinalysis, blood urea nitrogen, and creatinine, and LFTs obtained because carbamazepine may also cause liver damage. Valproate and topiramate, both antiepileptics, may cause serum ammonia levels to rise; if you observe mental status changes, vomiting, or hypothermia, it's prudent to obtain an ammonia level. Additionally, thrombocytopenia is a risk of valproate use; baseline coagulation tests, including platelets, are recommended.
The risk of hyperglycemia and developing diabetes varies among the atypical antipsychotics. Baseline fasting serum glucose levels should be obtained, then at 4 months and annually. Atypical antipsychotics can increase total cholesterol, low-density lipoprotein cholesterol, and triglycerides, so it's important to obtain a baseline lipid panel and then repeat it at 3 months. Depending on the pattern, lipid levels may be checked periodically or every 2 to 5 years if normal. One member of this class, clozapine, may cause agranulocytosis, a serious hematologic reaction resulting in the production of too few neutrophils. For this reason, monitoring the CBC count and absolute neutrophil count is a standard of practice. To ensure the safety of patients taking clozapine, prescribers are required by the FDA to register with the National Registry, a system that oversees the distribution of this drug and closely monitors lab data to detect the early onset of agranulocytosis.
The mood stabilizer lithium, used primarily in the treatment of bipolar disorder, has a narrow therapeutic range. To avoid toxicity, serum lithium levels must be maintained between 0.6 to 1.2 mEq/L. Recommendations specify twice weekly lab draws until serum concentrations and clinical condition have stabilized, and then every 2 to 6 months depending on symptoms. Because lithium may cause hypothyroidism, thyroid function must be evaluated at the onset of therapy and yearly. Due to lithium's ability to inhibit the action of antidiuretic hormone, water loss with resulting dehydration is a risk for individuals taking diuretics. A periodic basic metabolic panel with attention to sodium and creatinine is imperative. NSAIDs, ACE inhibitors, ARBs, and metronidazole may increase lithium levels, so it's essential to know the signs of lithium excess when you have a patient taking these classes of drugs.
The FDA recommends genotyping for the widely prescribed anticoagulant warfarin because of significant genetic variations in two genes: CYP2C9, which produces an enzyme that metabolizes warfarin, and VKORC1, which codes for an enzyme that regulates vitamin K. International normalized ratio (INR) values must be routinely reviewed. Many individuals are sensitive to the effects of warfarin and may suffer a life-threatening bleeding episode or may continue to form thrombi while taking this anticoagulant. In addition to monthly INR values, genotyping may be added to a baseline evaluation before initiating warfarin therapy.
Monitoring and recognizing abnormal lab values are keys to preventing drug-induced injury. Patient safety is the common denominator, and achieving this goal requires nurses to be knowledgeable about the numerous risks posed by specific classes of drugs. Partnering with the pharmacy department to seek answers to your questions is the best resource that nurses have in the acute care setting. Additionally, there are several web-based resources, including UpToDate, Micromedex, and Epocrates, that provide current information.
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