Effect of Khat chewing on the bioavailability of ampicillin and amoxycillin

Khat, a Cultural Chewing Drug: A Toxicokinetic and Toxicodynamic Summary

Khat (Catha edulis) is a recreational, chewed herbal drug that has been used as a psychostimulant for centuries in East Africa and the Arabian Peninsula, namely in Somalia, Ethiopia, and Yemen. However, the growing worldwide availability of khat has produced widespread concern. The plant comprises a large number of active substances, among which cathinone, cathine, and norephedrine are the main constituents, which can be included in the group of sympathomimetics of natural origin. In fact, these compounds are amphetamine analogues, and, as such, they have amphetamine-like nervous system stimulant effects. Chewing the leaves gives people a sensation of well-being and increases energy, alertness, and self-confidence. The chronic use of khat is, however, associated with severe cardiac, neurological, psychological, and gastrointestinal complications. The psychological dependence and withdrawal symptoms of khat are the reasons for its prolonged use. The aim of this paper is to review current knowledge on the khat plant with toxicokinetic and toxicodynamic perspectives. Namely, this review paper addresses in vitro, in vivo, and human studies. The models used, as well as the concentrations and doses with the respective biological effects, are discussed. Additionally, the main drug interactions involved with khat are described.

The impact of catha edulis (vahl) forssk. ex endl. (celestraceae) (khat) on pharmacokinetics of clinically used drugs

INTRODUCTION

Catha edulis (Vahl) Forssk. ex Endl. (Celestraceae) is used as a recreational drug on daily basis for its euphoric and psychostimulant effects. It is also chewed by individuals who are on medications, raising the possibility of drug-khat interaction. However, limited data are available in the literature, although clinically significant interactions are expected, as khat contains a complex mixture of pharmacologically active constituents.

AREAS COVERED

It provides an overview of the phytochemistry, pharmacokinetics, pharmacodynamics, and pharmacogenetics of khat based on the literature mined from PubMed, Google Scholar, and Cochrane databases. It also presents a detailed account of drug-khat interactions with specific examples and their clinical significance. The interactions mainly occur at the pharmacokinetics level and particular attention is paid for the phases of absorption and cytochrome P450 enzyme-mediated metabolism.

EXPERT OPINION

Despite the increasing trend of khat chewing with medications among the populace and the potential risk for the occurrence of clinically significant interactions, there is paucity of data in the literature demonstrating the magnitude of the risk. The available data, however, clearly demonstrate that the consequence of drug-khat interaction is dependent on genotype. Genotyping, where feasible, could be used to improve clinical outcome and minimize adverse reactions.

Effects of Khat (Catha edulis) use on catalytic activities of major drug-metabolizing cytochrome P450 enzymes and implication of pharmacogenetic variations

In a one-way cross-over study, we investigated the effect of Khat, a natural amphetamine-like psychostimulant plant, on catalytic activities of five major drug-metabolizing cytochrome P450 (CYP) enzymes. After a one-week Khat abstinence, 63 Ethiopian male volunteers were phenotyped using cocktail probe drugs (caffeine, losartan, dextromethorphan, omeprazole). Phenotyping was repeated after a one-week daily use of 400 g fresh Khat leaves. Genotyping for CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A5 were done. Urinary cathinone and phenylpropanolamine, and plasma probe drugs and metabolites concentrations were quantified using LC-MS/MS. Effect of Khat on enzyme activities was evaluated by comparing caffeine/paraxanthine (CYP1A2), losartan/losartan carboxylic acid (CYP2C9), omeprazole/5-hydroxyomeprazole (CYP2C19), dextromethorphan/dextrorphan (CYP2D6) and dextromethorphan/3-methoxymorphinan (CYP3A4) metabolic ratios (MR) before and after Khat use. Wilcoxon-matched-pair-test indicated a significant increase in median CYP2D6 MR (41%, p < 0.0001), and a marginal increase in CYP3A4 and CYP2C19 MR by Khat. Repeated measure ANOVA indicated the impact of CYP1A2 and CYP2C19 genotype on Khat-CYP enzyme interactions. The median MR increased by 35% in CYP1A2*1/*1 (p = 0.07) and by 40% in carriers of defective CYP2C19 alleles (p = 0.03). Urinary log cathinone/phenylpropanolamine ratios significantly correlated with CYP2D6 genotype (p = 0.004) and CYP2D6 MR (P = 0.025). Khat significantly inhibits CYP2D6, marginally inhibits CYP3A4, and genotype-dependently inhibit CYP2C19 and CYP1A2 enzyme activities.

