The influence of food on the absorption and metabolism of drugs: an update

The effect of food on the pharmacokinetics of Sutetinib maleate capsule, an irreversible EGFR tyrosine kinase inhibitor, in healthy Chinese subjects

Sutetinib is an irreversible inhibitor of epidermal growth factor receptor (EGFR) and showed favorable efficacy and safety in patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) harbouring nondrug-resistant rare EGFR mutations. To evaluate the potential food effect, eighteen healthy Chinese subjects were enrolled in a single-centre, randomized, open-label, two-sequence, two-period crossover study. Sutetinib was administered as a single oral 100 mg under fasting or fed conditions, and pharmacokinetic sampling was performed following each dose and analysed by a validated liquid chromatography/mass spectrometry method. Safety and tolerability were also evaluated. Food intake slightly decreased maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time 0 to infinity (AUC0 - inf) of sutetinib (geometric least-squares mean [GLSM] ratio, 80.94% and 86.11%; 90% confidence interval [CI], 68.43-95.72 and 75.88-97.73) and its active metabolite sutetinib N-Oxide (GLSM ratio, 75.58% and 84.00%; 90% CI, 65.69-86.95 and 75.42-93.56), respectively. In addition, the time to maximum plasma concentration (Tmax) of both sutetinib and its metabolite has been prolonged by 2 h under fed conditions. A total of 31 adverse events (AEs) occurred during the study, with no serious adverse events (SAE) reported, and no obvious difference was observed between the fasting and fed groups. Our results demonstrated that a high-fat and high-calorie diet caused a significant delay in drug absorption and a marginal reduction in drug exposure. Sutetinib was generally well tolerated in healthy Chinese subjects. (This trial was registered at http://www.chinadrugtrials.org.cn . The registration No. is CTR20201933, and the date of registration is 2020-10-16).

Do dietary interventions exert clinically important effects on the bioavailability of β-lactam antibiotics? A systematic review with meta-analyses

BACKGROUND

Managing drug-food interactions may help to achieve the optimal action and safety profile of β-lactam antibiotics.

METHODS

We conducted a systematic review with meta-analyses in adherence to PRISMA guidelines for 32 β-lactams. We included 166 studies assessing the impact of food, beverages, antacids or mineral supplements on the pharmacokinetic (PK) parameters or PK/pharmacodynamic (PK/PD) indices.

RESULTS

Eighteen of 25 β-lactams for which data on food impact were available had clinically important interactions. We observed the highest negative influence of food (AUC or Cmax decreased by >40%) for ampicillin, cefaclor (immediate-release formulations), cefroxadine, cefradine, cloxacillin, oxacillin, penicillin V (liquid formulations and tablets) and sultamicillin, whereas the highest positive influence (AUC or Cmax increased by >45%) for cefditoren pivoxil, cefuroxime and tebipenem pivoxil (extended-release tablets). Significantly lower bioavailability in the presence of antacids or mineral supplements occurred for 4 of 13 analysed β-lactams, with the highest negative impact for cefdinir (with iron salts) and moderate for cefpodoxime proxetil (with antacids). Data on beverage impact were limited to 11 antibiotics. With milk, the extent of absorption was decreased by >40% for cefalexin, cefradine, penicillin G and penicillin V, whereas it was moderately increased for cefuroxime. No significant interaction occurred with cranberry juice for two tested drugs (amoxicillin and cefaclor).

CONCLUSIONS

Factors such as physicochemical features of antibiotics, drug formulation, type of intervention, and patient's health state may influence interactions. Due to the poor actuality and diverse methodology of included studies and unproportionate data availability for individual drugs, we judged the quality of evidence as low.

