In Vitro Dissolution of Generic Immediate-Release Solid Oral Dosage Forms Containing BCS Class I Drugs: Comparative Assessment of Metronidazole,Zidovudine, and Amoxicillin Versus Relevant Comparator Pharmaceutical Products in South Africa and India

Biowaivers are recommended for immediate-release solid oral dosage forms using dissolution testing as a surrogate for in vivo bioequivalence studies. Several guidance are currently available (the World Health Organization (WHO), the US FDA, and the EMEA) where the conditions are described. In this study, definitions, criteria, and methodologies according to the WHO have been applied. The dissolution performances of immediate-release metronidazole, zidovudine, and amoxicillin products purchased in South African and Indian markets were compared to the relevant comparator pharmaceutical product (CPP)/reference product. The dissolution performances were studied using US Pharmacopeia (USP) apparatus 2 (paddle) set at 75 rpm in each of three dissolution media (pH1.2, 4.5, and 6.8). Concentrations of metronidazole, zidovudine, and amoxicillin in each dissolution media were determined by HPLC. Of the 11 metronidazole products tested, only 8 could be considered as very rapidly dissolving products as defined by the WHO, whereas 2 of those products could be considered as rapidly dissolving products but did not comply with the f₂ acceptance criteria in pH 6.8. All 11 zidovudine products were very rapidly dissolving, whereas in the case of the 14 amoxicillin products tested, none of those products met any of the WHO criteria. This study indicates that not all generic products containing the same biopharmaceutics classification system (BCS) I drug and in similar strength and dosage form are necessarily in vitro equivalent. Hence, there is a need for ongoing market surveillance to determine whether marketed generic products containing BCS I drugs meet the release requirements to confirm their in vitro bioequivalence to the respective reference product.KEY WORDS: BCS, dissolution testing, generic drug, immediate-release solid oral dosage forms, WHO criteria     

Investigating the Dissolution Profiles of Amoxicillin,Metronidazole, and Zidovudine Formulations used in Trinidad and Tobago,West Indies

Trinidad and Tobago is a twin-island Republic in the Caribbean and like many developing countries, it has included generic drugs on the national drug formulary to decrease the financial burden of pharmaceutical medications. However, to ensure that medications received by patients are beneficial, generic drugs need to be interchangeable with the innovator which has demonstrated safety, efficacy, and quality. The objective of the study was to compare the dissolution profiles and weight variations for different formulations of amoxicillin, metronidazole, and zidovudine that are on the national drug formulary and marketed in Trinidad and Tobago. All the products investigated are categorized as class 1 drugs according to the Biopharmaceutics Classification System (BCS) and the dissolution profiles were assessed according to the World Health Organization (WHO) criteria for interchangeability between products. The similarity factor, f₂, was used to determine sameness between the products. No generic formulation was found to be similar to Amoxil® 500-mg capsules. The two generic products for metronidazole 200-mg tablets demonstrated more than 85% drug release within 15 min in all three of the buffers; however, their 400-mg counterparts did not fulfill this requirement. The zidovudine 300-mg tablet complied with the requirements in buffer pH 4.5 and simulated gastric fluid (SGF) but not for simulated intestinal fluid (SIF). Some Class 1 pharmaceutical formulations may possess the same active ingredient and amount of drug but may show significant differences to in vitro equivalence requirements. Nevertheless, the dissolution process is suitable to detect these variations.KEY WORDS: biopharmaceutics classification system, dissolution, generic drugs, interchangeability, in vitro equivalence     

Biopharmaceutics Classification System-Based Biowaivers for Generic Oncology Drug Products: Case Studies

