Effect of food on the bioavailability of stavudine in subjects with human immunodeficiency virus infection

Chemometrics as a valuable tool for evaluating interactions between antiretroviral drugs and food

AIMS

Clinically significant interactions with food occur for more than half of antiretroviral drugs. Different physiochemical properties deriving from the chemical structures of antiretroviral drugs may contribute to the variable food effect. Chemometric methods allow analysing a large number of interrelated variables concomitantly and visualizing correlations between them. We used a chemometric approach to determine the types of correlations among different features of antiretroviral drugs and food that may influence interactions.

METHODS

Thirty-three antiretroviral drugs were analysed: ten nucleoside reverse transcriptase inhibitors, six non-nucleoside reverse transcriptase inhibitors, five integrase strand transfer inhibitors, ten protease inhibitors, one fusion inhibitor and one HIV maturation inhibitor. Input data for the analysis were collected from already published clinical studies, chemical records and calculations. We constructed a hierarchical partial least squares (PLS) model with three response parameters: postprandial change of time to reach maximum drug concentration (ΔTmax ), albumin binding (%) and logarithm of partition coefficient (logP). Predictor parameters were the first two principal components of principal component analysis (PCA) models for six groups of molecular descriptors.

RESULTS

PCA models explained 64.4% to 83.4% of the variance of the original parameters (average: 76.9%), whereas the PLS model had four significant components and explained 86.2% and 71.4% of the variance in the sets of predictor and response parameters, respectively. We observed 58 significant correlations between ΔTmax , albumin binding (%), logP and constitutional, topological, hydrogen bonding and charge-based molecular descriptors.

CONCLUSIONS

Chemometrics is a useful and valuable tool for analysing interactions between antiretroviral drugs and food.

Interactions of Antiretroviral Drugs with Food, Beverages, Dietary Supplements, and Alcohol: A Systematic Review and Meta-analyses

Multiple factors may affect combined antiretroviral therapy (cART). We investigated the impact of food, beverages, dietary supplements, and alcohol on the pharmacokinetic and pharmacodynamic parameters of 33 antiretroviral drugs. Systematic review in adherence to PRISMA guidelines was performed, with 109 reports of 120 studies included. For each drug, meta-analyses or qualitative analyses were conducted. We have found clinically significant interactions with food for more than half of antiretroviral agents. The following drugs should be taken with or immediately after the meal: tenofovir disoproxil, etravirine, rilpivirine, dolutegravir, elvitegravir, atazanavir, darunavir, lopinavir, nelfinavir, ritonavir, saquinavir. Didanosine, zalcitabine, zidovudine, efavirenz, amprenavir, fosamprenavir, and indinavir should be taken on an empty stomach for maximum patient benefit. Antiretroviral agents not mentioned above can be administered regardless of food. There is insufficient evidence available to make recommendations about consuming juice or alcohol with antiretroviral drugs. Resolving drug-food interactions may contribute to maximized cART effectiveness and safety.

Effect of reducing the paediatric stavudine dose by half: a physiologically-based pharmacokinetic model

Owing to significant dose-related toxicity, the adult stavudine dose was reduced in 2007. The paediatric dose, however, has not been reduced. Although the intended paediatric dose is 1 mg/kg twice daily (b.i.d.), the current weight-band dosing approach results in a mean actual dose of 1.23±0.47 mg/kg. Both efficacy and mitochondrial toxicity depend on the concentration of the intracellular metabolite stavudine triphosphate (d4T-TP). We simulated the effect of reducing the paediatric dose to 0.5 mg/kg. A physiologically-based pharmacokinetic model consisting of 13 tissue compartments plus a full ADAM model was used to describe the elimination of stavudine. The volume of distribution at steady-state and apparent oral clearance were simulated and the resulting AUC profile was compared with literature data in adult and paediatric populations. A biochemical reaction model was utilised to simulate intracellular d4T-TP levels for both the standard and proposed reduced paediatric doses. Simulated and observed exposure after oral dosing showed adequate agreement. Mean steady-state d4T-TP for 1.23 mg/kg b.i.d. was 27.9 (90% CI 27.0-28.9) fmol/10(6) cells, 25% higher than that achieved by the 40 mg adult dose. The 0.5 mg/kg dose resulted in d4T-TP of 13.2 (12.7-13.7) fmol/10(6) cells, slightly higher than the adult dose of 20 mg b.i.d. [11.5 (11.2-11.9) fmol/10(6) cells], which has excellent antiviral efficacy and substantially less toxicity. Current paediatric dosing may result in even higher d4T-TP than the original 40 mg adult dose. Halving the paediatric dose would significantly reduce the risk of mitochondrial toxicity without compromising antiviral efficacy.