Drug-food Interactions in the Era of Molecular Big Data, Machine Intelligence, and Personalized Health

The drug-food interaction brings forth changes in the clinical effects of drugs. While favourable interactions bring positive clinical outcomes, unfavourable interactions may lead to toxicity. This article reviews the impact of food intake on drug-food interactions, the clinical effects of drugs, and the effect of drug-food in correlation with diet and precision medicine. Emerging areas in drug-food interactions are the food-genome interface (nutrigenomics) and nutrigenetics. Understanding the molecular basis of food ingredients, including genomic sequencing and pharmacological implications of food molecules, helps to reduce the impact of drug-food interactions. Various strategies are being leveraged to alleviate drug-food interactions; measures including patient engagement, digital health, approaches involving machine intelligence, and big data are a few of them. Furthermore, delineating the molecular communications across dietmicrobiome- drug-food-drug interactions in a pharmacomicrobiome framework may also play a vital role in personalized nutrition. Determining nutrient-gene interactions aids in making nutrition deeply personalized and helps mitigate unwanted drug-food interactions, chronic diseases, and adverse events from their onset. Translational bioinformatics approaches could play an essential role in the next generation of drug-food interaction research. In this landscape review, we discuss important tools, databases, and approaches along with key challenges and opportunities in drug-food interaction and its immediate impact on precision medicine.

Pharmacokinetics and safety of the two oral cefaclor formulations in healthy chinese subjects in the fasting and postprandial states

We conducted a phase I bioequivalence trial in healthy Chinese subjects in the fasting and postprandial states. The goal of this trial was to compare the pharmacokinetics and safety of the test preparation Cefaclor granule (Disha Pharmaceutical Group Co., Ltd.) and the reference preparation Cefaclor suspension (Ceclor®, Eli Lilly and Company). In this trial, 24 subjects were selected in the fasting and postprandial states, respectively. Enrolled subjects randomly accepted a single dose of 0.125 g Cefaclor granule or Cefaclor suspension. The washout period was set as 2 days. Blood samples were collected within 8 h after administration in the fasting state and within 10 h after administration in the postprandial state. Plasma concentrations were determined by Liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters (AUC, Cmax) were used to evaluate bioequivalence of the two drugs. In the fasting trial, the geometric mean ratios (90% confidence intervals CIs) for Cmax, AUC0-t, and AUC0-∞ were 93.01% (85.96%–100.63%), 97.92% (96.49%–99.38%) and 97.95% (96.52%–99.41%), respectively. The GMR (90% CIs) for Cmax, AUC0-t, and AUC0-∞ in postprandial state were 89.27% (81.97%–97.22%), 97.31% (95.98%–98.65%) and 97.31% (95.93%–98.71%), respectively. The 90% CIs of AUC and Cmax in the fasting and postprandial states were within the 80–125% bioequivalence range. Therefore, Cefaclor granule and Cefaclor suspension were bioequivalent and displayed similar safety profiles. Furthermore, food intake affected the pharmacokinetic parameters of both drugs.

Bioequivalence of two esomeprazole magnesium enteric-coated formulations in healthy Chinese subjects

BACKGROUND

The pharmacokinetics and bioequivalence of esomeprazole in healthy Chinese subjects and the effects of food on the pharmacokinetics have not been well studied.

AIM

To evaluate the pharmacokinetic characteristics of esomeprazole magnesium (Eso) enteric- coated capsule in the healthy subjects in China and the bioequivalence of the two formulations.

METHODS

This study was conducted in the Phase I Clinical Trial Unit of the Affiliated Hospital of Changchun University of Chinese Medicine. A total of 64 healthy subjects were enrolled in the study. Thirty-two subjects fasted or fed, took the test or reference formulation Eso enteric-coated capsule by a four-cycle, two-sequence crossover of fasting/fed, self-controlled method. The liquid chromatography-mass spectrometry was performed to determine the drug plasma concentration at 16 different time points within 12 h after drug administration. The pharmacokinetic parameters C_max, area under the curve (AUC)_0-t, and AUC_0-inf were calculated to evaluate the bioequivalence.

RESULTS

Pharmacokinetic parameters were evaluated after subjects took the test formulation and control formulation under fasting status. The ratio of geometric means of C_max was 104.15%, with a confidence interval (CI) of 98.20-110.46%. The ratio of geometric means of AUC_0-t was 105.26%, with a CI of 99.80-111.01%. The ratio of geometric means of AUC_0-inf was 105.37%, with a CI of 99.97-111.06%. The pharmacokinetic parameters were also evaluated after subjects took the reference formulation of Eso enteric-coated capsule after eating. The upper limit of 95% CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state C_max was -0.1689, and the point estimate was 0.9509 (0.80-1.25). The upper limit of 95% CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state AUC_0-t was -0.1015 (≤ 0) , and the point estimate was 0.9003 (0.80-1.25). The upper limit of 95% CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state AUC_0-inf was -0.0593 (≤ 0), and the point estimate was 0.8453 (0.80-1.25). The results indicated that the two formulations were bioequivalent under both fasting and fed states.