Establishing bioequivalence (BE) of drugs indicated to treat cancer poses special challenges. For ethical reasons, often, the studies need to be conducted in cancer patients rather than in healthy volunteers, especially when the drug is cytotoxic. The Biopharmaceutics Classification System (BCS) introduced by Amidon (1) and adopted by the FDA, presents opportunities to avoid conducting the bioequivalence studies in humans. This paper analyzes the application of the BCS approach by the generic pharmaceutical industry and the FDA to oncology drug products. To date, the FDA has granted BCS-based biowaivers for several drug products involving at least four different drug substances, used to treat cancer. Compared to in vivo BE studies, development of data to justify BCS waivers is considered somewhat easier, faster, and more cost effective. However, the FDA experience shows that the approval times for applications containing in vitro studies to support the BCS-based biowaivers are often as long as the applications containing in vivo BE studies, primarily because of inadequate information in the submissions. This paper deliberates some common causes for the delays in the approval of applications requesting BCS-based biowaivers for oncology drug products. Scientific considerations of conducting a non-BCS-based in vivo BE study for generic oncology drug products are also discussed. It is hoped that the information provided in our study would help the applicants to improve the quality of ANDA submissions in the future.KEY WORDS: Biopharmaceutics Classification System, bioequivalence, biowaiver, cancer, oncology     

Particle Size Distribution Equivalency as Novel Predictors for Bioequivalence

The use of particle size distribution (PSD) similarity metrics and the development and incorporation of drug release predictions based on PSD properties into PBPK models for various drug administration routes may provide a holistic approach for evaluating the effect of PSD differences on in vitro drug release and bioavailability of disperse systems. The objectives of this study were to provide a rational approach for evaluating the utility of in vitro PSD comparators for predicting bioequivalence for subcutaneously administered test and reference drug emulsions. Two types of in vitro comparators for test and reference emulsion products were evaluated: PSD characterization comparators (overlap metrics, median, and span ratios) and release profile comparators (f₂ and various fractional time ratios). A subcutaneous-input PBPK disposition model was developed to simulate blood concentration-time profiles of reference and test emulsion products and pharmacokinetic responses (e.g., AUC, C_max, and T_max) were used to determine bioequivalence. A pool of 10,440 pairs of test and reference products was simulated using Monte Carlo experiments. The PSD and release profile comparators were correlated to pass/fail bioequivalence metrics using logistical regression. Based on the use of single in vitro comparators, the f₂ method was the best predictor of bioequivalence prediction. The use of combinations of f₂ and PSD overlap comparators (e.g., OVL or PROB) improved bioequivalence prediction to about 90%. Simulation procedures used in this study demonstrated a process for developing reliable in vitro BE predictors.     

Determining the Polymer Threshold Amount for Achieving Robust Drug Release from HPMC and HPC Matrix Tablets Containing a High-Dose BCS Class I Model Drug: In Vitro and In Vivo Studies

It is challenging to achieve mechanically robust drug-release profiles from hydrophilic matrices containing a high dose of a drug with good solubility. However, a mechanically robust drug release over prolonged period of time can be achieved, especially if the viscosity and amount of the polymer is sufficiently high, above the “threshold values.” The goal of this research was to determine the hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) polymer threshold amount that would enable robust drug release from matrix tablets containing a high dose of levetiracetam as a class I model drug according to the Biopharmaceutical Classification System (BCS). For this purpose, formulations containing HPC or HPMC of similar viscosity range, but in different amounts, were prepared. Based on the dissolution results, two final formulations were selected for additional in vitro and in vivo evaluation to confirm the robustness and to show bioequivalence. Tablets were exposed to various stress conditions in vitro with the use of different mechanically stress-inducing dissolution methods. The in vitro results were compared with in vivo results obtained from fasted and fed bioequivalence studies. Under both conditions, the formulations were bioequivalent and food had a negligible influence on the pharmacokinetic parameters C_max and area under the curve (AUC). It was concluded that the drug release from both selected formulations is mechanically robust and that HPC and HPMC polymers with intrinsic viscosities above 9 dL/g and in quantities above 30% enable good mechanical resistance, which ensures bioequivalence. In addition, HPC matrices were found to be more mechanically robust compared to HPMC.KEY WORDS: HPC, HPMC, matrix tablets, mechanically robust dissolution, threshold amount     

