Steady-state plasma levels and pharmacokinetics of guanfacine in patients with renal insufficiency.

The steady-state pharmacokinetics and renal clearance of guanfacine were studied in patients with renal insufficiency. Apparent total body and renal clearances of guanfacine, as well as apparent volume of distribution, decreased in parallel with the decline in renal function. Higher plasma levels of guanfacine were observed in patients with GFR less than 30 ml/min. The steady state t 1/2 of guanfacine in the presence of renal insufficiency was insignificantly prolonged relative to that observed in the presence of normal renal function and appeared to be independent of the degree of renal insufficiency.