Enprofylline, a
drug without
adenosine antagonism and
theophylline, a potent
adenosine antagonist, were compared, double-blind, randomized, in acute
asthma (n = 33). The drugs were given intravenously as loading over 10 min followed by maintenance infusion for 24 h. Mean final plasma levels were very high with
enprofylline (14 mg.l), and larger than calculated with
theophylline (16 mg.l). Seven patients had maximum levels of
enprofylline ranging between 16 and 42 mg.l. Extreme plasma levels of
enprofylline were not associated with any
theophylline-like central nervous system excitatory effects related to seizure-inducing ability. Some irregularities in the heart rhythm did not raise clinical problems and no significant difference between
enprofylline and
theophylline was recorded. At 1 h patients on
enprofylline (mean plasma level: 5.7 mg.l) and
theophylline (12.2 mg.l) had improved their peak expiratory flow rates by 31% and 15% (p less than 0.05), respectively. The improvement in lung function after 24 hours did not differ between treatments suggesting that the high levels of
enprofylline were supramaximal for its anti-
asthma effects in this situation. In conclusion, with
enprofylline it is demonstrated that an
adenosine non-blocking
xanthine derivative may lack CNS-excitatory effects, but be more potent than
theophylline in the treatment of acute
asthma.