Permeation of Four Oral Drugs Through Human Intestinal Mucosa

The pharmaceutical industry is in need of rapid and accurate methods to screen new drug leads for intestinal permeability potential in the early stages of drug discovery. Excised human jejunal mucosa was used to investigate the permeability of the small intestine to four oral drugs, using a flow-through diffusion system. The four drugs were selected as representative model compounds of drug classes 1 and 3 according to the biopharmaceutics classification system (BCS). The drugs selected were zidovudine, propranolol HCl, didanosine, and enalapril maleate. Permeability values from our in vitro diffusion model were compared with the BCS permeability classification and in vivo and in vitro gastrointestinal drug permeability. The flux rates of the four drugs were influenced by the length of the experiment. Both class 1 drugs showed a significantly higher mean flux rate between 2 and 6 h across the jejunal mucosa compared to the class 3 drugs. The results are therefore in line with the drugs’ BCS classification. The results of this study show that the permeability values of jejunal mucosa obtained with the flow-through diffusion system are good predictors of the selected BCS class 1 and 3 drugs’ permeation, and it concurred with other in vitro and in vivo studies.     

Application of Absorption Modeling to Predict Bioequivalence Outcome of Two Batches of Etoricoxib Tablets

As part of the overall product development and manufacturing strategy, pharmaceutical companies routinely change formulation and manufacturing site. Depending on the type and level of change and the BCS class of the molecule, dissolution data and/or bioequivalence (BE) may be needed to support the change for immediate release dosage forms. In this report, we demonstrate that for certain weakly basic low-solubility molecules which rapidly dissolve in the stomach, absorption modeling could be used to justify a BE study waiver even when there is failure to show dissolution similarity under some conditions. The development of an absorption model for etoricoxib is described here, which was then used to a priori predict the BE outcome of tablet batches manufactured at two sites. Dissolution studies in 0.01 N HCl media (pH 2.0) had demonstrated similarity of etoricoxib tablets manufactured at two different sites. However, dissolution testing at pH 4.5 and pH 6.8 media failed to show comparability of the tablets manufactured at the two sites. Single simulations and virtual trials conducted using the 0.01 N HCl dissolution showed similarity in AUC and C_max for all tablet strengths for batches manufactured at the two manufacturing sites. These predicted results were verified in a definitive bioequivalence study, which showed that both tablet batches were bioequivalent. Since the development of traditional in vitro–in vivo correlations (IVIVC) for immediate release (IR) products is challenging, in cases such as etoricoxib, absorption modeling could be used as an alternative to support waiver of a BE study.KEY WORDS: bioequivalence, dissolution, modeling, pharmacokinetics, SUPAC     

An Investigation into the Influence of Experimental Conditions on In Vitro Drug Release from Immediate-Release Tablets of Levothyroxine Sodium and Its Relation to Oral Bioavailability

The aim of this study was to investigate the influence of experimental conditions on levothyroxine sodium release from two immediate-release tablet formulations which narrowly passed the standard requirements for bioequivalence studies. The in vivo study was conducted as randomised, single-dose, two-way cross-over pharmacokinetic study in 24 healthy subjects. The in vitro study was performed using various dissolution media, and obtained dissolution profiles were compared using the similarity factor value. Drug solubility in different media was also determined. The in vivo results showed narrowly passing bioequivalence. Considering that levothyroxine sodium is classified as Class III drug according to the Biopharmaceutics Classification System, drug bioavailability will be less sensitive to the variation in its dissolution characteristics and it can be assumed that the differences observed in vitro in some of investigated media probably do not have significant influence on the absorption process, as long as rapid and complete dissolution exists. The study results indicate that the current regulatory criteria for the value of similarity factor in comparative dissolution testing, as well as request for very rapid dissolution (more than 85% of drug dissolved in 15 min), are very restricted for immediate-release dosage forms containing highly soluble drug substance and need further investigation. The obtained results also add to the existing debate on the appropriateness of the current bioequivalence standards for levothyroxine sodium products.KEY WORDS: bioequivalence, dissolution, immediate release, levothyroxine sodium, solubility     

