The case:
A 53-year-old man, with a history of DM II, hypertension, depression and hepatitis C, He is admitted for muscle cramps. He has a recent history of epididymitis and is taking 2 antibiotics (he cannot remember the names.) He also takes lisinopril 10 mg daily and fluoxetine 20 mg daily.
| ABG | |
|---|---|
| pH | 7.31 |
| pCO2 | 32 |
| pO2 | 105 |
His EKG showed mildly peaked T waves. He was successfully treated with IV insulin and glucose, albuterol nebulizer and sodium bicarbonate. He also took sodium polystyrene (Kayexalate). On discharge his lab tests:
| Electrolyte panel | |||||
|---|---|---|---|---|---|
| Na | 138 | Cl | 109 | BUN | 19 |
| K | 4.3 | HCO3 | 22 | creat | 1.3 |
| Blood Sugar | 184 |
Speculate on the cause and underlying physiology. We do have a diagnosis.
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Several commentors reasoned that trimethoprim was the culprit. Joel Topf provided an excellent physiology review:
As I recall, we first noticed this phenomenon with high dose sulfamethoxasole-trimethoprim treatment for PCP. More recently, we are diagnosing this problem with normal doses. Generally the patients are either taking an ACE inhibitor, ARB or a potassium sparing diuretic.
Clinical lesson – prior to prescribing this antibiotic, consider other drugs which might lead to this complication.
