| Salt intake, caffeine, theophylline | |
| 0.8-1.7 mcg/dL | |
| Sulfamethoxazole: interferes with bacterial folic acid synthesis from para-aminobenzoic acid trimethoprim: inhibits dihydrofolic acid reduction to tetrahydrofolate | |
| Amiodarone, disopyramide, dronedarone, procainamide, quinidine, sotalol |