CONCLUSION

The two types of esomeprazole tablets were bioequivalent under both fasting and fed states, and both were generally well tolerated.

Diet and Botanical Supplementation: Combination Therapy for Healthspan Improvement?

Healthspan science aims to add healthy, functional years to human life. Many different methods of improving healthspan have been investigated, chiefly focusing on just one aspect of an organism's health such as survival. Studies in Drosophila melanogaster have demonstrated that a reversal to a long-abandoned ancestral diet results in improved functional health, particularly at later ages. Meanwhile, pharmaceutical studies have demonstrated that botanical extracts have potent antiaging properties, capable of extending the mean lifespan of D. melanogaster by up to 25%, without a decrease in early fecundity. In this study, we combine these two different approaches to healthspan extension to examine whether a combination of such treatments results in a synergistic or antagonistic effect on Drosophila healthspan. One botanical extract, derived from Rhodiola rosea, mimicked the effects of the ancestral apple diet with better performance at later ages compared with the control. Another extract, derived from Rosa damascena, decreased age-specific survivorship when combined with the apple diet providing support for the "Poisoned Chalice" hypothesis that combinations of various supplements or diets can elicit adverse physiological responses. More experiments in model organisms should be completed researching the effects of combining healthspan-extending substances in various diet backgrounds.

Identification of beagle food taking patterns and protocol for food effects evaluation on bioavailability

Food is a known primary role to the exposure of the drugs orally administered. Since each animal may have unique food taking pattern and it is difficult to manipulate the food taking to animals, there lacks rationalized protocol for the food effects in pre-clinic study. The objective of this study was to identify the beagle food taking patterns and demonstrate their effects on bioavailability in valsartan. Herein, four types of food taking patterns of beagle were identified via inter-day and intra-day analysis, and named as Persisting, Pulsing, Postponing, Pushing (“4P Modes”), respectively, which were also validated by principal component analysis (PCA). Interestingly, food intake resulted in a reduced area under the concentration-time curve (AUC_0–12h), maximum concentration (C_max) and absorption rate, whilst the reduction varied in “4P Modes” of food taking. General considerations in the design of experiment for food effect to the bioavailability in beagles have been established as: to recognize the food taking patterns in each animal, to confirm the inter-day stability of the food taking behaviors, to trace the food taking patterns in parallel with plasma sampling. In conclusion, the right animals with proper food taking patterns should be assessed and selected for pre-clinic bioavailability evaluations.

Individual differences in timing of peak positive subjective responses to d-amphetamine: Relationship to pharmacokinetics and physiology

Rate of delivery of psychostimulants has been associated with their positive euphoric effects and potential addiction liability. However, information on individual differences in onset of d-amphetamine's effects remains scarce. We examined individual differences in the time to peak subjective and physiological effects and the pharmacokinetics/pharmacodynamics of oral d-amphetamine. We considered two independent studies that used different dosing regimens where subjects completed the drug effects questionnaire at multiple time points post d-amphetamine. Based on the observation of distinct individual differences in time course of drug effects questionnaire "feel", "high", and "like" ratings (DEQH+L+F) in Study 1, subjects in both studies were categorized as early peak responders (peak within 60 minutes), late peak responders (peak > 60 minutes) or nonresponders; 20-25% of participants were categorized as early peak responders, 50-55% as late peak responders and 20-30% as nonresponders. Physiological (both studies) and plasma d-amphetamine (Study 1) were compared among these groups. Early peak responders exhibited an earlier rise in plasma d-amphetamine levels and more sustained elevation in heart rate compared to late peak responders. The present data illustrate the presence of significant individual differences in the temporal pattern of responses to oral d-amphetamine, which may contribute to heightened abuse potential.

