Studies on the mechanism of trimethoprim-induced hyperkalemia

Trimethoprim inhibits renal H+-K+-ATPase in states of K+ depletion

There is growing consensus that under physiological conditions, collecting duct H+ secretion is independent of epithelial Na+ channel (ENaC) activity. We have recently shown that the direct ENaC inhibitor benzamil acutely impairs H+ excretion by blocking renal H+-K+-ATPase. However, the question remains whether inhibition of ENaC per se causes alterations in renal H+ excretion. To revisit this question, we studied the effect of the antibiotic trimethoprim (TMP), which is well known to cause K+ retention by direct ENaC inhibition. The acute effect of TMP (5 µg/g body wt) was assessed in bladder-catheterized mice, allowing real-time measurement of urinary pH, electrolyte, and acid excretion. Dietary K+ depletion was used to increase renal H+-K+-ATPase activity. In addition, the effect of TMP was investigated in vitro using pig gastric H+-K+-ATPase-enriched membrane vesicles. TMP acutely increased natriuresis and decreased kaliuresis, confirming its ENaC-inhibiting property. Under control diet conditions, TMP had no effect on urinary pH or acid excretion. Interestingly, K+ depletion unmasked an acute urine alkalizing effect of TMP. This finding was corroborated by in vitro experiments showing that TMP inhibits H+-K+-ATPase activity, albeit at much higher concentrations than benzamil. In conclusion, under control diet conditions, TMP inhibited ENaC function without changing urinary H+ excretion. This finding further supports the hypothesis that the inhibition of ENaC per se does not impair H+ excretion in the collecting duct. Moreover, TMP-induced urinary alkalization in animals fed a low-K+ diet highlights the importance of renal H+-K+-ATPase-mediated H+ secretion in states of K+ depletion.NEW & NOTEWORTHY The antibiotic trimethoprim (TMP) often mediates K+ retention and metabolic acidosis. We suggest a revision of the underlying mechanism that causes metabolic acidosis. Our results indicate that TMP-induced metabolic acidosis is secondary to epithelial Na+ channel-dependent K+ retention. Under control dietary conditions, TMP does not per se inhibit collecting duct H+ secretion. These findings add further argument against a physiologically relevant voltage-dependent mechanism of collecting duct H+ excretion.

Effect of high-dose sulfamethoxazole/trimethoprim and glucocorticoid use on hyperkalemic event: A retrospective observational study

INTRODUCTION

Sulfamethoxazole/trimethoprim causes hyperkalemia; however, the effect of sulfamethoxazole/trimethoprim dose and co-administered glucocorticoids on hyperkalemia has not been clarified.

METHODS

This single-center, retrospective, observational cohort, chart review study involving patients (>20 years) who were treated with sulfamethoxazole/trimethoprim was conducted at Tokyo Women's Medical University, Medical Center East from June 2015 to May 2019. Multivariate Cox proportional hazard model was used to identify risk factors for hyperkalemia (serum potassium level > 5.5 mEq/L). Additionally, Kaplan-Meier curve analyzed the cumulative incidence of hyperkalemia focusing on sulfamethoxazole/trimethoprim dose and concomitant use of glucocorticoids with mineralocorticoid activity.

RESULTS

Among 333 patients, 44 (13%) patients developed hyperkalemia associated with sulfamethoxazole/trimethoprim use for over 49 (interquartile range; 17-233) days. We found associations between the time to hyperkalemia development and sulfamethoxazole/trimethoprim dose (hazard ratio 1.238, 95% confidence interval 1.147-1.338, p < 0.001) and glucocorticoid use (hazard ratio 0.678, 95% confidence interval 0.524-0.877, p = 0.003). Interestingly, the Kaplan-Meier curves revealed that the concomitant use of glucocorticoids did not attenuate the risk of hyperkalemia in patients receiving high-dose sulfamethoxazole/trimethoprim (p = 0.747), whereas concomitant use of glucocorticoids significantly reduced the risk of hyperkalemia in patients receiving non-high dose sulfamethoxazole/trimethoprim (p < 0.001).

