Indian J Physiol Pharmacol 2000; 44 (3) : 323-328

INFLUENCE OF KINNOW JUICE ON THE PHARMACOKINETICS OF SUSTAINED RELEASE THEOPHYLLINE IN HEALTHY MALE VOLUNTEERS

M. C. GUPTA, S. K. GARG* AND V. K. BHARGAVA

Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012

( Received on May 16, 2000)

Abstract: 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 frommm 1-4 hours. The values for all the pharmacokinetic parameters evaluated were on the lower side with kinnow juice except TmRXwhich 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.

Key words: kinnow juice theophylline naringin

INTRODUCTION administered with orange JUIce (12). Inhibition of cytochrome P450 enzymes has Citrus juice of grape fruit has been been considered to be responsible for these reported to increase plasma concentration interactions. Grapefruit juice contains a of several dihydrophyridine calcium channel variety of bioflavonoids (13) and antagonists (1-5) and a number of other furanocoumarins (14). Naringin, its drugs of diverse chemical and aglycome naringenin and bergamottin, a pharmacological characteristics (6-11). furanocoumarin have been shown to be While no such interaction was detected inhibitors of dihydropyridine oxidation (15, when felodipine and nifedipine were co- 16). In addition, naringenin has been

*Corresponding Author 324 Gupta et al Indian J Physiol Pharmacol 2000; 44(3)

reported to be a potent competitive inhibitor METHODS of CYPIA2 mediated demethylatin of caffeine (17). Subjects and study protocol

Recently a new variety of citrus fruit, The study was carried out in ten healthy known as kinnow has been developed male volunteers (Median age 31 years; range in India, which is a hydrid of king between 26 to 42 years) and (Median mandarin and willow leaf mandarin weight-61; range between 57 to 73 Kg). (Citrus nobilis x Citrus deliciosa). Kinnow None of the subjects had any history of drug is one of the most popular citrus fruit of allergy and all were non-alcoholic and non- India because of its superior characteristics smokers. All the subjects underwent clinical like taste, large production potential and examination and hematological and lower price as compared to orange. biochemical tests, which were within normal Currently kinnow is also being exported to limits. A written informed consent was Afganistan, Pakistan and United Kingdom. obtained from all the volunteers and the The major active principles of kinnow juice study protocol was approved by the are limonin and naringin (18), which is also institute's ethics committee. The subjects present in grapefruit juice and have been were asked not to consume any medication considered to be responsible for or citrus fruits or juices for at least 15 days phamacokinetic interactions with number of prior and during the study period. The trial drugs. was conducted in a cross-over randomized design with a two week wash-out period between the treatments. After an overnight Theophylline, one of the principal agents fast, each volunteer received a single oral in long term treatment of chronic asthma dose (300 mg) of sustained release shows concentration dependent effects. theophylline [Tab. Theobid-Okasa Pharma Since theophylline is mainly metabolised Ltd. Dadra (India)) along with 300 ml of by cytochrome P450 isoform lA2 (19), it either water or freshly prepared kinnow may also be a subject to inhibitory effects juice. Food was withheld for next 4 hours of the citrus juice of grapefruit and and no caffeinated beverages or alcoholic kinnow. This food drug interaction has drinks were allowed during the study potential clinical significance because period. 2.0 ml of blood was drawn at 0, 1, 2, citrus juices are often consumed at 4, 6, 9, 12, 24 and 48 hours after the drug breakfast or lunch time when drugs are administration in heparinised tubes. Plasma also taken. The present study was was separated and stored at -20°C until designed to find out whether there is any assayed for theophylline using a PHLC pharmacokinetic interaction of kinnow technique (20). Calibration curves were juice co-administration with sustained prepared with methylaxanthine free human release theophylline in healthy male plasma with known theophylline volunteers. concentrations and were treated in the same Indian J Physiol Pharmacol 2000; 44(3) Kinnow Juice and Theophylline Kinetics .325

way as the samples. Limit of detection was RESULTS 0.2 ug/ml and the intra-assay coefficient of variation was 6.78%. Figure 1 shows the mean theophylline levels at different time points when given Pharmacokinetic analysis with either water or kinnow juice. The plasma concentration of theophylline was The pharmacokinetic data was obtained significantly lower from 1.0 to 4.0 hours using an open one-compartment model after when given with kinnow juice as compared oral administration. Peak plasma to when given with water. Thereafter also, the plasma theophylline levels were lower concentration (Cma) and time to reach peak with kinnow juice but the difference was plasma concentration (Tmax ) were calculated from the observed plasma data of each not statistically significant.

volunteer. Area under the plasma 12 concentration time curve up to the time -- Theophyline period samples were taken (AUC _ ) was O 48 ___ Theophyline + KJ calculated by the trapezoidal rule and 10 AUCt_~ by dividing the last plasma 'p -c 0.05 concentration by the elimination rate E 8 constant (Kel). The sum of AUC and 0. 0-48 -= u AUC4S-~was taken as AUC _. c o 0 .,o 6 s.s, The apparent t1l2e (elimination half life) s:a. 0 Q) was calculated by the formula 0.693/Kel s: f- and Kel was calculated by the least square regression analysis of the monexponential declining plasma concentration time curve. Absorption rate constant (Ka) was calculated by residual method and the absorption half o*---~---'---.----r---~---.--~--~ o 6 12 18 24 30 36 42 48 life (tl12a) was calculated from the formula Time (h) t1/2a = 0.693/Ka.