Using pH Gradient Dissolution with <Emphasis Type="Italic">In-Situ</Emphasis> Flux Measurement to Evaluate Bioavailability and DDI for Formulated Poorly Soluble Drug Products

This study described a pH-gradient dissolution method combined with flux measurements as an in vitro tool for assessing the risk of bioavailability reduction due to drug-drug interactions (DDI) caused by acid reducing agents (ARAs). The device incorporates absorption chambers into USP II dissolution vessels, with fiber optic UV-probes monitoring concentration in situ. Dosage forms of Genentech BCS class II drugs, GDC-0810, GDC-0941, and compound A, were tested by starting the dissolution in either pH 1.6 or pH 4.0 media then converting to FaSSIF after 30 min. GDC-0810 showed no significant difference in flux between the two conversion experiments. A supersaturation phase was observed for GDC-0941 in the pH 1.6 experiments after media conversion to FaSSIF; however, it did not appear to occur in the pH 4.0 experiment due to low drug solubility at pH 4.0, resulting in a 95% decrease in flux compared to pH 1.6 experiment. The extent of flux reduction and the total accumulated API mass in the absorption chamber agreed well with the 89% reduction in mean Cmax and the 82% reduction in mean AUC from dog PK study between animals treated with pentagastrin and famotidine. Testing of the compound A optimized formulation tablets showed a 25% reduction in flux and in vitro absorbed amount by changing pH 1.6 to 4.0, correlating well with the AUC decrease in clinical studies. Good correlation between in vitro data and in vivo PK data demonstrated the applicability of the method for formulators to develop drug products mitigating DDI from ARAs.     

Primary antibiotic resistance and associated mechanisms in Helicobacter pylori isolates from Senegalese patients

Background

Antibiotic combination therapy for Helicobacter pylori eradication must be adapted to local resistance patterns, but the epidemiology of H. pylori resistance to antibiotics is poorly documented in Africa. The aim was to determine the antibiotic resistance rates, as well as the associated molecular mechanisms, of strains isolated in Dakar, Senegal.

Methods

One hundred and eight H. pylori strains were isolated between 2007 and 2009 from 108 patients presenting with upper abdominal pain to the Gastroenterology Department of Le Dantec Hospital. Antimicrobial susceptibility testing was performed for amoxicillin, clarithromycin, metronidazole, levofloxacin and tetracyclin using the E-test method. Mutations in the 23S rRNA gene of clarithromycin-resistant strains and in gyrA and gyrB of levofloxacin-resistant strains were investigated.

Results

Isolates were characterized by no resistance to amoxicillin (0%), tetracycline (0%), and very low rate of resistance to clarithromycin (1%), but a high rate of resistance to metronidazole (85%). The clarithromycin-resistant strain displayed the A2143G mutation. A worrying rate of levofloxacin resistance was detected (15%). N87I and D91N were the most common mutations in the quinolone-resistance-determining region of gyrA.

Conclusions

The first-line empirical regimen for H. pylori eradication in Senegal should include clarithromycin. Increasing rates of fluoroquinolone resistance detected should discourage the use of levofloxacin-containing regimens without prior antimicrobial susceptibility testing.     