CONCLUSIONS

High-dose sulfamethoxazole/trimethoprim is a significant predictor of hyperkalemia. The effect of glucocorticoids on hyperkalemia varies depending on the sulfamethoxazole/trimethoprim dose.

Incidence and Clinical Significance of Hyperkalemia Following Heart Transplantation

BACKGROUND

Hyperkalemia (HK) is a life-threatening complication following solid organ transplantation, and patients often need potassium-chelating agents and deviations from standard posttransplant protocols. This is the first study to report the incidence and clinical impact of hyperkalemia following heart transplantation.

METHODS

We retrospectively included patients who underwent heart transplantation at our institution between April 2014 and December 2018. Patients with multiorgan transplantation were excluded. Clinical outcomes of patients who had serum potassium >5.5 mEq/L in the first year posttransplant (HK group) were compared to patients who did not have serum potassium >5.5 mEq/L in the first year posttransplant (non-HK group).

RESULTS

A total of 143 patients were included in this study. During the first year posttransplant, cumulative incidence of serum potassium >5.0, >5.5, and >6.0 mEq/L was 96%, 63%, and 24%, respectively. Fifty-five percent of patients required treatment with potassium-chelating agents. Sulfamethoxazole-trimethoprim was discontinued because of HK in 39% of patients. Overall survival of patients in the HK group (n = 89) was comparable to that of patients in the non-HK group (n = 54, 91% vs 98% at 1 year, P = .19), whereas infection-free survival was significantly lower in the HK group (34% vs 53% at 1 year, P = .010). Multivariate analysis revealed pretransplant renal dysfunction (odds ratio = 2.62; 95% confidence interval, 1.18-5.80; P = .018) and use of mechanical circulatory support (odds ratio = 2.90; 95% confidence interval, 1.08-7.76; P = .035) as significant predictors of posttransplant hyperkalemia.

CONCLUSIONS

The incidence of HK following heart transplantation was high, with more than half of patients requiring any therapeutic interventions, and HK was related to an increase in infection events.

Evaluation of laboratory disturbance risk when adding low-dose cotrimoxazole for PJP prophylaxis to regimens of high-grade glioma patients taking RAAS inhibitors

BACKGROUND

Cotrimoxazole is associated with the development of hyponatremia, hyperkalemia and elevated serum creatinine, especially when combined with inhibitors of the renin-angiotensin-aldosterone system (RAAS). Pneumocystis jirovecii pneumonia (PJP) prophylaxis is the standard of care for high-grade glioma (HGG) patients receiving temozolomide concurrently with radiotherapy, low-dose cotrimoxazole being the preferred agent. Many of these patients are also taking renin-angiotensin-aldosterone system inhibitors, however the risk of significant laboratory disturbance in these patients remains undescribed.

OBJECTIVE

We evaluated whether high-grade glioma patients taking renin-angiotensin-aldosterone system inhibitors receiving low-dose cotrimoxazole for Pneumocystis jirovecii pneumonia prophylaxis are at additional risk of laboratory disturbances in comparison with their non-renin-angiotensin-aldosterone system counterparts.

METHODS

We conducted a retrospective chart review of adult neuro-oncology patients treated for WHO Grade III or IV glioma between 2013 and 2016. Patient serum Na, K, creatinine, and eGFR were compared (renin-angiotensin-aldosterone system vs. non-renin-angiotensin-aldosterone system) using the chi-square test. Binary logistic regression analysis was then performed to account for differences between cohorts.

RESULTS

Of 63 patients (35 non-renin-angiotensin-aldosterone system, 28 renin-angiotensin-aldosterone system), patients in the renin-angiotensin-aldosterone system cohort were more likely to experience a laboratory disturbance (odds ratio=3.17, p = 0.03). Overall, these disturbances were moderate, but were slightly more common and slightly more severe in the renin-angiotensin-aldosterone system cohort.