Effect of Khat (Catha edulis) Use on the Bioavailability, Plasma Levels and Antimalarial Activity of Chloroquine

OBJECTIVES

This study aimed to evaluate the effect of khat (Catha edulis) on chloroquine (CQ) bioavailability in healthy Yemeni adults and its effect on CQ plasma levels and parasite clearance among malaria patients.

METHODS

This study took place between January and April 2007 in Bajil and Sana'a, Yemen. Two CQ doses (600 mg each) were given to 15 healthy males on separate occasions; the first dose was followed by a khat-chewing session (phase one) while controls abstained from khat-chewing for the second (phase two). Additionally, 103 patients with Plasmodium falciparum-induced malaria, including both regular khat chewers (n = 57) and non-khat chewers (n = 46), were treated with CQ (25 mg/kg) over three days. Pharmacokinetic parameters were analysed among both controls and malaria patients. Parasite clearance was also investigated for the latter group.

RESULTS

The mean area under the concentration-time curve (AUC) was 2,108.9 versus 2,797.4 ng/hour/mL, mean peak plasma concentration (Cmax) was 415.6 versus 508.7 ng/mL and mean time to reach Cmax was 3.8 versus 3.6 hours for controls in phase one versus phase two, respectively; both AUC and Cmax levels were significantly reduced by khat-chewing (P <0.050). For khat- versus non-khat-chewing malaria patients, mean plasma CQ concentrations were 266.4 ng/mL versus 427.5 ng/mL (P <0.001). Furthermore, CQ was effective in 71.7% and 75.4% of non-khat and khat-chewing malaria patients, respectively (P = 0.823).

CONCLUSION

Khat-chewing was found to significantly reduce plasma CQ levels among healthy volunteers and malaria patients. While receiving CQ treatment, patients should be advised not to chew khat.

The physiological and perceptual effects of plant extracts (Catha Edulis Forsk) during sustained exercise

Background

Khat (Catha Edulis Forsk) is a natural psychoactive substance that contains addictive substances such as Cathine and Cathinone which have similar structure and action to amphetamine. This substance has been suggested that it can decrease perceived exertion and thus improve performance. There is no study in the literature regarding the effect of khat on exercise performance. Therefore, the aim of this study is to find out whether khat leaves can decrease perceived exertion in humans.

Methods

This study is an experimental crossover study conducted at the Substance Abuse Research Centre in Jazan University, Saudi Arabia. Twenty one healthy volunteers were randomly assigned into two experiment trials. Each volunteer visited the lab three times. The first visit was a familiarization session about the nature of the study and the equipment. On the second visit, 45 min before the experiment volunteers ingested either 33 ml of fruit juice (placebo) or the juice mixed with 45 g of ground khat leaves. Then the participants were instructed to perform a 10 Km cycling on an ergometer and recorded the following physiological variables repeatedly on every 5 min of cycling: heart rate, time to complete 10 km cycling, tympanic temperature, and perceived exertion rate. On the third visit a crossover trial was conducted one week after the second visit; then the same cycling test was performed and the same variables were recorded as the second visit. The experimental protocol was reviewed and approved by Research Ethical Committee of the Medical Research Centre, Jazan University.

Results

According to study results, khat dramatically decreased time taken to complete a 10 km cycling time trail (p < 0.05), and significantly increased heart rate (p < 0.05) and tympanic temperature (p < 0.01). However, khat did not reduce participant's perceived exertion during the physical trial. The Bonferrini simultaneous confidence intervals using multivariate Hotelling’s T² was performed to test the significance of the mean vectors for the placebo group and the Khat group and found that groups are statistically significant.