Tritrichomonas foetus: Stable anaerobic resistance to metronidazole in vitro

Stable anaerobic resistance of Tritrichomonas foetus to metronidazole was induced in vitro by cultivation of trichomonads in the Diamond's TYM medium with metronidazole in concentrations sublethal to the parasites. Nine metronidazole-resistant strains were derived from four drug-susceptible clones of the T. foetus strain KV-1. Subculturing the parasites at both increasing and constant pressure of the drug resulted in development of resistance if the medium contained at least 3 μg ml^?1 of metronidazole and the organisms were exposed to the drug for 3 to 8 months. The development of resistance was gradual and in all clones investigated proceeded through similar sequence of stages: (1) Survival without growth and subsequent reproduction at low metronidazole concentrations (1 to 5 μg ml^?1. (2) Survival and reproduction at moderate concentrations of the drug (10 to 15 μg ml^?1. (3) Resistance to 100 μg ml^?1 metronidazole, unstable in absence of selective pressure of the drug. (4) Resistance to high concentrations of metronidazole, stable when the organisms were maintained under nonselective conditions. The trichomonads with fully developed resistance were able to grow in anaerobic culture at 100 μg ml^?1 metronidazole and could be maintained indefinitely under these conditions. The minimal lethal concentrations for metronidazole obtained with these strains in an anaerobic in vitro assay were, at 48 h, 500 to 1000 μg ml^?1. This is 100 to 400 times higher than those obtained with the parent clones. The fully developed resistance was stable in organisms maintained in the absence of the drug over 2 years. The substrains with unstable resistance regained the susceptibility to high concentrations of metronidazole after 80 to 100 transfers in drug-free media. These strains, however, retained their resistance to moderate doses of metronidazole and full resistance could be restored by subculture in the presence of 10 μ ml^?1 metronidazole.     

Lidocaine Transdermal Patch: Pharmacokinetic Modeling and <Emphasis Type="Italic">In Vitro</Emphasis>–<Emphasis Type="Italic">In Vivo</Emphasis> Correlation (IVIVC)

The present study aims to develop the correlation between in vitro and in vivo skin permeation of lidocaine in its transdermal patch. In order to minimize the run-to-run variability during in vitro skin permeation studies, release normalized cumulative percent (%Ct _n) was calculated. A suitable polynomial mathematical model was used to establish a correlation between time and %Ct _n. Percent in vivo absorbed was calculated by using numerical deconvolution (NDC) and non-compartmental analysis (NCA) methods. Pharmacokinetic (PK) parameters such as AUC _last and C _max were predicted with the established in vitro–in vivo correlation (IVIVC) models. The minimum prediction errors in NDC method for C _max were found to be ?30.9 and ?25.4% for studies I (in vivo study in human volunteers with one batch of Lidoderm patch; internal validation) and II (in vivo study in human volunteers with another batch of Lidoderm patch; external validation), respectively, whereas minimum prediction errors in NCA method were relatively low (3.9 and 0.03% for studies I and II, respectively) compared to those in NDC method. The prediction errors for AUC _last were found to be less than 2% for both methods and studies. The established method in this study could be a potential approach for predicting the bioavailability and/or bioequivalence for transdermal drug delivery systems.     

Effects of the Preparation Process on the Properties of Amorphous Solid Dispersions

The use of amorphous solid dispersions to improve the bioavailability of active ingredients from the BCS II and IV classifications continues to gain interest in the pharmaceutical industry. Over the last decade, methods for generating amorphous solid dispersions have been well established in commercially available products and in the literature. However, the amorphous solid dispersions manufactured by different technologies differ in many aspects, primarily chemical stability, physical stability, and performance, both in vitro and in vivo. This review analyzes the impact of manufacturing methods on those properties of amorphous solid dispersions. For example, the chemical stability of drugs and polymers can be influenced by differences in the level of thermal exposure during fusion-based and solvent-based processes. The physical stability of amorphous content varies according to the thermal history, particle morphology, and nucleation process of amorphous solid dispersions produced by different methods. The in vitro and in vivo performance of amorphous formulations are also affected by differences in particle morphology and in the molecular interactions caused by the manufacturing method. Additionally, we describe the mechanism of manufacturing methods and the thermodynamic theories that relate to amorphous formulations.     