The Bioavailability of the Novel Nonnucleoside Reverse Transcriptase Inhibitor GW420867X Is Unaffected by Food in Healthy Male Volunteers

The effect of food on the bioavailability of GW420867X, a novel nonnucleoside reverse transcriptase inhibitor, was investigated in 15 young, healthy, male volunteers. A single oral dose of GW420867X 100 mg was administered in the fasted state, after a high-fat meal, and after a meal of normal fat composition. Tolerability and pharmacokinetic sampling were assessed at baseline and up to 600 hours. The median concentration-time plots for each treatment group were essentially superimposable. Neither the rate nor the extent of absorption of GW420867X was significantly affected by food. The median time to peak plasma concentration was 3 to 4 hours, irrespective of treatment. Pairwise comparisons using the fasted treatment as the comparator showed no impact of food on GW420867X pharmacokinetics. GW420867X was well tolerated. There were no serious or treatment-limiting adverse events; all episodes reported were rated as mild to moderate. The bioavailability of GW420867X was unaffected by food. GW420867X may be administered independently of food and fat intake.

Absence of Food Effect on the Pharmacokinetics of Telbivudine Following Oral Administration in Healthy Subjects

The influence of food on the pharmacokinetics of telbivudine, a candidate antiviral agent against hepatitis B virus (HBV), was investigated in healthy adult subjects following a 600-mg oral dose administered with and without a high-fat/high-calorie meal. Telbivudine was well tolerated under fasting and fed conditions. Oral absorption of telbivudine as measured by maximum plasma concentration (Cmax), time to reach Cmax (Tmax), and area under the plasma concentration-time curve (AUC(0-t) and AUC(0-infinity)) was not altered by food intake immediately before oral dosing. Values of Cmax, Tmax, and AUC were comparable when telbivudine was administered under fed and fasting conditions. Results from this study indicated that the absorption of telbivudine was not affected by a high-fat/high-calorie meal; telbivudine can therefore be administered orally with no regard to the timing of meals.

Pharmacokinetics of lamivudine & stavudine in generic fixed-dose combinations in HIV-1 infected adults in India

BACKGROUND & OBJECTIVES

Antiretroviral drug concentrations are important determinants of clinical response to a drug accounting for both toxicity and efficacy. Several factors such as age, ethnicity, body weight and patients' immune status may influence antiretroviral drug concentrations. The aim of the study was to determine the influence of immunological status, sex and body mass index on the steady state pharmacokinetics of lamivudine (3TC) and stavudine (d4T) in HIV-infected adults, who were undergoing treatment with generic fixed dose combinations (FDC) of these drugs in India.

METHODS

Twenty seven HIV-1 infected patients receiving antiretroviral treatment (ART) for at least two weeks at the Government ART clinic at Tambaram, Chennai, took part in the study. Serial blood samples were collected predosing and at different time points after drug administration. Plasma 3TC and d4T levels were estimated by HPLC.

RESULTS

The patients' immune status, sex or body mass index had no impact on the pharmacokinetics of 3TC. In the case of d4T, peak concentration was significantly lower in patients with CD4 cell counts < 200 cells/microl than those with > or = 200 cells/ microl (P < 0.05), but were within the therapeutic range. The mean CD4 cell counts increased from 101 cells/microl at initiation of ART to 366 cells/microl at 12 months of treatment.

