Drugs and the kidney
This article on drug nephrotoxicity is detailed, as it is important to be fully aware of renal side effects of drugs with regard to prevention and early diagnosis in order to manage the condition correctly. Many therapeutic agents are nephrotoxic, particularly when the serum half-life is prolonged and blood levels are raised because of decreased renal excretion. Distal nephrotoxicity is markedly enhanced when the glomerular filtration rate (GFR) is reduced and is a particular threat in elderly patients with so called ‘normal’ creatinine levels. In patients of 45 - 55 years of age the GFR is reduced by about 1 mL/min/year, so that an otherwise healthy person of 80 may have an estimated GFR (eGFR) of <60 mL/min or <50 mL/min, i.e. stage 2, 3 or 3b chronic kidney disease (CKD). Furthermore, other effects related to kidney dysfunction may be seen, e.g. worsening of hypertension with the use of non-steroidal anti inflammatory drugs, increased bruising or bleeding tendency with aspirin, and hyponatraemia hypertension acidosis with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Digoxin is contraindicated in stage 3 CKD, even in a reduced dosage. Other drugs can cause the direct formation of kidney stones, e.g. topiramate (used in the prophylaxis of resistant migraine). Levofloxacin (Tavanic) can cause rupture of the Achilles tendon and other tendons.
Radiocontrast media must be used with care. Occasionally, strategies to prevent acute kidney insufficiency cause irreversible CKD, especially in patients with diabetes and those with myeloma who have stage 4 - 5 CKD. Gadolinium in its many forms (even the newer products) used as contrast medium for magnetic resonance imaging is best avoided in patients with stages 4 and 5 CKD.