Food Does Not Affect the Pharmacokinetics of Tesaglitazar, a Novel Dual Peroxisome Proliferator-Activated Receptor α/γ Agonist

Tesaglitazar is a dual peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonist in development to treat lipid and glucose abnormalities associated with type 2 diabetes. This study evaluated the effects of food on tesaglitazar pharmacokinetics. In an open, randomized, 2-way crossover study, 20 healthy men received tesaglitazar 1 mg during fasting and after a high-fat, high-calorie breakfast. Blood samples were taken to assess pharmacokinetic variables. Systemic exposure to tesaglitazar was unaffected by food intake. Estimated ratios were 0.99 (90% confidence interval [CI], 0.94-1.04) for fed/fasted area under plasma concentration-time curve and 0.82 (90% CI, 0.78-0.86) for fed/fasted maximum plasma concentration (C(max)). Mean C(max) was approximately 18% lower (0.41 [95% CI, 0.38-0.43] versus 0.50 [95% CI, 0.47-0.53] mumol/L), and median time to C(max) was increased (2.00 vs 0.75 h) in fed versus fasted state. The median difference of t(max) was 1.25 h (P = .0001, signed-rank test). Tesaglitazar was well tolerated. Tesaglitazar pharmacokinetics is unaffected by food intake, allowing once-daily administration of tesaglitazar with or without food in clinical practice.

The drugs we have and the drugs we need against major helminth infections

Parasitic worms (helminths) have accompanied humans for thousands of years and, still today, they are pervasive where poverty persists, including large parts of Southeast Asia and the Western Pacific Region. The global strategy for the control of helminth infections is morbidity control and elimination as a public health problem. Regular administration of anthelminthic drugs to at-risk populations (e.g. school-aged children) serves as the backbone of interventions in areas where helminth infections are highly endemic. In this review, we focus on soil-transmitted helminthiasis (ascariasis, hookworm disease, strongyloidiasis and trichuriasis) and food-borne trematodiasis (clonorchiasis, fascioliasis, intestinal fluke infections, opisthorchiasis and paragonimiasis) and discuss the few drugs that are currently available for their treatment and control. Emphasis is placed on efficacy with new light shed on multiple dosing and combination therapy. We summarise recent advances made with anthelminthic drugs that might become the future armentarium for the control of major helminthiasis (e.g. artemisinins, cyclooctadepsipeptides, mefloquine, monepantel, nitazoxandide, synthetic peroxides and tribendimidine). Issuing from our review are current research gaps and the need for concerted efforts to discover, develop and deploy the next generation of anthelminthic drugs.

Effect of food or antacid on pharmacokinetics and pharmacodynamics of febuxostat in healthy subjects

What is already known about this subject. Febuxostat is a novel nonpurine selective inhibitor of xanthine oxidase. What this study adds. This is the first manuscript to address the effect of food and antacid on the pharmacokinetics and/or pharmacodynamics of febuxostat. The study will determine whether the drug can be administered regardless of food or antacid. It will therefore influence how the drug should be administered.

AIMS

To evaluate the effects of food or antacid on the pharmacokinetics and/or pharmacodynamics of febuxostat.

METHODS

Four Phase I, two-period, crossover studies were performed in healthy male and female subjects. Subjects either received single 40-mg (n = 24), multiple 80-mg (n = 24) and single 120-mg (n = 20) doses of febuxostat in fasting and nonfasting conditions, or received single 80-mg (n = 24) doses alone or with antacid.

RESULTS

Food caused a decrease in C(max) (38-49%) and AUC (16-19%) of febuxostat at different dose levels following single or multiple oral dosing with febuxostat. However, a slightly greater percent decrease in serum uric acid concentrations (58% vs. 51%) after multiple dosing with 80 mg of febuxostat under nonfasting conditions was observed, which was statistically (P < 0.05) but not clinically significant. Antacid caused a decrease in C(max) (32%), but had no effect on AUC of febuxostat. Febuxostat was safe and well tolerated in all studies.

CONCLUSIONS

Even though food caused a decrease in the rate and extent of absorption of febuxostat, this decrease was not associated with a clinically significant change in febuxostat pharmacodynamic effect. Despite a decrease in the absorption rate of febuxostat, antacid had no effect on the extent of febuxostat absorption. Therefore, febuxostat can be administered regardless of food or antacid intake.

The effect of food composition on serum testosterone levels after oral administration of Andriol Testocaps

OBJECTIVE

Andriol Testocaps is a new oral formulation of testosterone undecanoate (TU) for treatment of hypogonadism. As TU is taken up by the intestinal lymphatic system, both the presence and the composition of food influence the absorption. The aim of this study was to investigate the effect of food composition on the pharmacokinetics of oral TU.