CONCLUSION

Adding low-dose cotrimoxazole for Pneumocystis jirovecii pneumonia prophylaxis to the regimens of patients with high-grade glioma taking renin-angiotensin-aldosterone system inhibitors increases the risk of laboratory disturbances. While these are generally moderate, some patients are at risk of significant electrolyte abnormalities requiring intervention.

A physiology-based approach to a patient with hyperkalemic renal tubular acidosis

Hyperkalemic renal tubular acidosis is a non-anion gap metabolic acidosis that invariably indicates an abnormality in potassium, ammonium, and hydrogen ion secretion. In clinical practice, it is usually attributed to real or apparent hypoaldosteronism caused by diseases or drug toxicity. We describe a 54-year-old liver transplant patient that was admitted with flaccid muscle weakness associated with plasma potassium level of 9.25 mEq/L. Additional investigation revealed type 4 renal tubular acidosis and marked hypomagnesemia with high fractional excretion of magnesium. Relevant past medical history included a recent diagnosis of Paracoccidioidomycosis, a systemic fungal infection that is endemic in some parts of South America, and his outpatient medications contained trimethoprim-sulfamethoxazole, tacrolimus, and propranolol. In the present acid-base and electrolyte case study, we discuss a clinical approach for the diagnosis of hyperkalemic renal tubular acidosis and review the pathophysiology of this disorder.

The effect of co-trimoxazole on serum potassium concentration: safety evaluation of a randomized controlled trial

AIMS

Co-trimoxazole maintains a well-established role in the treatment of Pneumocystis jirovecii and Toxoplasma gondii, as well as urinary tract infections. Observational studies report hyperkalaemia to be associated with co-trimoxazole, which may stem from an amiloride-like potassium-sparing effect. The current study investigated changes in serum potassium in patients without acute infections, and the influence of concomitant antikaliuretic drugs on this effect.

METHODS

A post hoc analysis was carried out of a randomized controlled trial in patients with interstitial lung disease who were assigned to placebo or 960 mg co-trimoxazole twice daily. Serum potassium and creatinine were measured at baseline, 6 weeks, and 6, 9 and 12 months. The primary outcome was the difference in mean serum potassium concentrations between co-trimoxazole and placebo at 6 weeks.

RESULTS

Mean serum potassium levels were similar at baseline: 4.24 (± 0.44) mmol l^-1 in the 87 co-trimoxazole group participants and 4.25 (± 0.39) mmol l^-1 in the 83 control participants. Co-trimoxazole significantly increased mean serum potassium levels at 6 weeks, with a difference between means compared with placebo of 0.21 mmol l^-1 [95% confidence interval (CI) 0.09, 0.34; P = 0.001). This significant increase in serum potassium was detectable even after exclusion of patients on antikaliuretic drugs, with a difference between means for co-trimoxazole compared with placebo of 0.23 mmol l^-1 (95% CI 0.09, 0.38; P = 0.002). There were 5/87 (5.7%) patients on co-trimoxazole whose serum potassium concentrations reached ≥5.5 mmol l^-1 during the study period.

CONCLUSIONS

Co-trimoxazole significantly increases serum potassium concentration, even in participants not using antikaliuretic drugs. While the magnitude of increase was often minor, a small proportion in our outpatient cohort developed hyperkalaemia of clinical importance.

Renal Insufficiency in Concert with Renin-angiotensin-aldosterone Inhibition Is a Major Risk Factor for Hyperkalemia Associated with Low-dose Trimethoprim-sulfamethoxazole in Adults

OBJECTIVE

Low-dose trimethoprim-sulfamethoxazole (TMP-SMX) is commonly used to prevent pneumocystis pneumonia in daily practice. Previous reports have shown a relationship between high- or standard-dose of TMP-SMX and hyperkalemia, however it remains unclear whether this is true for low-dose TMP-SMX. In this study we sought to determine the risk factors for hyperkalemia associated with low-dose TMP-SMX.

