Relationship of pharmacokinetics to pharmacological response for acetazolamide.

Acetazolamide concentration values derived from a nonlinear model system were related to two pharmacological responses in the rabbit. Kidney response was measured by monitoring urine flow and sodium elimination. Ocular response was followed using an applanation tonometer. Maximum urine flow and sodium elimination occurring immediately after injection correlated with log dose. Urine flow dropped below control values along with a rise in osmolality, suggesting the involvement of antidiuretic hormone. Sodium elimination was correlated with plasma levels. Urine pH is thought to be involved in reducing accessibility of drug to carbonic anhydrase in the kidney. Maximum ocular response also was correlated with log dose. Ocular response was related to a protein fraction, which is believed to be mainly carbonic anhydrase. However, the duration of ocular response was related to the red blood cell protein fraction. Thus, drug activity could conceivably be regulated by monitoring a tissue that is not the site of action and can be sampled readily.