Simulation of In Vitro Dissolution Behavior Using DDDPlus?

Dissolution testing is a performance test for many dosage forms including tablets and capsules. The objective of this study was to evaluate if computer simulations can predict the in vitro dissolution of two model drugs for which different dissolution data were available. Published montelukast sodium and glyburide dissolution data was used for the simulations. Different pharmacopeial and biorelevant buffers, volumes, and rotations speeds were evaluated. Additionally, a pH change protocol was evaluated using these buffers. DDDPlus™ 3, Beta version (Simulation Plus, Inc.), was used to simulate the in vitro dissolution data. The simulated data were compared with the in vitro data. A regression coefficient between predicted and observed data was used to assess the simulations. The statistical analysis of Montelukast sodium showed that there was a significant correlation between the in vitro release data and the predicted data for all cases except for one buffer. For glyburide, there was also a significant correlation between the experimental data and the predicted data using single pH conditions. Using the dynamic pH protocol, a correlation was significant for one biorelevant media. The simulations showed that both in vitro drug releases were sensitive to solubility effects which confirmed their BCS class II category. Computer simulations of the in vitro release using DDDPlus™ have the potential to estimate the in vivo dissolution at an early stage in the drug development process. This might be used to choose the most appropriate dissolution condition to establish IVIVC and to develop biorelevant in vitro performance tests to capture critical product attributes for quality control procedures in quality by design environments.KEY WORDS: biorelevant media, DDDPlus, dissolution testing, QbD, QC     

Dietary Iodine Affected the GSH-Px to Regulate the Thyroid Hormones in Thyroid Gland of Rex Rabbits

Iodine (I) is an essential trace element that can influence animal health and productivity. In this study, we investigated the effects of dietary iodine on the antioxidant indices of organ (liver and thyroid gland) and messenger RNA (mRNA) expression of glutathione peroxidase (GSH-Px) in Rex rabbits. A total of 120 4-month-old Rex rabbits (2235.4 ± 13.04 g BW) were divided into four equal groups, and their diets were supplemented with iodine (0, 0.2, 2, or 4 mg/kg dry matter (DM)). The iodine concentration in basal diet (control group) was 0.36 mg/kg DM. In most of measured parameters, supplemental iodine exerted no significant effect. Growth and slaughter performance and organ weight were not influenced significantly by iodine supplementation. Serum T₃ was significantly lower in 2-mg I group than in 0.2 and 4-mg I groups (P < 0.05). Superoxide dismutase (SOD), GSH-Px, methane dicarboxylic aldehyde (MDA), and thyroperoxidase (TPO) in the serum and liver were not influenced (P > 0.05). Conversely, serum catalase (CAT) was significantly reduced (P < 0.05). In the thyroid, GSH-Px was higher in the 2-mg I group than in the 0.2- and 4-mg I groups (P < 0.05). RT-PCR results showed that the mRNA expression level of GSH-Px in the liver was not significantly influenced (P > 0.05). In the thyroid gland, the mRNA expression level of GSH-Px was higher in the 2-mg I group than in the 4-mg I group (P < 0.05), which agreed with the activity of GSH-Px. In conclusion, iodine supplementation exerted no effect on the performance and antioxidant capacity of the body, but dietary iodine influenced serum T₃ or GSH-Px in the thyroid gland. Thus, on the basis of serum T₃ and GSH-Px levels in the thyroid gland, we hypothesized that GSH-Px secretion was increased by adding dietary iodine in the thyroid, which may inhibit the H₂O₂ generation and further influence the thyroid hormone synthesis.     

