We determined the concentrations of
clindamycin and
gentamicin in fluid aspirated from 16
cysts of a surgically excised
polycystic kidney. The patient had received both drugs intravenously for seven days before
nephrectomy. The
cysts were grouped into proximal (pH greater than 6.5) and distal (pH less than 6.5) types according to the pH of the fluid. In nine proximal
cysts the mean concentration of
gentamicin was 1.3 +/- 0.2 and that of
clindamycin was 9.2 +/- 2.3 micrograms/mL. In seven distal
cysts the
gentamicin concentration was 0.7 +/- 0.2 micrograms/mL and the
clindamycin concentration was 34.0 +/- 5.2 micrograms/mL. Plasma
gentamicin was 3.8 (peak) and 1.9 (trough) micrograms/mL, and
clindamycin was 3.9 micrograms/mL (random).
Clindamycin cyst concentrations showed an inverse correlation with cyst fluid pH (r2 = 0.78). These studies confirm that in
autosomal dominant polycystic kidney disease (
ADPKD), certain
cysts develop steep pH gradients between fluid and plasma and indicate that intracystic pH determines the extent to which basic lipophilic
antibiotics accumulate in the fluid.
Lipid-soluble
antibiotics with relatively alkaline pKaS may be useful in the treatment of infected renal
cysts.