METHODS

In this retrospective cohort study, 186 consecutive adult patients who received TMP-SMX as prophylaxis for pneumocystis pneumonia from January 2014 to January 2015 were evaluated. Data on the patients' age, gender, baseline estimated glomerular filtration rate (eGFR), baseline serum potassium, maximum serum potassium, duration reaching the maximal serum potassium level, dosage, and concomitant use of angiotensin-converting enzyme inhibitors (ACEi)/angiotensin receptor blockers (ARB), β-blockers, non-steroidal anti-inflammatory drugs and potassium-sparing diuretics were retrospectively collected. Hyperkalemia was defined as a serum potassium level ≥5 mEq/L. Univariate and multivariate analyses were performed.

RESULTS

The median age of the patients was 66 years and 51.1% were men. Hyperkalemia associated with low-dose TMP-SMX was observed in 32 patients (17.2%). The median duration to reach the maximal serum potassium level was 12 days. The multivariate logistic regression analysis identified renal insufficiency to be a major risk factor for hyperkalemia associated with low-dose TMP-SMX (eGFR <60 mL/min/1.73 m(2), adjusted OR 4.62). Moreover, in the subpopulation of patients with renal insufficiency, ACEi/ARB use was considered to be a major risk factor for hyperkalemia (adjusted OR 3.96).

CONCLUSION

Renal insufficiency in concert with ACEi/ARB use is a major risk factor for hyperkalemia induced by low-dose TMP-SMX.

Trimethoprim-sulfamethoxazole and risk of sudden death among patients taking spironolactone

BACKGROUND

Trimethoprim-sulfamethoxazole increases the risk of hyperkalemia when used with spironolactone. We examined whether this drug combination is associated with an increased risk of sudden death, a consequence of severe hyperkalemia.

METHODS

We conducted a population-based nested case-control study involving Ontario residents aged 66 years or older who received spironolactone between Apr. 1, 1994, and Dec. 31, 2011. Within this group, we identified cases as patients who died of sudden death within 14 days after receiving a prescription for trimethoprim-sulfamethoxazole or one of the other study antibiotics (amoxicillin, ciprofloxacin, norfloxacin or nitrofurantoin). For each case, we identified up to 4 controls matched by age and sex. We determined the odds ratio (OR) for the association between sudden death and exposure to each antibiotic relative to amoxicillin, adjusted for predictors of sudden death using a disease risk index.

RESULTS

Of the 11,968 patients who died of sudden death while receiving spironolactone, we identified 328 whose death occurred within 14 days after antibiotic exposure. Compared with amoxicillin, trimethoprim-sulfamethoxazole was associated with a more than twofold increase in the risk of sudden death (adjusted OR 2.46, 95% confidence interval [CI] 1.55-3.90). Ciprofloxacin (adjusted OR 1.55, 95% CI 1.02-2.38) and nitrofurantoin (adjusted OR 1.70, 95% CI 1.03-2.79) were also associated with an increased risk of sudden death, although the risk with nitrofurantoin was not apparent in a sensitivity analysis.

INTERPRETATION

The antibiotic trimethoprim-sulfamethoxazole was associated with an increased risk of sudden death among older patients taking spironolactone. When clinically appropriate, alternative antibiotics should be considered in these patients.

Co-trimoxazole and sudden death in patients receiving inhibitors of renin-angiotensin system: population based study

OBJECTIVE

To determine whether the prescription of co-trimoxazole with an angiotensin converting enzyme inhibitor or angiotensin receptor blocker is associated with sudden death.

DESIGN

Population based nested case-control study.

SETTING

Ontario, Canada, from 1 April 1994 to 1 January 2012.

PARTICIPANTS

Ontario residents aged 66 years or older treated with an angiotensin converting enzyme inhibitor or angiotensin receptor blocker. Cases were those who died suddenly shortly after receiving an outpatient prescription for one of co-trimoxazole, amoxicillin, ciprofloxacin, norfloxacin, or nitrofurantoin. Each case was matched with up to four controls on age, sex, chronic kidney disease, and diabetes.

MAIN OUTCOME MEASURE

Odds ratio for the association between sudden death and exposure to each antibiotic relative to amoxicillin, after adjustment for predictors of sudden death according to a disease risk index.

