[Cross-over double-blind study using neophylline oral (proxyphylline and diprophylline) in bronchial asthma]

In a double-blind crossover trial 16 asthmatic patients were given placebo or 4 or 8 tablets of Neophyllin (each tablet containing 56 mg proxyphylline and 84 mg diprophylline) on two consecutive days. Very slight bronchodilatation independent of the oral dose and plasma level was observed 90 minutes after taking Neophyllin. However, when a betastimulator was inhaled (0.5 mg salbutamol) prior to taking 8 tablets of Neophyllin, surprisingly marked Neophyllin-induced bronchodilatation was observed after 60 and 90 minutes (p less than 0.05 and p less than 0.025). This bronchodilatation was about half that with 4 slow release coated tablets of Neo-Biphyllin (75 mg teophylline in each tablet). When Neophyllin was taken only proxyphylline caused bronchodilatation (no correlation between plasma diprophylline levels and bronchodilatation). The threshold value of plasma proxyphylline was about 13 microgram/ml plasma. Below this level proxyphylline is ineffective (likewise no correlation between plasma proxyphylline levels and bronchodilatation). An oral dose of about 600 mg proxyphylline (in Neophyllin) is needed to reach an effective plasma level within 90 minutes.