INTERPRETATION & CONCLUSIONS

Blood levels of 3TC and d4T drugs that are part of generic FDCs commonly used by HIV-infected individuals in India were within the therapeutic range and not influenced by nutritional or immune status. There was a significant improvement in CD4 cell counts over 12 months of treatment. Indian generic FDCs manufactured and used widely in the developing world provide effective concentrations of antiretroviral drugs.

High Doses of Stavudine Induce Fat Wasting and Mild Liver Damage without Impairing Mitochondrial Respiration in Mice

Objective

Stavudine (d4T), a nucleoside reverse-transcriptase inhibitor (NRTI), can induce lipoatrophy, fatty liver, hyperlactataemia and abnormal liver tests. NRTI toxicity is usually ascribed to mitochondrial DNA (mtDNA) depletion and impaired mitochondrial respiration. However, NRTIs could have effects unrelated to mtDNA. Recently, we reported that 100 mg/kg/day of d4T stimulated fatty acid oxidation (FAO) in mouse liver, and reduced body fatness without depleting white adipose tissue (WAT) mtDNA. We hypothesized that higher d4T doses could further reduce adiposity, while inhibiting hepatic FAO.

Methods

Mice were treated for 2 weeks with d4T (500 mg/kg/day), L-carnitine (200 mg/kg/day) or both drugs concomitantly. Body fatness was assessed by dual energy X-ray absorptiometry, and investigations were performed in plasma, liver, muscle and WAT.

Results

D4T reduced the gain of body adiposity, WAT leptin, whole body FAO and plasma ketone bodies, and increased liver triglycerides and plasma aminotransferases with mild ultrastructural abnormalities in hepatocytes. Plasma lactate and respiratory chain activities in tissues were unchanged. Stearoyl-CoA desaturase (SCD-1), an enzyme negatively regulated by leptin, was overexpressed in liver. High doses of β-aminoisobutyric acid (BAIBA), a d4T catabolite, increased plasma ketone bodies. Although L-carnitine did not correct body adiposity, it prevented d4T-induced impairment of FAO and liver abnormalities.

Conclusions

D4T overdosage triggers fat wasting, leptin insufficiency and mild liver damage, without causing respiratory chain dysfunction. Overexpression of SCD-1 reduces fatty acid oxidation and overcomes the stimulating effect of BAIBA on hepatic FAO. L-carnitine does not correct leptin insufficiency but prevents d4T-induced impairment of FAO and liver damage.

Bioequivalence evaluation of two marketed brands of stavudine 40mg capsules in healthy human South African volunteers

Stavudine (d4T), a thymidine nucleoside analogue has been effectively used for treatment of patients infected with HIV. A randomized, two-way, crossover study was conducted in 24 fasting, healthy, Caucasian male volunteers to compare plasma pharmacokinetic (PK) profile and single-dose tolerability of a new d4T formulation (Stavir, Cipla Ltd, India; 40 mg capsule, test, T) with that of reference (R) formulation (Zerit), Bristol-Myers Squib, NJ, USA; capsule, 40 mg). Each volunteer received T and R formulation separated by at least 10 days of drug free wash-out period. Plasma concentrations of d4T, determined upto 24h post-dose by a validated LC-MS/MS assay were utilized to assess PK parameters such as maximum observed plasma concentration (Cmax), time to Cmax (tmax), and area under plasma concentration curve (AUC(infinity)). The primary plasma PK parameters, Cmax, and AUC(infinity), of anti-retroviral were comparable for either of the formulations. tmax was achieved within an hour suggesting rapid absorption of d4T from both formulations. Geometric mean ratios (GMR) (percentage reference) of AUC(infinity) and Cmax, and their 90% confidence intervals (CI) were 106.32 [102.52-110.26] and 102.32 [90.25-116.00], respectively. As the 90% CI of GMR were entirely within 80-125% for log-transformed parameters, two formulations were considered bioequivalent, in the extent and rate of absorption. Both formulations exhibited similar tolerability under fasting conditions.