Conclusions

Khat showed a clear enhancing effect on physical performance. The most parsimonious explanation for this effect is that, like the related amphetamines, cathine/cathinone act as stimulants to increase the capacity to perform exercise. Thus, khat produces the same effects which lead to the banning of amphetamine. These findings conform & endorse the recent prohibition of cathinone by the World Anti-Doping Agency (WADA, 2014).

The Psychostimulant Khat (Catha edulis) Inhibits CYP2D6 Enzyme Activity in Humans

The use of khat (Catha edulis) while on medication may alter treatment outcome. In particular, the influence of khat on the metabolic activities of drug-metabolizing enzymes is not known. We performed a comparative 1-way crossover study to evaluate the effect of khat on cytochrome P450 (CYP)2D6 and CYP3A4 enzyme activity. After 1 week of khat abstinence, baseline CYP2D6 and CYP3A4 metabolic activities were determined in 40 Ethiopian male volunteers using 30 mg dextromethorphan (DM) as a probe drug and then repeated after 1 week of daily use of 400 g fresh khat leaves. Urinary concentrations of cathinone and cathine were determined to monitor the subjects' compliance to the study protocol. Genotyping for CYP2D6*3 and CYP2D6*4 was done. Plasma DM, dextrorphan and 3-methoxymorphinan concentrations were quantified. CYP2D6 and CYP3A4 enzyme activities were assessed by comparing plasma log DM/dextrorphan and log DM/methoxymorphinan metabolic ratio (MR) respectively in the presence and absence of khat. Cytochrome 2D6 MR was significantly increased from baseline by concurrent khat use (paired t test, P = 0.003; geometric mean ratio, 1.38; 95% confidence interval [95% CI], 1.12-1.53). Moreover, the inhibition of CYP2D6 activity by khat was more pronounced in CYP2D6*1/*1 compared with CYP2D6*1/*4 genotypes (P = 0.01). A marginal inhibition of CYP3A4 activity in the presence of khat was observed (P = 0.24). The mean percentage increase of CYP2D6 and CYP3A4 MR from baseline by khat use was 46% (95% CI, 20-72) and 31% (95% CI, 8-54), respectively. This is the first report linking khat use with significant inhibition of CYP2D6 metabolic activity in humans.

Drug interactions in African herbal remedies

Herbal usage remains popular as an alternative or complementary form of treatment, especially in Africa. However, the misconception that herbal remedies are safe due to their "natural" origins jeopardizes human safety, as many different interactions can occur with concomitant use with other pharmaceuticals on top of potential inherent toxicity. Cytochrome P450 enzymes are highly polymorphic, and pose a problem for pharmaceutical drug tailoring to meet an individual's specific metabolic activity. The influence of herbal remedies further complicates this. The plants included in this review have been mainly researched for determining their effect on cytochrome P450 enzymes and P-glycoprotein drug transporters. Usage of herbal remedies, such as Hypoxis hemerocallidea, Sutherlandia frutescens and Harpagophytum procumbensis popular in Africa. The literature suggests that there is a potential for drug-herb interactions, which could occur through alterations in metabolism and transportation of drugs. Research has primarily been conducted in vitro, whereas in vivo data are lacking. Research concerning the effect of African herbals on drug metabolism should also be approached, as specific plants are especially popular in conjunction with certain treatments. Although these interactions can be beneficial, the harm they pose is just as great.

Green tea extract weakens the antibacterial effect of amoxicillin in methicillin-resistant Staphylococcus aureus infected mice

Tea (Camellia sinensis) has been known for its modulation of resistance of methicillin-resistant Staphylococcus aureus (MRSA) to beta-lactam antibiotics in vitro. This study aimed to confirm the in vitro effect of green tea extracts with beta-lactams and to determine whether green tea extracts can reduce the minimum inhibitory concentrations (MICs) of amoxicillin in MRSA-infected mice. The catechins in the test tea that account for the reduced resistance to beta-lactams were quantitatively determined by high-performance liquid chromatography. The MICs of the ampicillin, cefazolin, amoxicillin, oxacillin, tea extract alone and tea extract in combination with beta-lactams were determined. Proportions of tea extracts and amoxicillin-tea extract combinations were administered to groups of mice enterally. The in vitro experiment showed that the MICs of four beta-lactams were greatly decreased in the presence of 0.25% tea extract. However, in an in vivo experiment, amoxicillin in combination with 5% tea extract conferred a higher ED(50) than that of antibiotic alone. Green tea extract, alone or in combination with amoxicillin, does not have protective benefits in MRSA-infected mice. This study concluded that tea extract weakened the antibacterial effect of amoxicillin in MRSA infected mice. Tea drinking is not recommended in combination with amoxicillin treatment.

