In the glomerulus two factors that will be most critical for the efficiency of removing a drug from the circulation and into the renal tubule are :

1. Hydrophobicity
2. Protein binding
3. Molecular weight
4. Local pH

The correct answer is : 2 and 3

A drug leaving the circulation in the glomerulus and entering the urinary space passes through dedicated fenestrations between endothelial cells, the basal lamina, and the filtration slits between the epithelial cells lining the urinary space. Hence, this is largely a paracellular pathway, similar to ultrafiltration, for which hydrophobicity or pH are less important than molecular weight (and thus protein binding).

 

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