When ingested, absorbed relatively slowly, found in the blood after 30 minutes. With a single dose (in a dose of 1-2 g), the time to reach the maximum concentration in the blood (Tcmax) - 8-12 hours.
Therapeutic concentration in adults is achieved by taking 1 -2 g in 1 day and 0.5-1 g in the following days. Communication with blood proteins - 90-99%.
The drug accumulates in the blood, primarily due to the high degree of binding to blood proteins (90-99%). Well distributed to organs and systems. But unlike other representatives of long-acting sulfanilamides, poorly penetrates the hemato-encephalic barrier (BBB) and its concentration in the cerebrospinal fluid is low. However, with inflammation of the meningeal membranes, the permeability of the BBB sharply increases. It penetrates well into the pleural fluid (60-90% of the concentration in the blood), in the biliary system, where its concentration is 1.5-4 times higher than in the blood.
The preferential metabolism is carried out along the path of microsomal glucuronation, which is associated with cytochrome P450 and NADPH-dependent.
Strong connection with blood plasma proteins and high reabsorption in the tubules of the kidneys (93-97.5%), promotes the slow removal of the drug from the body. The blood contains 5-15% of acetylated metabolites, in urine - 10-25% of acetyl derivatives and 75-90% of glucuronide sulfadimethoxin; the latter is readily soluble and does not provoke the development of crystalluria. The acetyl derivative is not reabsorbed and is completely excreted by the kidneys. After 24 hours, 20-40% of the dose taken out, after 48 hours - up to 56%, after 96 hours - up to 83.3%.