Hyperkalemia in elderly patients receiving standard doses of trimethoprim-sulfamethoxazole

Antimicrobial-associated renal tubular acidosis

OBJECTIVE

To review the literature documenting the association of various antimicrobial medications with the development of renal tubular acidosis (RTA).

DATA SOURCES

A search of the English literature via MEDLINE (1966-November 2003) and International Pharmaceutical Abstracts (1970-November 2003) was conducted to identify human reports of RTA associated with various drugs from all available classes of antimicrobial agents. Major search terms included renal tubular acidosis, acidosis, antibiotics, and antimicrobials. Bibliographies of selected articles were also searched to identify additional reports of RTA.

STUDY SELECTION AND DATA EXTRACTION

Case reports, observational studies, and experimental studies documenting the association of any antimicrobial agent with the development of RTA were included.

DATA SYNTHESIS

Antimicrobial-associated RTA is a relatively uncommon adverse effect, with most reports involving amphotericin B, trimethoprim/sulfamethoxazole, and outdated tetracycline. These agents may induce RTA either through direct tubular toxicity or as a function of their pharmacologic action. The time course for the development of RTA varies depending on the antimicrobial utilized. In most instances, RTA is reversible; however, some patients may experience prolonged recovery after the offending agent is removed.

CONCLUSIONS

Given that antimicrobial-associated RTA is a relatively uncommon adverse effect, review of the patient's drug regimen may reveal these agents as otherwise unrecognized causes of RTA. Likewise, underlying causes of RTA other than medications must be ruled out. Diagnosing antimicrobial-induced RTA may be difficult, given many of these agents may be used in combination and some are intrinsically nephrotoxic.

Trimethoprim-induced hyperkalaemia: clinical data, mechanism, prevention and management

Cotrimoxazole (trimethoprim-sulfamethoxazole) is a combination antimicrobial that is frequently used to treat a wide variety of infections. Only recently has hyperkalaemia been recognised as a relatively common complication of therapy with trimethoprim. Hyperkalaemia has been demonstrated to occur with the administration of both high and standard dosages of trimethoprim. The recognition of this disorder of potassium homeostasis prompted the investigation and ultimate description of the mechanism by which trimethoprim causes hyperkalaemia. Trimethoprim was found to reduce renal potassium excretion through the competitive inhibition of epithelial sodium channels in the distal nephron, in a manner identical to the potassium-sparing diuretic amiloride. Increased risk for hyperkalaemia with trimethoprim treatment appears to be related to both higher dosages and underlying renal impairment. It is probable that other disturbances in potassium homeostasis, such as hyopoaldosteronism and treatment with medications that impair renal potassium excretion, are also risk factors for hyperkalaemia with trimethoprim therapy. Prevention of this adverse reaction depends upon recognition of patients at risk of developing hyperkalaemia as well as proper dosage selection of trimethoprim for the patient's prevailing glomerular filtration rate. Management of hyperkalaemia often mandates discontinuation of the drug, volume repletion with isotonic fluids, and other therapies specific to hyperkalaemia. In circumstances where continued treatment with trimethoprim is required, induction of high urinary flow rates with intravenous fluids and a loop diuretic, as well as alkalinisation of the urine, have been shown to block the antikaliuretic effect of trimethoprim on distal nephron cells.

Hyperkalemia in the elderly: drugs exacerbate impaired potassium homeostasis

OBJECTIVE

To review the pathophysiology underlying the predisposition to hyperkalemia in the elderly; the medications that disrupt potassium balance and promote the development of hyperkalemia in the elderly; the prevention of hyperkalemia in elderly patients treated with potassium-altering medications; and the appropriate management of hyperkalemia when it develops.

METHODS AND MAIN RESULTS

A MEDLINE search of the literature (1966-1996) using the terms hyperkalemia, drugs, elderly, and treatment was conducted and pertinent review articles, textbooks, and personal files were consulted. Elderly subjects appear to be predisposed to the development of hyperkalemia on the basis of both innate disturbances in potassium homeostasis and comorbid disease processes that impair potassium handling. Hyperkalemia in the elderly is most often precipitated by medications that impair cellular uptake or renal disposal of potassium. This electrolyte disorder is best prevented by recognition of at-risk physiology in the aged, avoidance of therapy with certain high-risk medications, and monitoring of plasma potassium concentration and renal function at intervals appropriate for the medication prescribed. Management of hyperkalemia entails identification of the clinical manifestations of severe hyperkalemia, stabilization of cardiac tissue, promotion of cellular potassium uptake, and ultimately removal of potassium from the body.