RESULTS

Of 39,879 sudden deaths, 1027 occurred within seven days of exposure to an antibiotic and were matched to 3733 controls. Relative to amoxicillin, co-trimoxazole was associated with an increased risk of sudden death (adjusted odds ratio 1.38, 95% confidence interval 1.09 to 1.76). The risk was marginally higher at 14 days (adjusted odds ratio 1.54, 1.29 to 1.84). This corresponds to approximately three sudden deaths within 14 days per 1000 co-trimoxazole prescriptions. Ciprofloxacin (a known cause of QT interval prolongation) was also associated with an increased risk of sudden death (adjusted odds ratio 1.29, 1.03 to 1.62), but no such risk was observed with nitrofurantoin or norfloxacin.

CONCLUSIONS

In older patients receiving angiotensin converting enzyme inhibitors or angiotensin receptor blockers, co-trimoxazole is associated with an increased risk of sudden death. Unrecognized severe hyperkalemia may underlie this finding. When appropriate, alternative antibiotics should be considered in such patients.

Trimethoprim-induced hyperkalemia in burn patients treated with intravenous or oral trimethoprim sulfamethoxazole for methicillin-resistant Staphylococcus aureus and other infections: nature or nurture?

Trimethoprim is well known to cause rashes; however, what is not commonly known is that it causes sudden and profound hyperkalemia in 10 to 20% of treated patients. The uniqueness of burn patients begs the question whether changes known to occur in these patients might also increase this trimethoprim effect. After institutional review board approval, a retrospective study evaluated 224 patients with thermal injury who had been treated with trimethoprim sulfamethoxazole (TMP-SMX), 24 of whom had underlying renal impairment (creatinine clearances <50 ml/min) and were excluded, leaving 200 patients for analysis. Three definitions of drug-induced hyperkalemia were used: 1) a ≥ 1 mEq/L rise, 2) a >0.8 mEq rise in potassium in <24 hours warranting early discontinuation of TMP-SMX, and 3) "marked" hyperkalemia defined as serum potassium of ≥ 5.5 mEq/L within 48 hours. A potassium level before trimethoprim exposure (TxK) and after TxK were collected retrospectively. Demographic data were analyzed with Student's t-test and trimethoprim dose alone, demonstrating a significant difference. Analysis of 200 patients exposed to trimethoprim demonstrated an elevation of potassium (first definition) in 31 patients (15.5%), a rapid change in serum potassium in two patients (second definition), and marked hyperkalemia (>5.5 mEq/L) in 13 patients (6.5%). Hyperkalemia never occurred in 166 of 200 patients (82%; before TxK, 3.9 ± 0.4; after TxK, 4.3 ± 0.5 mEq/L). Change in serum potassium among patients with hyperkalemia was 4.0 ± 0.5 mEq/L before TxK and 5.3 ± 0.7 mEq/L after TxK. Twelve published hyperkalemia risk factors were reviewed in these 200 patients and only history of hypertension and need for intubation was more common in those with hyperkalemia. A nearly 20% incidence of hyperkalemia and 6% serious hyperkalemia in burn patients is consistent with reports in patients without burn injury. These data also suggest that the metabolic and hormonal changes associated with burn injury do not increase further the genetically predisposed hyperkalemia resulting from exposure to trimethoprim. These data suggest patients treated with TMP-SMX should have routine serum potassium monitoring before discharge.

Trimethoprim-sulfamethoxazole induced hyperkalaemia in elderly patients receiving spironolactone: nested case-control study

OBJECTIVES

To characterise the risk of admission to hospital for hyperkalaemia in elderly patients treated with trimethoprim-sulfamethoxazole in combination with spironolactone.

DESIGN

Population based nested case-control study.

SETTING

Ontario, Canada, from 1 April 1992 to 1 March 2010.

