RESUMO
The pharmacokinetics of guanfacine (GF, antihypertensive agent with central action) were studied in five patients with renal insufficiency (CCr less than 30 ml/min) after oral administration of a single 4 mg dose. GF was rapidly absorbed, the peak plasma levels (13.28 +/- 1.58 ng/ml) being reached within two hours. The plasma level decreased with a bi-exponential pattern, with a t 1/2 of the beta phase of 24.4 +/- 3.2 h. The plasma clearance was 212 +/- 40 ml/min and the renal clearance 13.9 +/- 5.2 ml/min. The comparison of these results with those observed in hypertensive patients with a normal renal function demonstrates a slower elimination (t 1/2 beta in the reference group of 16.7 h) and a decrease of the total and renal clearances (445 +/- 29 ml/min and 144 +/- 6 ml/min respectively of the reference group) which directly correlated with the decrease of the CCr. The volume of distribution, however, does not seem to be modified. In 5 other patients under chronic dialysis treated with GF for several months, the cumulation was not more improvement than in the chronic renal insufficient group. The dialysis did not appear to interfere with the elimination kinetics of the drug.
