Krabinex Mechanism of Action

Pharmacology: The exact mechanism of action of Hydroxyurea has not been fully elucidated. However, it has been reported that the drug is cell cycle specific and acts on the S phase where concentrations of the enzyme, ribonucleoside diphosphate reductase which catalyzes the reductive conversion of ribonucleotide to deoxyribonucleotide (an important step in the biosynthesis of DNA) are greater. Reports have shown that Hydroxyurea interferes with the synthesis of DNA without interfering with the synthesis of RNA or protein. Although Hydroxyurea may have multiple sites of action, it appears likely that the drug inhibits the incorporation of thymidine into DNA in addition to directly damaging the DNA. Hydroxyurea can also destroy the tyrosyl free radical that is formed as the catalytic center of ribonucleoside diphosphate reductase.
Pharmacokinetics: Following oral administration, Hydroxyurea undergoes absorption readily in the GIT and attains its peak CSF concentrations within 3 hours. Hydroxyurea can also cross the blood-brain barrier. Half of an orally administered dose is degraded in the liver and is excreted in urine as urea and unchanged drug. Some are excreted as respiratory carbon dioxide via the lungs. Blood concentrations decline rapidly and there is no cumulative effect with repeated administration. For this reason, higher blood concentrations are attained if the regular dosage is given in a large, single oral dose than if it is administered in divided doses.
Carcinogenicity, Mutagenicity and Impairment of Fertility: Drugs, which affect DNA synthesis, e.g. Hydroxyurea, may be potential mutagenic agents. The physician should carefully consider this possibility before administering this drug to male or female patients who contemplate conception.