CONCLUSIONS

Geriatric patients should be considered at risk of developing hyperkalemia, especially when they are prescribed certain medications. Potassium levels should be monitored at appropriate intervals when these patients are treated with potassium-altering medications. Appropriate management of hyperkalemia in the elderly can avoid life-threatening neuromuscular and cardiac complications.

Effect of standard-dose trimethoprim/sulfamethoxazole on the serum potassium concentration in elderly men

OBJECTIVE

To determine the effect of standard-dose trimethoprim/sulfamethoxazole (TMP/SMX) (TMP 160 mg and SMX 800 mg q12h) on the serum potassium concentration.

DESIGN

Retrospective and concurrent study.

SETTING

A Veterans Affairs Medical Center.

PATIENTS

Fifty-three men hospitalized at the Fargo Veterans Affairs Medical Center. Thirty-three patients who received standard-dose TMP/SMX for 3 or more days comprised the study group. Twenty patients who received oral cephradine or amoxicillin for 3 or more days comprised the control group. Patients who received potassium supplements, potassium-sparing diuretics, angiotensin-converting enzyme inhibitors, nonsteroidal antiinflammatory drugs, beta-blockers, heparin, known nephrotoxic agents, patients with a serum creatinine concentration of more than 177 mumol/L, and patients with baseline hyperkalemia (serum potassium concentration > 5.1 mmol/L) were excluded.

RESULTS

The serum potassium concentration in the study group was 4.22 +/- 0.40 mmol/L and increased by 0.31 +/- 0.38 mmol/L at the end of therapy (p < 0.001). Twenty-six patients in the study group (78.8%) had an increase in the serum potassium concentration during TMP/SMX therapy. Fourteen of these patients had follow-up serum potassium concentrations obtained after completion of therapy. The serum potassium concentration returned to baseline in 10 of these patients. The serum creatinine concentration also increased during therapy. However, the correlation between the increase in the serum potassium concentration and the increase in the serum creatinine concentration was weak (Pearson r = 0.29). The serum potassium in the control group was 4.34 mmol/L and remained essentially unchanged during therapy.

CONCLUSIONS

Therapy with standard-dose TMP/SMX is associated with a slight increase in the serum potassium concentration. Routine monitoring of the serum potassium concentration in patients who are treated with standard-dose TMP/SMX therapy is unnecessary. However, TMP/SMX should be considered as a possible cause of unexplained hyperkalemia in elderly patients receiving TMP/SMX therapy.

Case report: severe hyperkalemia in a geriatric patient receiving standard doses of trimethoprim-sulfamethoxazole

A case is reported of a 96-year-old woman with congestive heart failure, hypertension, and chronic obstructive pulmonary disease who presented with altered mental status and severe hyperkalemia, a serum potassium 9.3 meq/L, and electrocardiograph changes. The patient was discharged 1 week prior, with a normal serum potassium, receiving trimethoprim-sulfamethoxazole for urinary tract infection and pneumonia. Serum potassium measurements returned to normal after discontinuation of the drug. Other causes of hyperkalemia were ruled out. Mild hyperkalemia due to trimethoprim-sulfamethoxazole was first reported in 1983 in a 69-year-old woman in whom leukemia with leukopenia developed. In literature to date, mild hyperkalemia in younger geriatric patients has been described. Trimethoprim is thought to act by inhibiting amiloride sensitive sodium channels in the distal nephron and impairing renal potassium secretion in a dose dependent manner. The authors report the case, review the literature, and discuss age-related reduction in renal function as a possible etiology.

Case report: reversible hyperkalemia associated with trimethoprim- sulfamethoxazole

Trimethoprim-sulfamethoxazole (TMP-SMX) is a fixed-dose antimicrobial agent used in a variety of infections. Adverse reactions are more common in patients with AIDS, but occasionally occur in immunocompetent patients. Renal toxicity is usually a hypersensitivity reaction to the sulfa component, and manifests as interstitial nephritis or sulfa crystallization in the renal tubules. Reversible hyperkalemia is a rarely reported side effect of TMP-SMX therapy attributed to TMP inhibition of potassium secretion in the distal renal tubule in a manner similar to the potassium sparing diuretic, amiloride. In this article, the author reports a case of hyperkalemia associated with TMP-SMK occurring in an elderly man with no other risk factors for hyperkalemia, which resolved upon discontinuation of the drug.