A Randomized Clinical Trial to Determine the Efficacy of Regimens Containing Clarithromycin, Metronidazole, and Amoxicillin Among Histologic Subgroups for Helicobacter pylori Eradication in a Developing Country

Background: Most treatments deemed effective for Helicobacter pylori eradication in developed countries are less effective in developing countries. Regimens containing clarithromycin, metronidazole, and amoxicillin seem efficacious despite antibiotic resistance, and may be a viable option in developing countries. Materials and Methods: We evaluated the efficacy of a 14‐day regimen with 500 mg clarithromycin b.i.d., 500 mg metronidazole t.i.d., and 500 mg amoxicillin t.i.d. (with and without a proton pump inhibitor), and a 10‐day regimen containing 500 mg clarithromycin b.i.d., 1 g amoxicillin b.i.d., and 20 mg omeprazole b.i.d. in Pasto, Colombia, using a randomized, single‐blind design stratified by presence of atrophic gastritis. Results: H. pylori was eradicated in 86.8% and 85.3% of the participants randomized to a clarithromycin‐metronidazole‐amoxicillin and clarithromycin‐amoxicillin‐omeprazole regimens, respectively (p = .79). Per‐protocol analyses indicated greater efficacy for the clarithromycin‐metronidazole‐amoxicillin regimen (97%) versus the clarithromycin‐amoxicillin‐omeprazole regimen (86%) (p = .04), particularly for participants with atrophic gastritis (clarithromycin‐metronidazole‐amoxicillin = 100%, clarithromycin‐amoxicillin‐omeprazole = 81%; p = .02). Adverse events were mild, but adverse event‐related non‐compliance was reported more often for regimens containing clarithromycin, metronidazole, and amoxicillin. Conclusions: Our results suggest that an eradication rate of > 85% can be achieved with 14‐day clarithromycin, metronidazole, and amoxicillin and 10‐day clarithromycin, amoxicillin, and omeprazole regimens in Pasto, Colombia. The regimens containing clarithromycin, metronidazole, and amoxicillin appear to be superior to the clarithromycin, amoxicillin, and omeprazole regimen for compliant participants and those with atrophic gastritis. Our findings provide treatment options for a population in a developing country with a high prevalence of H. pylori infections and antibiotic resistance.     

Comparison of In Vitro Release Rates of Acyclovir from Cream Formulations Using Vertical Diffusion Cells

Acyclovir, indicated in the treatment of herpes labialis (“cold sores”), is formulated as semisolid topical dosage forms and marketed in numerous countries. Since the formulations of the various acyclovir products may differ from country to country, this study was undertaken to compare the in vitro release of acyclovir from various generic cream products available on the South African and Indian markets using the respective brand/innovator product as the reference product. The in vitro studies were carried out using vertical diffusion cells with a diffusional surface area of 1.767 cm² and various commercially available membranes. Normal saline was used as receptor fluid and the temperature maintained at 32 ± 0.5°C. The in vitro release comparisons were based on the recommendations described in the US Food and Drug Administration Draft Guidance for acyclovir ointment and the SUPAC-SS Guidance for non-sterile semisolid dosage forms. The release rates (slope) of the test (T) and the relevant reference product (R) were monitored and compared. The comparative release of acyclovir from the various generic formulations compared with the reference product was found to be within the limits of 75–133.33% with a 90% confidence interval. These experiments indicate that the generic acyclovir cream formulations exhibited release rates that were comparable to the innovator product and could be considered to be bioequivalent.KEY WORDS: acyclovir cream, FDA Guidance, in vitro release, membranes, vertical diffusion cells     

Surveillance and trends of antimicrobial resistance among clinical isolates of anaerobes in Kuwait hospitals from 2002 to 2007

