Influence of Body Fat on the Volume of Distribution of Theophylline

Abstract

Twenty-six acutely bronchospastic patients admitted to the emergency room of an acute care hospital were studied to determine the influence of body fat on the volume of distribution (Vd) of theophylline. Total body weight (TBW), height, skinfold thickness (at three sites), and theophylline levels around an intravenous aminophylline dose were measured. Ideal body weight (IBW), percentage of body fat, and absolute and relative Vd of theophylline were calculated. Vd of theophylline correlated better with IBW than TBW. No relationship was identified between Vd normalized to IBW and either percentage of body fat or the ratio of TBW to IBW. This indicates that in our sample (0.8 IBW less than TBW less than 1.4 IBW), distribution of theophylline into adipose tissue was not an important determinant of Vd. Theophylline's Vd was best estimated by the formula Vd (L) = 0.419(L/kg) X IBW(kg).