PARTICIPANTS

Cases were residents of Ontario aged 66 years or above receiving chronic treatment with spironolactone and admitted to hospital with hyperkalaemia within 14 days of receiving a prescription for either trimethoprim-sulfamethoxazole, amoxicillin, norfloxacin, or nitrofurantoin. Up to four controls for each case were identified from the same cohort, matched on age, sex, and presence or absence of chronic kidney disease and diabetes, and required to have received one of the study antibiotics within 14 days before the case's index date.

MAIN OUTCOME MEASURES

Odds ratio for association between admission to hospital with hyperkalaemia and receipt of a study antibiotic in the preceding 14 days, adjusted for conditions and drugs that may influence risk of hyperkalaemia.

RESULTS

During the 18 year study period, 6903 admissions for hyperkalaemia were identified, 306 of which occurred within 14 days of antibiotic use. Of these, 248 (81%) cases were matched to 783 controls. 10.8% (17,859/165,754) of spironolactone users received at least one prescription for trimethoprim-sulfamethoxazole. Compared with amoxicillin, prescription of trimethoprim-sulfamethoxazole was associated with a marked increase in the risk of admission to hospital for hyperkalaemia (adjusted odds ratio 12.4, 95% confidence interval 7.1 to 21.6). The population attributable fraction was 59.7%, suggesting that approximately 60% of all cases of hyperkalaemia in older patients taking spironolactone and treated with an antibiotic for a urinary tract infection could be avoided if trimethoprim-sulfamethoxazole was not prescribed. Treatment with nitrofurantoin was also associated with an increase in the risk of hyperkalaemia (adjusted odds ratio 2.4, 1.3 to 4.6), but no such risk was found with norfloxacin (adjusted odds ratio 1.6, 0.8 to 3.4)

CONCLUSIONS

Among older patients receiving spironolactone, treatment with trimethoprim-sulfamethoxazole was associated with a major increase in the risk of admission to hospital for hyperkalaemia. This drug combination should be avoided when possible.

Severe hyperkalemic type 4 renal tubular acidosis after kidney transplantation: a case report

BACKGROUND

Hyperkalemia after transplantation is a common event, occurring in up to 70% of patients. It is usually asymptomatic but sometimes manifests as muscle weakness or cardiac arrhythmias.

METHODS

Case report.

RESULTS

At 102 days after a second cadaveric kidney transplantation, a 15-year-old boy, was admitted to the emergency room with severe muscle weakness. His examinations showed a serum potassium of 9.8 mEq/L; blood pH 7.1; serum bicarbonate 7.6 mmol/L; and creatinine 2.5 mg/dL. He was initially treated with sodium bicarbonate, calcium gluconate, and furosemide. Subsequent investigation showed hyperchloremic metabolic acidosis, urinary pH <5.5, positive urinary anion gap, reduced transtubular potassium gradient (TTKG, 1.5) and low levels of aldosterone (0.7 ng/mL), suggesting the presence of type 4 renal tubular acidosis (RTA). Other causes of hyperkalemia were excluded in the present case. Serum levels of potassium returned to normal when fludrocortisone was added to the bicarbonate supplementation. This case of severe hyperkalemic secondary to type 4 RTA after kidney transplantation only responded to the combination of alkali and mineralocorticoid therapies.

Aldosterone antagonists in the treatment of heart failure

PURPOSE

The clinical benefits, adverse effects, pharmacokinetics, and recommendations for the appropriate use of the aldosterone antagonists spironolactone and eplerenone in patients with heart failure are reviewed.

SUMMARY

Heart failure is a clinical syndrome characterized by the functional inability of the ventricle to meet the metabolic demands of the body. Renal hypoperfusion occurs as a result of reduced cardiac output, resulting in the activation of the renin-angiotensin-aldosterone system, which compensates for the hypoperfusion. However, this contributes to the pathology of the disease by, among other actions, increasing the release of aldosterone. Aldosterone has been shown to cause coronary inflammation, cardiac hypertrophy, myocardial fibrosis, ventricular arrhythmias, and ischemic and necrotic lesions. There are currently two aldosterone antagonists commercially available in the United States, spironolactone and eplerenone. Spironolactone is a nonselective aldosterone antagonist, and eplerenone is selective to the aldosterone receptor. Although numerous clinical trials have evaluated the efficacy of each drug, no studies have directly compared spironolactone and eplerenone. Both have been shown to improve morbidity and mortality in patients with advanced heart failure. Adverse effects of both spironolactone and eplerenone include potentially life-threatening hyperkalemia, which can be induced by renal insufficiency, diabetes mellitus, advanced heart failure, advanced age, and concurrent drug therapy.