The susceptibility trends for all anaerobes processed by the Anaerobe Reference Laboratory against various antibiotics were determined by using data for 2557 isolates referred by all government hospitals in Kuwait from 2002 to 2007. MIC were determined for the following anti-anaerobic antibiotics: amoxicillin–clavulanic acid, clindamycin, imipenem, meropenem, metronidazole, penicillin, piperacillin, piperacillin–tazobactam and vancomycin (for Gram-positive anaerobes only), using E-test method. The commonest isolates were Bacteroides fragilis (36.8%), followed by Peptostreptococcus spp. (21.9%), Bacteroides ovatus (15.5%) and Prevotella bivia (12.1%). In addition, Prevotella oralis and other Bacteroides spp. represented 8.5% and 8.1% of total number of isolates, respectively. Resistance rate varied among the antimicrobial agents and the species tested. The β-lactams, with the exception of penicillin, were the most active drugs. Piperacillin–tazobactam was the only antimicrobial agent to which all the isolates were uniformly susceptible. Imipenem and metronidazole were highly active with resistance rate of only <5% recorded against most isolates. However, 42.8, 55.8 and 9.3% of Clostridium difficile isolates were resistant to imipenem, clindamycin and meropenem, respectively. It is noteworthy that from 2002 to 2007, there was a gradual increase in resistance rates to clindamycin, amoxicillin–clavulanic acid and piperacillin among B. fragilis. Periodic surveillance of antibiotic resistance among the anaerobic bacteria is recommended as a guide to empiric antibiotic use and formulation of guideline for appropriate choice of antimicrobial therapy in anaerobic infections.     

Effects of some drugs on human erythrocyte 6-phosphogluconate dehydrogenase: an in vitro study

Inhibitory effects of some drugs were investigated on human erythrocyte 6-phosphogluconate dehydrogenase obtained with a 6552-fold purification in a yield of 78% using 2′, 5′-ADP Separose 4B affinity gel. Which on SDS polyacrylamide gel electrophoresis showed a single band. Larnoxicam, metronidazole, imipenem, ornidazole, vancomycin, clindamycin, and amoxicillin exhibited inhibitory effects on the enzyme in vitro with IC₅₀ values of 0.17, 0.23, 0.43, 21.79, 46.39, 117.43 and 287.35 mM, and the Ki constants 0.40 ± 0.04, 0.57 ± 0.06, 0.77 ± 0.11, 42.40 ± 2.89, 65.60 ± 4.03, 130.22 ± 9.21, and 287.58 ± 10.56 mM, respectively. While vancomycin, clindamycin and amoxicillin showed competitive inhibition the other drugs displayed noncompetitive inhibition.     

Antineoplastic kinase inhibitors: A new class of potent anti-amoebic compounds

Entamoeba histolytica is a protozoan parasite which infects approximately 50 million people worldwide, resulting in an estimated 70,000 deaths every year. Since the 1960s E. histolytica infection has been successfully treated with metronidazole. However, drawbacks to metronidazole therapy exist, including adverse effects, a long treatment course, and the need for an additional drug to prevent cyst-mediated transmission. E. histolytica possesses a kinome with approximately 300–400 members, some of which have been previously studied as potential targets for the development of amoebicidal drug candidates. However, while these efforts have uncovered novel potent inhibitors of E. histolytica kinases, none have resulted in approved drugs. In this study we took the alternative approach of testing a set of twelve previously FDA-approved antineoplastic kinase inhibitors against E. histolytica trophozoites in vitro. This resulted in the identification of dasatinib, bosutinib, and ibrutinib as amoebicidal agents at low-micromolar concentrations. Next, we utilized a recently developed computational tool to identify twelve additional drugs with human protein target profiles similar to the three initial hits. Testing of these additional twelve drugs led to the identification of ponatinib, neratinib, and olmutinib were identified as highly potent, with EC₅₀ values in the sub-micromolar range. All of these six drugs were found to kill E. histolytica trophozoites as rapidly as metronidazole. Furthermore, ibrutinib was found to kill the transmissible cyst stage of the model organism E. invadens. Ibrutinib thus possesses both amoebicidal and cysticidal properties, in contrast to all drugs used in the current therapeutic strategy. These findings together reveal antineoplastic kinase inhibitors as a highly promising class of potent drugs against this widespread and devastating disease.