Pharmacokinetics of GW433908, a prodrug of amprenavir, in healthy male volunteers

These two Phase I, open-label, single-dose, randomized, crossoverstudies in 40 healthymale subjects investigated the pharmacokinetic and safety profiles of various formulations of the amprenavir prodrug GW433908 in the presence and absence of food compared with amprenavir capsules. GW433908 is a phosphate ester prodrug of the antiretroviral protease inhibitor amprenavir, with improved solubility over the parent molecule and a potential for reduced pill burden on current dosing regimens. The calcium salt of the prodrug, GW433908G, was selected for further investigation, as it appeared to offer the greatest potential for the development of new drug formulations. In the fasting state, (1) GW433908G tablet and suspension were bioequivalent in terms of both AUC and Cmax, and (2) GW433908G tablet and suspension were bioequivalent to amprenavir capsules for AUC; however, Cmax was lower with GW433908G. After a high-fat meal compared with fasting, (1) the bioavailability of GW433908G suspension was decreased by 20% and Cmax by 41%, and (2) for GW433908G tablets, there was no influence on AUC(12% lower Cmax). After a low-fat meal compared with fasting, (1) there was bioequivalence for GW433908G tablets, but (2) bioavailability was decreased by 23% for amprenavir capsules (Cmax was also lower, by 46%). Overall, for GW433908G and amprenavir capsules, food had a negligible influence on plasma concentration at 12 hours postdose (C12). Whether administered as tablets or suspension, GW433908G pharmacokinetics was only slightly affected by food. GW433908G tablets were well tolerated and delivered plasma amprenavir concentrations equivalent to the recommended therapeutic amprenavir dose but with fewer tablets. The possibility of a lower pill burden offered by GW433908 may be of clinical benefit in the treatment of HIV infection.

Effect of food on the pharmacokinetics of (-) and (+) dOTC when administered as an oral racemate

The objective of this study was to evaluate the effect of food on the pharmacokinetics of racemic dOTC, a nucleoside analogue reverse transcriptase inhibitor, in adult male volunteers. Twelve healthy adult male subjects were enrolled in a randomized, open-label, single-dose crossover study. All were nonsmoking, within 15% of ideal body weight, and between 18 and 50 years of age. Subjects received single oral doses of 800mg racemic dOTC, in random order, either fed or fasted. The meal given to fed subjects was the standard Food and Drug Administration high-fat breakfast, and all subjects completed both study periods. Sixteen plasma samples for pharmacokinetic assessments were collected for 72 hours following dosing and assayed for (-) and (+) dOTC concentrations. Area under the plasma concentration-time curve (AUC), maximum observed plasma concentration (Cmax), and time to maximum concentration (tm) were determined for each enantiomer by standard noncompartmental techniques. Statistical hypothesis testing was by Wilcoxon signed rank, and the two one-sided tests procedure was used to determine bioequivalence between thefed and fasted study periods. The only effect of coadministration of racemic dOTC with food was a delay in time to peak concentration (t(max) of between 0.6 and 0.7 hours for both (-) and (+) dOTC stereoisomers (p < or =0.02). Neither AUC (p > or = 0.10) nor Cmax (p > or = 0.35) differed significantly between the fed and fasted study periods for either (-) or (+) dOTC. Both AUC and Cmax were equivalent between the fed and fasted study periods. It was concluded that there is no clinically significant effect of a high-fat meal on the pharmacokinetics of either (-) or (+) dOTC when administered orally as a racemic mixture.