CONCLUSION

Spironolactone and eplerenone are life-saving agents in patients with advanced heart failure and may benefit patients with mild heart failure. Potassium and renal function must be routinely assessed to minimize the risk of life-threatening hyperkalemia.

Effect of trimethoprim-sulfamethoxazole on Na and K+ transport properties in the rabbit cortical collecting duct perfused in vitro

BACKGROUND

In this study, the membrane mechanisms of hyperkalemia caused by trimethoprim-sulfamethoxazole (TMP-SMX) combination antibiotics were assessed in the cortical collecting duct (CCD).

METHODS

We used the microelectrode technique and flux measurements, and examined the effects of TMP and SMX on electrical properties of the apical and basolateral membranes in the rabbit CCD perfused in vitro.

RESULTS

TMP in the lumen caused increases in apical membrane voltage, fractional apical membrane resistance (fRA), and transepithelial resistance (RT), all effects which were completely inhibited by luminal amiloride, but not by luminal Ba2+. The luminal TMP inhibited both net Na+ reabsorption and K+ secretion in the CCD. TMP in the bath slightly but significantly depolarized transepithelial voltage and basolateral membrane voltage without influencing fRA or RT. SMX in the lumen or bath had no effect on barrier voltages or resistances.

CONCLUSION

TMP mainly acts on the apical membrane of the CCD, inhibits the amiloride-sensitive macroscopic Na+ conductance in this membrane, and thereby decreases the net driving force for K+ exit across the membrane, resulting in an inhibition of K+ secretion. SMX in the lumen or bath had no effect on the CCD.

Severe hyperkalemia in two renal transplant recipients treated with standard dose of trimethoprim-sulfamethoxazole

Hyperkalemia is a serious electrolyte disorder and is a frequent finding in renal transplant recipients. Trimethoprim-induced hyperkalemia has been increasingly reported in recent years. We describe two renal transplant recipients who developed end-stage renal disease secondary to familial Mediterranean fever and presented with severe hyperkalemia secondary to the use of standard dose of trimethoprim. One of the patients had potential underlying adrenal insufficiency, which might be a contributing factor for the development of hyperkalemia. We concluded that renal transplant patients receiving even the standard dose of trimethoprim should be monitored closely for the development of hyperkalemia. They should be recognized as a group with increased risk in regard to their concurrent renal insufficiency, concomitant use of cyclosporine, and associated tubulointerstitial disease. Patients with secondary amyloidosis are at even greater risk, and subclinical adrenal insufficiency may be an underlying risk factor for the development of severe, life-threatening hyperkalemia among this group of patients.

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.

Effect of trimethoprim on the renal clearance of lamivudine in rats

Lamivudine undergoes minimal metabolism and renal clearance of the unchanged drug is the predominant mechanism of clearance. The effect of trimethoprim on the renal clearance of lamivudine was investigated in rats in-vivo. Total renal clearance of lamivudine was about three times higher than the glomerular filtration rate in rats receiving an infusion of tritium-labelled lamivudine. Concomitant infusion of trimethoprim reduced the renal clearance of lamivudine to about half, but did not affect the level of radioactivity in the renal cortex. When rats received an infusion of lamivudine with probenecid, cimetidine or quinidine, the renal clearance of lamivudine was only significantly reduced by co-administration of cimetidine. These findings suggest that secretion in the renal proximal tubule takes an active part in the total renal clearance of lamivudine, and that cationic drugs such as trimethoprim and cimetidine may inhibit the secretion of lamivudine without greatly affecting the concentration of lamivudine in the renal cortex.