DESIGN

An open-label, single-centre, four-way crossover study. With a washout period of 6-7 days, 80 mg TU was administered in the morning 5 min after consuming each of four different meals in a randomized order (A: 230 kcal, 0.6 g lipid; B: 220 kcal, 5 g lipid; C: 474 kcal, 19 g lipid; D: 837 kcal, 44 g lipid).

PATIENTS

Twenty-four postmenopausal volunteers.

MEASUREMENTS

Serial blood samples were collected until 24 h after dosing to determine testosterone and dihydrotestosterone (DHT) by gas chromatography-mass spectroscopy (GC-MS).

RESULTS

The bioavailability of testosterone after a low-calorie meal containing 0.6 g lipid or 5 g lipid was relatively low, the area under the concentration-time curve (AUC(0-tlast)) for testosterone being 30.7 and 43.5 nmol h/l, respectively. The bioavailability of testosterone after a meal containing 19 g lipid was considerably higher (AUC(0-tlast) = 146 nmol h/l), whereas increasing the lipid content to 44 g lipid did not further increase the bioavailability of testosterone (AUC(0-tlast) = 154 nmol h/l).

CONCLUSION

Approximately 19 g of lipid per meal efficiently increases absorption of testosterone from oral TU. Therefore, coadministration with a normal rather than a fatty meal is sufficient to increase serum testosterone levels when using oral TU.

Food does not affect the pharmacokinetics of solifenacin, a new muscarinic receptor antagonist: results of a randomized crossover trial

AIM

To determine the effect of food ingestion on the pharmacokinetic profile of solifenacin succinate (YM905; Vesicare, a new bladder selective muscarinic receptor antagonist for the treatment of overactive bladder, a chronic disease usually caused by involuntary detrusor muscle contractions during bladder filling.

METHODS

A randomized, two-period, crossover study in two groups of 12 healthy men (aged 18-45 years, body weight 60-100 kg, body mass index < or =30). A single 10-mg dose of solifenacin was administered to the first group in the fasting state during period 1 and in the fed state during period 2, and to the second group in the fed state during period 1 and in the fasting state during period 2 (10 mg is two times the suggested starting dose). There was a 14-day washout between treatment periods. Parameters obtained included C(max), AUC(last), and AUC(0-inf), as well as t(1/2), t(max), and t(lag).

RESULTS

One subject withdrew during the first period for personal reasons. No statistically or clinically significant pharmacokinetic differences occurred between subjects in the fed and fasting states. All geometric mean ratios were close to 1 (C(max), 1.033; AUC(last), 1.068; AUC(0-inf), 1.040). The 90% confidence intervals (CIs) fell in the predefined no-food-effect boundaries of 0.8-1.25 (C(max), 0.953-1.120; AUC(last), 0.990-1.153; AUC(0-inf), 0.976-1.109). The mean difference in t(1/2) was -3.8 h (90% CI 7.6-0.0). There were no significant differences between the fed and fasting states with regard to t(max) and t(lag) (P > 0.05).

CONCLUSIONS

The pharmacokinetics of oral solifenacin was not affected by food ingestion, suggesting that this drug may be administered with or without food. The results observed in this investigation are consistent with those of previous studies of solifenacin.

Comparative effect of different types of food on the bioavailability of cefaclor extended release tablet

This randomized, six-treatment, six-period, six sequence, single dose, crossover pharmacokinetic study assessed the effect of different types of food on the bioavailability of 500-mg cefaclor extended release tablet in 23 healthy male volunteers. A single dose of cefaclor extended release 500-mg tablet was administered at six occasions: after overnight fasting, after two vegetarian (high-fat and low-fat), two non-vegetarian (high-fat and low-fat) and rice diets. Serial blood samples were collected up to 12 h after dose. Serum cefaclor concentrations were determined by a validated HPLC method. An almost equivalent increase in both Cmax and AUC was observed with both high-fat non-vegetarian and low-fat vegetarian breakfasts. However, when MIC90 values, a pharmacodynamic end-point were compared, the low-fat vegetarian diet fared better than the high-fat non-vegetarian diet. The results obtained favor low-fat vegetarian diet (breakfast) to be taken with cefaclor extended release tablet to achieve maximum benefit in terms of clinical efficacy.

