Influence of kinnow juice on the pharmacokinetics of sustained release theophylline in healthy male volunteers.

The effect of kinnow juice on the pharmacokinetics of a single dose of sustained release theophylline was investigated in healthy male volunteers. In a two phased open cross-over randomized study, ten healthy male volunteers were given sustained release theophylline (300 mg) along with 300 ml of water or kinnow juice, a routinely used citrus juice in India. Blood samples were collected at different time points from 0-48 hours. Plasma was assayed for theophylline by a HPLC method and various pharmacokinetic parameters were calculated and compared. The theophylline levels were lower at all the time points with kinnow juice co-administration as compared to water but were significantly so only during the absorption phase from 1-4 hours. The values for all the pharmacokinetic parameters evaluated were on the lower side with kinnow juice except Tmax which was slightly delayed. None of these alterations was found to be significantly different. The results indicate that since there is an interference with the absorption of the drug, the patients may be advised not to consume kinnow juice when taking a slow release theophylline preparation and the monitoring of plasma concentrations of theophylline in patients who routinely consume kinnow juice in their diet might be helpful in better management of these patients.