Stavudine: an update of its use in the treatment of HIV infection

Stavudine is a thymidine nucleoside analogue which is phosphorylated intracellularly to an active metabolite, stavudine 5'-triphosphate. This metabolite inhibits HIV replication, either by competing with thymidine 5'-triphosphate for incorporation into viral DNA by reverse transcriptase or by causing premature termination of the viral chain after incorporation. Resistance to stavudine, either alone or as part of resistance to multiple nucleoside reverse transcriptase inhibitors, has been reported; however, high-level resistance is uncommon even after long periods of treatment. Initial treatment with stavudine-containing triple therapies reduced HIV RNA levels to below the limit of detection (LOD; 500 copies/ml) in 68 to 100% of antiretroviral-naive patients after at least 20 weeks of treatment. Effects on clinical outcomes have not yet been established, although earlier trials showed significant improvements with stavudine (alone or with 1 other drug) in patients who had previously received zidovudine. Results from 2 randomised nonblind clinical trials indicated that the efficacy of stavudine-containing triple therapy was similar to that of zidovudine-containing triple therapy (when used in combination with the same drugs), although there were no statistical comparisons. Improvements in surrogate end-points have also been seen in trials in antiretroviral-experienced patients receiving stavudine and 2 or 3 other antiretroviral agents. Stavudine-containing combination therapies have also been effective in reducing viral load and increasing CD4+ lymphocyte count in children, although data are limited. Like other nucleoside analogues, stavudine treatment can cause mitochondrial toxicity. The major adverse effect from this observed with stavudine therapy is peripheral neuropathy, which is both dosage- and treatment duration-dependent. Most cases respond to short term cessation of treatment and reintroduction of stavudine at half the previous dosage.

CONCLUSION

Stavudine-containing triple therapies are effective in the treatment of antiretroviral-naive adults with HIV infection as assessed by surrogate end-points; earlier trials involving 1 or 2-drug therapy showed that stavudine can significantly improve clinical end-points. Stavudine has also been beneficial as part of combination regimens in antiretroviral-experienced patients and children with HIV infection, although data are limited and more studies are needed. High-level resistance to stavudine is uncommon. The major adverse event associated with treatment is peripheral neuropathy, which may limit its use in some patients. Currently, stavudine has a valuable role as part of initial triple therapy in antiretroviral-naive adults with HIV/AIDS.

Effects of food on clinical pharmacokinetics

Food-drug interactions can be associated with alterations in the pharmacokinetic and pharmacodynamic profile of various drugs that may have clinical implications. The various phases in which food may interact with a coadministered drug are: (i) before and during gastrointestinal absorption; (ii) during distribution; (iii) during metabolism; and (iv) during elimination. Absorption and metabolism are the phases where food has most effect, and this review will focus on those areas. It will also review the variable and complex effects of antacids and metal ions on drug absorption. Mechanisms related to food effects on drug absorption have been described under 5 categories: those causing decreased, delayed, increased or accelerated absorption, and those in which food has no significant effect. Among the major variables that interface between differential effects of food and postprandial bioavailability are: (i) the physicochemical characteristics and enantiomorphic composition of the drug; (ii) timing of meals in relation to time of drug administration; (iii) size and composition of meals (especially fat, protein and fibre); and (iv) dose size. However, the influence of food is largely a matter of the design of the pharmaceutical formulation. In addition, the mechanism of 'food effect' may involve physiological and sensory responses to food, such as changes in gastrointestinal milieu and gastric emptying rate, reflex action, and may also involve the site and route (either portal or lymphatic) of drug absorption. Mixing drugs with fruit juice, such as grapefruit and orange juice, and acidic beverages, such as commercial soft drinks, may affect absorption because of decreases in gastric pH, which could offer a therapeutic advantage in certain clinical conditions, such as patients with HIV disease and cancer. The increased bioavailability caused by the concomitant intake of grapefruit juice results from the inhibition of intestinal cytochrome P450(CYP)3A4, but not hepatic CYP3A4 or colon CYP3A5, which probably involves the bioflavonoid naringenin and furanocoumarins. Although there is a vast amount of literature, there is still no rational scientific basis to predict the effect of food for a particular chemical entity or a chemical class of therapeutic agents. A mechanistic understanding of the effects of food may serve as a key to the pharmacokinetic optimisation of patient therapy, both in outpatients and hospitalised patients of various age groups.