Effect of zobo drink (Hibiscus sabdariffa water extract) on the pharmacokinetics of acetaminophen in human volunteers

Acetaminophen, a common antipyretic-analgesic OTC drug is often administered orally anytime of the day with water or beverages irrespective of possible interactions. Zobo drink, is a sweetened water extract of the dried calyx of Hibiscus Sabdariffa. This work is designed to investigate the effect of zobo drink on an oral dose of acetaminophen. Six healthy male volunteers, ages 28.50 +/- 1.76 years, weighing 62.67 +/- 1.67kg participated in the study. The study was carried out in two phases. In the first phases an oral dose of acetaminophen (1g) was administered to the volunteers and in the second phases, zobo drink was ingested by the volunteers 1.30 h prior the administration of acetaminophen (1g). Acetaminophen concentration in plasma was determined using a validated spectrophotometric method. Pharmacokinetic values obtained were found to be in similar ranges as those previously reported. The absorption parameters t1/2a, Ka, Tmax, Cmax and AUC0-alpha showed no statistically significant changes (p>0.05) after the administration of zobo. There were however statistically significant changes (p<0.05) in Kbeta and t1/2beta of acetaminophen when administered after the zobo drink. This also resulted in 11.69% increase in ClT.

Administration of Indinavir and Low-Dose Ritonavir (800/100 Mg Twice Daily) with Food Reduces Nephrotoxic Peak Plasma Levels of Indinavir

Background

The objective of this study was to compare indinavir peak plasma (Cmax) values after administration of indinavir/ritonavir 800/100 mg on an empty stomach or with food. High indinavir Cmax values have been associated with indinavir-related nephrotoxicity.

Methods

This was an open-label, randomized, two-treatment, two-period, cross-over pharmacokinetic study performed at steady state. HIV-infected patients who had been using indinavir/ritonavir 800/100 mg twice daily for at least 4 weeks were randomized to take this combination with a light breakfast (two filled rolls and 130 ml of fluid) on a first study day, and without food on a second day, or in the reverse order. The pharmacokinetics of indinavir and ritonavir were assessed after plasma and urine sampling during 12 h.

Results

Data for nine patients were evaluated. Administration of indinavir/ritonavir 800/100 mg on an empty stomach resulted in a higher indinavir Cmax [geometric mean (GM) ratio – fasting/fed and 95% confidence interval (CI): 1.28 (1.08–1.52), P=0.01] and a trend to a shorter indinavir tmax ( P=0.07) compared to administration with food. The mode of administration of indinavir/ritonavir did not affect plasma indinavir Cmin and AUC values, parameters that have been associated with the antiviral efficacy of indinavir, nor the urinary excretion of indinavir.

Conclusions

Administration of indinavir/ritonavir 800/100 mg on an empty stomach results in a higher indinavir Cmax compared to ingestion with a light meal. Stated the other way round, intake with a light meal reduces indinavir Cmax, which probably reflects a food-induced delay in the absorption of indinavir. It is recommended to administer indinavir/ritonavir 800/100 mg with food, as a possible means to prevent indinavir-related nephrotoxicity in patients who start or continue with this regimen.

Complete bioavailability and lack of food-effect on pharmacokinetics of gliclazide 30 mg modified release in healthy volunteers

A new modified release (MR) formulation containing 30 mg of gliclazide was developed to obtain a better predictable release of the active principle and to allow once-daily dosing regimen. An absolute bioavailability study was carried out to characterise the performance of the new formulation and the food-effect was also investigated in a separate study. Both studies were single dose, randomised, open label, two way cross over studies with a wash out period between doses. For the bioavailability study, each volunteer received 30 mg of gliclazide given either as a 1 h intravenous infusion or as a 30 mg MR tablet. For the food-effect study, the treatment was given either fasted or 10 min after the start of a standardised Melander breakfast. Blood samples were collected up to 72 h after administrations and plasma samples assayed for gliclazide concentrations using a reverse-phase HPLC method with UV detection. Mean absolute bioavailability of gliclazide was 97% and ranged between 79 and 110% showing complete absorption. A similar moderate to low variability was observed after IV and oral administration showing the MR formulation did not add to the overall variability which is solely due to the disposition parameters, in particular metabolism of gliclazide. No significant difference was observed in t(max), t(1/2z), C(max) and AUC of gliclazide after administration of the 30 mg MR tablet under fasted and fed conditions. In conclusion, after single oral administration of a 30 mg MR tablet, gliclazide was completely absorbed both under fasted and fed conditions. A consistent and optimal release of gliclazide from this formulation leads to a low to moderate overall variability of its pharmacokinetic parameters. Diamicron 30 mg MR can be given without regards to meals i.e. before, during or after breakfast.

