What medications are known to cause renal tubular acidosis?

Medications Causing Renal Tubular Acidosis

The most clinically significant drugs causing renal tubular acidosis (RTA) are chemotherapeutic agents (cisplatin, ifosfamide, pemetrexed), amphotericin B, trimethoprim-sulfamethoxazole, carbonic anhydrase inhibitors (topiramate, zonisamide), and aldosterone antagonists (spironolactone). 1, 2

Chemotherapeutic Agents

Platinum-based chemotherapy and alkylating agents are the most nephrotoxic anticancer drugs causing proximal RTA (Type 2):

• Cisplatin causes proximal tubulopathy with Fanconi syndrome, characterized by sodium and magnesium wasting, nephrogenic diabetes insipidus, and metabolic acidosis through direct tubular injury and acute tubular necrosis 1, 3

• Ifosfamide produces acute tubular injury leading to proximal RTA, Fanconi syndrome, and nephrogenic diabetes insipidus through metabolism into chloroacetaldehyde and other toxic metabolites in the proximal tubule 1, 3

• Pemetrexed causes similar proximal tubular dysfunction with Fanconi syndrome and nephrogenic diabetes insipidus through inhibition of dihydrofolate reductase and other folate-dependent enzymes 1

• Streptozocin produces dose-related nephrotoxicity manifesting as hypophosphataemia, hypokalaemia, hypouricaemia, renal tubular acidosis, glucosuria, and aminoaciduria 4

Antimicrobial Agents

Amphotericin B and trimethoprim-sulfamethoxazole are the most common antimicrobial causes of RTA:

• Amphotericin B (particularly deoxycholate formulation) causes distal RTA (Type 1) with urinary potassium and magnesium wasting, bicarbonaturia, and renal tubular acidosis in up to 80% of treated patients through direct tubular toxicity 5, 6, 2

• Trimethoprim-sulfamethoxazole causes Type 4 (hyperkalemic) RTA by blocking epithelial sodium channels in the collecting duct, mimicking aldosterone deficiency 5, 2, 7

• Foscarnet causes electrolyte abnormalities including hypocalcemia, hypophosphatemia, hyperphosphatemia, hypomagnesemia, and hypokalemia that can contribute to RTA 5

• Cidofovir produces dose-dependent proximal tubular toxicity with glycosuria, bicarbonaturia, phosphaturia, and polyuria 5

Anticonvulsants and Carbonic Anhydrase Inhibitors

Carbonic anhydrase inhibitors cause proximal RTA (Type 2) through impaired bicarbonate reabsorption:

• Zonisamide causes distal RTA with metabolic acidosis and episodic hypokalemia, which resolves upon drug discontinuation 8

• Topiramate and other carbonic anhydrase inhibitors impair proximal tubular bicarbonate reabsorption 2, 9

Diuretics and Aldosterone Antagonists

Potassium-sparing diuretics cause Type 4 (hyperkalemic) RTA:

• Spironolactone causes Type 4 RTA with severe hyperkalemia and metabolic acidosis, particularly in elderly patients with underlying renal impairment, through aldosterone receptor blockade 10, 9

• Heparin (including low molecular weight heparin) causes Type 4 RTA by suppressing aldosterone synthesis, leading to hyperkalemia and hyperchloremic metabolic acidosis 11

Antiretroviral Agents

Tenofovir causes proximal tubular dysfunction:

• Tenofovir produces proximal renal tubular dysfunction with Fanconi syndrome, though the mechanism involves mitochondrial toxicity rather than direct RTA in most cases 5

Clinical Recognition and Monitoring

Key diagnostic features to identify drug-induced RTA:

• Hyperchloremic metabolic acidosis with normal anion gap is the hallmark finding across all RTA types 12, 9

• Urine pH >5.5 in the presence of systemic acidosis indicates distal RTA (Type 1), while urine pH <5.5 suggests proximal RTA (Type 2) or Type 4 RTA 12, 13

• Hypokalemia occurs with Types 1 and 2 RTA (cisplatin, ifosfamide, amphotericin B), while hyperkalemia characterizes Type 4 RTA (trimethoprim-sulfamethoxazole, spironolactone, heparin) 1, 2, 9

• Electrolyte supplementation guided by serum biochemistry is strongly recommended when persistent electrolyte imbalance is detected in cancer survivors with tubular dysfunction 3

Management Approach

Immediate actions upon suspecting drug-induced RTA:

• Discontinue the offending agent when clinically feasible, as most drug-induced RTA is reversible upon cessation 2, 8, 7

• Monitor serum electrolytes, blood gases, and renal function closely in patients receiving known nephrotoxic medications with narrow therapeutic windows 14

• Provide alkali therapy (sodium bicarbonate or citrate) for symptomatic acidosis, particularly in Types 1 and 2 RTA 12, 9

• Correct electrolyte abnormalities with potassium supplementation for hypokalemic forms or potassium restriction/binders for hyperkalemic Type 4 RTA 3, 9