Histopathologic changes in oral mucosa of Yemenis addicted to water-pipe and cigarette smoking in addition to takhzeen al-qat

BACKGROUND

Because the clinicopathologic effects of takhzeen al-qat are similar to those induced by smoking, the aim of this paper was to study the oral effect of 3 bad oral habits: takhzeen al-qat and cigarette and water-pipe smoking.

STUDY DESIGN

This study was done on 33 Yemeni chronic qat users grouped as heavy cigarette smokers (GI), nonsmokers (GII) and water-pipe smokers (GIII). In all cases (n = 33) 2 biopsies were taken (n = 66), one from the buccal mucosa at the chewing side and the other from a similar mucosa at the contralateral (nonexposed) side. Biopsies were prepared for routine H&E staining.

RESULTS

Acanthosis appeared in 88% and 0%, abnormal rete ridges in 70% and 3%, hyperparakeratosis in 67% and 0%, and epithelial dysplasia in 30% and 0% of the chewing and nonchewing sides, respectively, in the 3 groups. Epithelial dysplasia appeared in 41% of GI and GIII (smokers) but in only 9% of GII (nonsmokers).

CONCLUSIONS

Takhzeen al-qat causes distinct histopathologic changes in the oral mucosa at the side of chewing, such as acanthosis, abnormal rete ridges, and hyperparakeratosis. The association between takhzeen al-qat and cigarette or water-pipe smoking may increase the risk of epithelial dysplasia.

Histopathological changes in oral mucosa due to takhzeen al-qat: a study of 70 biopsies

BACKGROUND

Chewing qat leaves (takhzeen al-qat) is a common habit in East Africa and Yemen. It has been reported to cause different systemic effects. At the oral mucosa, it causes clinical changes that appear as white lesions. The aim of this paper was to study the histopathological changes in the oral mucosa related to takhzeen al-qat.

METHOD

Seventy biopsies were studied. Biopsies were divided into three groups: (G1) Forty biopsies were taken from the oral mucosa of the chewing side. (G2) Twenty biopsies were taken from the oral mucosa of the opposite side and (G3) 10 biopsies were taken from the oral mucosa of non-chewing volunteers. All biopsies were conventionally prepared, paraffin embedded and histopathological protocol was followed for each case to study the histopathological changes.

RESULTS

Acanthosis appeared in 97.5% (G1) and 50% (G2), parakeratosis in 45% (G1) and 0% (G2), orthokeratosis in 25% (G1) and 10% (G2), abnormal rete ridges in 97.5% (G1) and 25% (G2), intracellular edema in 80% (G1) and 65% (G2), inflammatory infiltration in the subjacent connective tissue of 55% (G1) and 5% (G2), increased amount of collagenous fibers in 47.5% (G1) and 0% (G2), and mild epithelial dysplasia in 25% (G1) and 0% (G2). Biopsies taken from G3 showed no histopathological changes except one case with intracellular edema. Differences were statistically significant.

CONCLUSION

Takhzeen al-qat caused histopathological changes in the oral mucosa at the side of chewing; however, these changes were innocuous and without any evidence of malignancy.