Effect of food on the pharmacokinetics of budesonide controlled ileal release capsules in patients with active Crohn's disease

AIM

To study the influence of food on the systemic availability of budesonide in patients with active Crohn's disease.

METHODS

Eight patients with an established diagnosis of Crohn's disease each received 9 mg budesonide controlled ileal release (CIR) capsules (Entocort capsules) orally on two separate occasions: once in a fasting state and once after a heavy breakfast. For reference, deuterium-labelled ((2)H(8)) budesonide, 0.5 mg, was given intravenously. Plasma concentrations of budesonide and (2)H(8)-budesonide were determined for 12 h, and their pharmacokinetic parameters were calculated.

RESULTS

Average systemic availability of budesonide during fasting conditions was 10.7%, area under the curve was 27.5 nmol/L x h and peak plasma concentration was 4.1 nmol/L. Corresponding postprandial values were 13.2%, 27.0 nmol/L x h and 3. 8 nmol/L. Food increased the mean absorption time from 4.5 to 6.8 h (P=0.0012). Body clearance of budesonide was about 25% higher after eating (P=0.0015).

CONCLUSIONS

Food had little influence on systemic availability and peak plasma concentrations of budesonide administered in CIR capsules. Absorption was retarded postprandially, likely due to delayed gastric emptying. Budesonide in CIR capsules can be administered at the same dose regardless of prandial status in patients with Crohn's disease.

The oral route for the administration of cytotoxic drugs: strategies to increase the efficiency and consistency of drug delivery

There is an increasing interest to administer cytotoxic drugs to patients by the oral route. Quality of life issues, treatment advantages and pharmaco-economics are major arguments in favor of oral therapy. However, low or moderate bioavailability in combination with considerable interpatient variability are frequently observed which may reduce the feasibility of the oral route for this class of drugs with a generally narrow therapeutic window. Until recently, investigators focused on absorption enhancers which slightly damage the intestinal surface such as salicylates, methylxanthines and surfactants to improve the oral bioavailability of drugs. To date, a shift can be seen towards more subtle mechanisms to enhance the absorption. This review article focuses on two important mechanisms that determine the oral bioavailability of cytotoxic drugs. These include the presence of drug transporters in the intestinal epithelium pumping drugs into the intestinal lumen, such as MDR1 type P-glycoproteins, and first-pass elimination by cytochrome P450 isoenzymes (e.g. 3A4 and 3A5) or other enzymes in the intestines and/or liver. Currently preclinical and clinical studies are being performed to explore the feasibility of blocking these transporters/enzymes in order to achieve higher and less variable systemic drug levels after oral dosing. This review gives an update of the results of these studies. It is concluded however, that further research to unravel the processes involved in oral drug uptake is warranted to make the oral route a more efficient and consistent way of drug administration.

Drug, meal and formulation interactions influencing drug absorption after oral administration. Clinical implications

Drug-drug, drug-formulation and drug-meal interactions are of clinical concern for orally administered drugs that possess a narrow therapeutic index. This review presents the current status of information regarding interactions which may influence the gastrointestinal (GI) absorption of orally administered drugs. Absorption interactions have been classified on the basis of rate-limiting processes. These processes are put in the context of drug and formulation physicochemical properties and oral input influences on variable GI physiology. Interaction categorisation makes use of a biopharmaceutical classification system based on drug aqueous solubility and membrane permeability and their contributions towards absorption variability. Overlaying this classification it is important to be aware of the effect that the magnitudes of drug dosage and volume of fluid administration can have on interactions involving a solubility rate limits. GI regional differences in membrane permeability are fundamental to the rational development of extended release dosage forms as well as to predicting interaction effects on absorption from immediate release dosage forms. The effect of meals on the regional-dependent intestinal elimination of drugs and their involvement in drug absorption interactions is also discussed. Although the clinical significance of such interactions is certainly dependent on the narrowness of the drug therapeutic index, clinical aspects of absorption delays and therapeutic failures resulting from various interactions are also important.

