One of the following diuretics does not require its presence in the tubular lumen for its pharmacological effects :

Most of the diuretics act from the luminal side of the membrane in the nephron. Thiazides, loop diuretics, carbonic anhydrase inhibitors and epithelial Na+channel blockers (e.g. amiloride and triamterene) are secreted in the proximal tubules through organic anion/cation transport process. Osmotic diuretics reach the lumen of proximal tubules via glomerular filtration. Aldosterone antagonists like spironolactone do not act through luminal side rather they act from basolateral side of the membrane. Therefore, these agents do not require access to the tubular lumen.