Fig. 1: Concentration time profile of theophylline Mean residence time (MRT) was (Mean ± SEM) in plasma following oral calculated by the formula MRT = AUMC / administration of 300 mg theophylline with 0- water or kinnow juice in 10 healthy male AUCo_' AUMC being the area under the subjects. moment curve. The results are expressed as Mean ± SEM and paired students 't' Table I shows comparison of test applied for statistical analysis. pharmacokinetic parameters of theophylline P<0.05 was considered to be statistically when given with kinnow juice or water. The significant. peak plasma concentration (Cmax ) was lower 326 Gupta et al Indian J Physiol Pharmacol 2000; 44(3)

TABLE I: Phamacokinetic characteristics of theophylline (Mean ± SEM) following administration of 300 mg theophylline with water or with kinnow juice.

Theophylline kinetics Pharmacokinetic parameters With water With kin now juice

6.6±0.4 Tmaz (h) 5.90±0.43 emu (ug/ml) 9.54±0.85 8.43±0.66 Tlna (h) 2.03±0.52 2.16±0.29

T1I2e (h) (Apparent) 25.13±2.43 21.69±3.08 AUC __ o (ug.g/ml) 372.12±51.26 284.96±21.0 MRT (h) 25.96±1.83 21.94±1.61

MRT-Mean residence time; n = 10 and the time to reach peak plasma Kinnow JUIce (KJ) administration concentration (Tma) was increased with alongwith sustained release theophylline did kinnow juice as compared to water but were not cause and major alteration in most of not statistically different. There was no the pharmacokinetic parameters except for significant difference between absorption a significant lowering in the plasma

(t1l2a) and apparent elimination half life concentration of theophylline at 1, 2 an 4

(t1l2e) between the two groups. Area under hours during the absorption phase. This lack the plasma concentration time curve though of pharmacokinetic interaction in this study decreased in the kinnow juice group, the can be because of several reasons. difference was not statistically significant. Cytochrome isoform CYP1A2 has been No significant difference was observed in shown to be involved in metabolism of the mean residence time (MRT) in the two both theophylline and caffeine, and groups. much higher fraction of caffeine is metabolised as compared to theophylline DISCUSSION (17). So theophylline metabolism would be influenced by kinnow juice to a lesser Recently kinnow juice has been shown extent. Additionally, it has also been to cause an increased concentration of reported that chronic smokers have a two carbamazepine in human volunteers because fold higher CYP1A2 activity than the non- of an inhibitory action on cytochrome smokers (17). All the volunteers in this isoenzyme CYP3A (21). Naringin which is study were non-smokers, so would be likely present in grapefruit juice has been shown to have less CYP1A2 activity and hence less to cause an inhibition of caffeine metabolism volunerable to the effects of kinnow juice. which requires cytochrome isoform CYP1A2 for its metabolism. Kinnow juice also The lower plasma concentration of contains naringin and it was expected to theophylline during the absorption phase cause an inhibition of theophylline only may well be as a result of food drug metabolism. interaction between kinnow juice and Indian J Physiol Pharmacol 2000; 44(3) Kinnow Juice and Theophylline Kinetics 327 theophylline. A decrease in the rate as well Naturally occurring flavonoids present as extent of theophylline absorption from a in vegetables and citrus juices have been sustained release form has ben reported shown to be potent activators of mono- by several workers (22-24). It has also oxygenases in human liver microsomes been reported that food ordinarily slows (29). Flavone, a flavonoid has been reported the rate of absorption of theophylline to stimulate metabolism of zoxazolamine without affecting the extent of absorption both in vitro and in vivo (30). This (25). A diet rich in carbohydrates has been activation process is in contrast to enzyme shown to cause a lowering of plasma inductin is it does not require synthesis theophylline concentration (26). Kinnow of the new enzymatic proteins. KJ also juice with its high carbohydrate content contains several bioflavonoids which may approximately 14 gm/100 gm of kinnow juice cause direct activation of the enzymes. responsible for reduced absorption of Since the changes were limited only to theophylline (27). absorption phase and theophylline is known not to undergo first pass metabolism KJ may cause a delayed Tmax and a in the gut this process of activation lower Cmax along with lower plasma of enzymes may not be of any great concentration during the absorption phase consequence. because of a pH dependent effect also which in turn would affect dissolution The findings of the study show that of the sustained release formulation of kinnow juice can significantly affect the theophylline. An increase in the gastric pH rate of absorption of theophylline from a after food which persisted for a considerable sustained release formulation though it time has earlier been reported in young healthy men and women (28). So kinnow may not affect the extent of absorption. juice with a pH 4-6 (27) could also cause Studies in a larger number of subjects might an increase in pH and thereby a slower throw more light on this potential dissolution of the sustained release interaction. However, it may be advised to formulation as was used in this study. the patients not to consume kinnow juice or other citrus juices at the time theophylline administration. It may also be Tmax is dependent upon the rates of of use to carry out plasma concentration absorption and elimination. Since there was monitoring of theophylline in the patients no significant change in tlh elimination and who routinely consume kinnow juice or MRT of the drug in the body, it would suggest that food ingestion i.e. KJ alongwith citrus juices in their diet. the drug administration slowed the absorption of drug without affecting the ACKNOWLEDGEMENTS elimination of the drug. KJ produced a change in the rate of absorption but not in Authors wish to thank Mr. K. J. Thomas the extent is also evident by the fact that for the technical assistance and also the there was no significant change in AVC in volunteers who consented to participate in the two groups. the study. 328 Gupta et al Indian J Physiol Pharmacol 2000; 44(3)

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