Acute theophylline intoxication. Biphasic first order elimination kinetics in a child.

An acute theophylline intoxication in a child is reported. It was characterized by two distinct first-order elimination processes with t1/2 = 12.6 hr (ke = 0.056 hr-1) and t1/2 = 5.4 hr (ke = 0.128 hr1), respectively. It is proposed that the slower process, which was seen at high plasma levels, represents renal plus saturated hepatic elimination. The later, more rapid process seen at therapeutic plasma levels is consistent with hepatic elimination by biotransformation.