Diclofenac sodium: blood concentration of the slow-release form and influence on the metabolism of kallikrein.

The blood concentration of the slow-release formulation of diclofenac sodium (Voltaren) has been determined in 10 patients at various intervals over a period of 22 days. In parallel, the influence of diclofenac on the kallikrein-kinin system was investigated since important interactions between the prostaglandins and kallikrein are known. The peak concentration of the slow-release formulation was significantly decreased compared with data of the standard formulation from other studies and the peak was observed later. The areas under the concentration curves were, however, similar. No signs of drug cumulation were observed during the treatment. The kallikrein concentration decreased after one week in plasma and after two weeks in urine. The plasma concentration of kallikrein reaches control level again after two weeks. Its urine excretion was increased to control levels after the third week. These changes in the kallikrein-kinin system did not reach the level of significance. It is concluded that diclofenac sodium has only a short-term influence on the kallikrein-kinin system.