Herb-drug interactions: an overview of the clinical evidence

Herbal medicines are mixtures of more than one active ingredient. The multitude of pharmacologically active compounds obviously increases the likelihood of interactions taking place. Hence, the likelihood of herb-drug interactions is theoretically higher than drug-drug interactions, if only because synthetic drugs usually contain single chemical entities. Case reports and clinical studies have highlighted the existence of a number of clinically important interactions, although cause-and-effect relationships have not always been established. Herbs and drugs may interact either pharmacokinetically or pharmacodynamically. Through induction of cytochrome P450 enzymes and/or P-glycoprotein, some herbal products (e.g. St John's wort) have been shown to lower the plasma concentration (and/or the pharmacological effect) of a number of conventional drugs, including cyclosporine, indinavir, irinotecan, nevirapine, oral contraceptives and digoxin. The majority of such interactions involves medicines that require regular monitoring of blood levels. To date there is less evidence relating to the pharmacodynamic interaction. However, for many of the interactions discussed here, the understanding of the mechanisms involved is incomplete. Taking herbal agents may represent a potential risk to patients under conventional pharmacotherapy.

Effects of oils and pharmaceutical excipients on the bioavailability of ampicillin orally administered, different oily and aqueous suspensions in rabbit

The in vivo bioavailability and in vitro drug-release studies of ampicillin trihydrate in different oily and aqueous suspensions have been investigated. In addition, partition, solubility, and rheological measurements have also been carried out. The in vivo experimental design was based on a 6 x 6 latin square using the rabbit as the test animal. The bioavailability of ampicillin was determined using the plasma levels, which were measured microbiologically. Results of the study showed that oily and sucrose-containing aqueous formulations enhanced the extent of ampicillin absorption, although not statistically significantly, but was close to the borderline of significance. Ampicillin appears to be absorbed at essentially the same rate from both aqueous and oily formulations. The latter showed plasma-level time curves with biphasic absorption and are likely to produce prolonged plasma concentrations of ampicillin because of the effects of enterohepatic recycling. Viscosity appears to play an insignificant role in the results obtained since the bioavailability parameters correlate poorly with the viscosity except Cmax. It is suggested that enhancement in the bioavailability of ampicillin is due to the decrease in the gut transit rate brought about by the oil which predominates and masks the other effects of viscosity and osmotic effects of sucrose. The existence of a correlation between the in vitro drug-release rate (t50%) and viscosity and the lack of a correlation between in vivo and in vitro parameters support the above suggestion and indicate that traditional dissolution rate tests, such as flask-stirrer method, are unsatisfactory as bioavailability indicators when applied to dosage forms that caused marked changes in physiological factors like GER and biliary excretion.

Herb-drug interactions: review and assessment of report reliability

AIMS

The aim of this systematic review was to assess the published clinical evidence on interactions between herbal and conventional drugs.

METHODS

Four electronic databases were searched for case reports, case series or clinical trials of such interactions. The data were extracted and validated using a scoring system for interaction probability.

RESULTS

One hundred and eight cases of suspected interactions were found. 68.5% were classified as 'unable to be evaluated', 13% as 'well-documented' and 18.5% as 'possible' interactions. Warfarin was the most common drug (18 cases) and St John's wort the most common herb (54 cases) involved.

CONCLUSION

Herb-drug interactions undoubtedly do occur and may put individuals at risk. However our present knowledge is incomplete and more research is urgently needed.

Effect of Maytenus aquifolium extract on the pharmacokinetic and antiinflammatory effectiveness of piroxicam in rats

This study explored the interference by Maytenus aquifolium leaves hydroalcoholic (MALHE) extract, administered orally, on the pharmacokinetic and antiinflammatory activity of piroxicam in rats. The results showed no significant difference in piroxicam bioavailability with simultaneous application of MALHE. MALHE also had no effect on the inhibitory effect of piroxicam on inflammatory processes induced by carrageenan and complete Freund adjuvant.

Socioeconomic and behavioral factors leading to acquired bacterial resistance to antibiotics in developing countries

In developing countries, acquired bacterial resistance to antimicrobial agents is common in isolates from healthy persons and from persons with community-acquired infections. Complex socioeconomic and behavioral factors associated with antibiotic resistance, particularly regarding diarrheal and respiratory pathogens, in developing tropical countries, include misuse of antibiotics by health professionals, unskilled practitioners, and laypersons; poor drug quality; unhygienic conditions accounting for spread of resistant bacteria; and inadequate surveillance.