Lack of effect of food on the oral bioavailability of irbesartan in healthy male volunteers

This study was conducted to evaluate the effects of a high-fat meal on the oral bioavailability of an 300-mg irbesartan tablet in healthy male volunteers. Sixteen healthy young male volunteers participated in this single-center, open-label, single-dose, crossover study. Each volunteer received a single 300-mg irbesartan tablet under fasted conditions and 5 minutes after a high-fat breakfast, with administrations separated by a 7-day washout period. Serial blood samples were collected over a 72-hour period, and plasma samples were analyzed for irbesartan using a validated high-performance liquid chromatography/fluorescence procedure. Food had no statistically significant effects on the peak concentration (Cmax) and area under the concentration-time curve (AUC) of irbesartan. The presence of food was associated with a slightly prolonged time to maximum concentration (tmax) and half-life (t1/2), but the differences were not statistically significant. The results of this study indicate that food does not affect the bioavailability of irbesartan. Thus, irbesartan can be administered without regard to meals.

The use of pharmacoscintigraphy to elucidate food effects observed with a novel protease inhibitor (saquinavir)

PURPOSE

To evaluate mechanistically the effect of food on the absorption and gastrointestinal transit of the protease inhibitor saquinavir.

METHODS

Pharmacoscintigraphic investigation in eight healthy volunteers.

RESULTS

Gastric emptying occurred rapidly in the fasted state with some capsules leaving the stomach prior to disintegration. Unmeasurable plasma concentrations were observed in several subjects when dosed under fasted conditions. Following post-prandial administration the radioactive marker became re-distributed within the stomach contents and consequently slower gastric emptying resulted. Plasma concentrations under fed conditions were measurable up to 12 hrs after administration in seven of the eight subjects. Six of the eight plasma profiles showed secondary peaks at c. 4 hours post-dose; two of which coincided with the gastrocolonic response following ingestion of lunch.

CONCLUSIONS

Bioavailability of saquinavir is significantly improved in the presence of food. Emptying of intact capsules in the fasted state may further reduce bioavailability. In the fed state, capsules disintegrate rapidly and gastric emptying is prolonged which may improve exposure of the drug to target absorption sites. Saquinavir may be absorbed from the colon. Second peaks in the absorption profile can only be attributed to gastrocolonic response following ingestion of a meal in some cases. Increased absorption is more likely to be due to an increase in dissolved drug being available for absorption due to general increased motility and secretion stimulated by ingestion of a meal.

Drug interactions with grapefruit juice

Some drugs demonstrate a significantly greater (up to 3-fold) mean oral bioavailability on coadministration with grapefruit juice. With some calcium antagonists, the benzodiazepines midazolam and triazolam and the antihistamine terfenadine, changes in bioavailability are accompanied by altered drug action. Study design factors possibly contribute to the magnitude of changes in drug bioavailability; they include the source of the citrus, its intake schedule, drug formulations and individual metabolising capacity. The components of citrus juice that are responsible for clinical drug interactions have yet to be fully determined. Based on the flavonoid naringin's unique distribution in the plant kingdom, abundance in grapefruit and ability to inhibit metabolic enzymes, naringin is likely to be one of the grapefruit components influencing drug metabolism. Other components present in citrus fruit, such as furanocoumarins, may be more potent inhibitors than flavonoids and are under investigation. Conclusions drawn from clinical drug interaction studies should be considered specific to the citrus fruit products evaluated because of the variation in their natural product content. The predominant mechanism for enhanced bioavailability is presumably the inhibition of oxidative drug metabolism in the small intestine. The consistent findings across studies of diverse cytochrome P450 (CYP) 3A substrates support the mechanistic hypothesis that 1 or more grapefruit juice components inhibit CYP3A enzymes in the gastrointestinal tract. The evaluation of the need to avoid the concomitant intake of grapefruit products with drugs is best done on an individual drug basis rather than collectively by drug class. Based on the narrow therapeutic range of cyclosporin and research experience in organ transplant recipients, its interaction with grapefruit juice is likely to be clinically significant.