Fitting Pharmacodynamic Data to the Emax Model to Assess the Inherent Potency of Topical Corticosteroids.

The widespread use of topical corticosteroids (TCs) in dermatotherapy requires a consideration of their potency and benefit/risk ratios. Although there are a variety of topical corticosteroid products (TCPs) available on the market and their potencies are ranked using different classification systems, to our knowledge, no classification system to rank the inherent potencies of TC active pharmaceutical ingredients (APIs) currently exists. Most of the published classification systems for TCPs are based on randomized clinical comparative studies and/or vasoconstrictor assay (VCA) data. The objective was to apply the US FDA's VCA to classify the inherent potencies of several TCs using standardized doses to make appropriate comparisons of the relevant APIs in solutions of the same molar concentrations. Six TC APIs were assessed for their relative potencies using healthy human participants. The Emax model was used to fit skin blanching data following application of the respective TCs, and the parameters, Emax and ED50, were derived. Emax values were used as the metric to assess potency. Statistical analyses of the data revealed that the inherent potencies of fluticasone propionate, mometasone furoate, and hydrocortisone butyrate were similar. However, there was no significant difference between hydrocortisone butyrate and clobetasol propionate, while there was a significant difference between clobetasol propionate, fluticasone propionate, and mometasone furoate. Hence, the potency of hydrocortisone butyrate appears to overlap two potency classes. Furthermore, the potencies of betamethasone valerate and methylprednisolone aceponate were similar but lower than those of all of the other APIs. The application of the VCA to classify inherent potency provides a reliable method to establish a classification system for TCs. Inherent potency assessment of TCs provides information that will be useful when choosing an appropriate TC for the development of a TCP for a specific clinical indication.

Application of a dermatopharmacokinetic (DPK) method for bioequivalence assessment of topical metronidazole creams.

PURPOSE: The main aim of the current research was to develop and apply a dermatopharmacokinetic (DPK) approach for the bioequivalence assessment of metronidazole (MTZ) topical cream products, indicated in the treatment of rosacea. METHODS: A DPK methodology using tape stripping (TS) technique was developed by investigating the factors that may influence the TS results viz. tapes, dose durations, number of tapes to be used, pressure application, dose applied and gravimetric analysis of the tapes. An initial dose duration study was performed on 6 healthy participants to determine an appropriate application time duration using the Emax model. The SC thickness was normalised between participants using TEWL measurements. A pivotal study was conducted using both the arms of 10 healthy human participants to demonstrate the ability of the TS method for bioequivalence assessment by comparing the reference product to itself as a positive control and including products with higher and lower strengths of MTZ to serve as negative controls in order to confirm bioinequivalence. RESULTS: Whereas the reference was found to be bioequivalent when compared to itself, the creams containing 0.56% and 0.95% MTZ (negative controls) were not bioequivalent (bioinequivalent). Furthermore, another product containing 0.75% MTZ was also assessed and was found to be bioequivalent to the reference product. In addition, the use of both forearms of each participant offered an important advantage of significantly reducing the number of human subjects required to demonstrate BE with a high statistical power of > 80%. CONCLUSION: The data obtained provides compelling evidence that the developed TS method has the potential to be a cost-effective surrogate alternative for lengthy and expensive clinical trials. Consequently, its application can facilitate faster development of generic products which would, in turn, lower the economic burden of healthcare.

Topical pharmacokinetics of brinzolamide suspensions in rabbits and variability analysis for sample size and design considerations.

Identifying critical attributes for complex locally acting ophthalmic formulations and establishing in vitro-in vivo correlations can facilitate selection of appropriate thresholds for formulation changes that reflect lack of impact on in vivo performance. In this study the marketed antiglaucoma product Azopt® (1% brinzolamide suspension) and five other brinzolamide formulations varying in particle size distributions and apparent viscosities were topically administered in rabbits, and their ocular pharmacokinetics was determined in multiple ocular tissues. Statistical evaluation with ANOVA showed no significant differences between the formulations in the peak drug concentration (Cmax) in the aqueous humor and iris-ciliary body. As a post-hoc analysis, the within animal and total variability was determined for Cmax in the aqueous humor and iris-ciliary body. Based on the observed variability, we investigated the sample size needed for two types of study designs to observe statistically significant differences in Cmax. For the sample size calculations, assuming both 25% and 50% true differences in Cmax between two formulations, two study designs were compared: paired-eye dosing design (one formulation in one eye and another formulation in the other eye of the same animal at the same time) versus parallel-group design. The number of rabbits needed in the paired-eye dosing design are much lower than in the parallel-group design. For example, when the true difference in aqueous humor Cmax is 25%, nine rabbits are required in the paired-eye design versus seventy rabbits (35 per treatment) in the parallel-group design to observe a statistically significant difference with a power of 80%. Therefore, the proposed paired-eye dosing design is a viable option for the design of pharmacokinetic studies comparing ophthalmic products to determine the impact of formulation differences.

Application of Emax model to assess the potency of topical corticosteroid products.

The objective of this study was to compare the potencies of two topical corticosteroid products (TCPs) using the Emax model to fit the skin blanching responses obtained from the US FDA's vasoconstrictor assay (VCA) and to illustrate the influence of formulation on potency. The potencies of two marketed TCPs, Dermovate® cream containing clobetasol propionate (CP) and Elocon® cream containing mometasone furoate (MF), were assessed using healthy human subjects. In order to investigate the influence of formulation and associated vehicle properties, the creams were compared with their respective topical corticosteroids (TCs) from a previously published study wherein the inherent potencies of those TCs were assessed using a validated VCA method. Whereas the inherent potency of MF (Emax = -94.45 ± 0.21) was found to be greater than CP (Emax = -58.80 ± 15.65), when formulated as creams, the TCP containing CP had a higher potency (Emax = -86.15 ± 0.17) than that containing MF (Emax = -42.61 ± 26.04). This reversal of potency may be attributed to the effect of formulation factors. The comparison of the potencies of TCPs with inherent potencies of their corresponding TCs confirmed the influence of formulation parameters on the potency of those products.

Correction: Zvidzayi et al. A Novel Approach to Assess the Potency of Topical Corticosteroids. Pharmaceutics 2021, 13, 1456.

In the original publication [...].

Bioequivalence of topical clotrimazole formulations: an improved tape stripping method.

PURPOSE: Investigations were carried out to assess the use of tape stripping (TS) for the determination of bioequivalence of topical products containing 1% clotrimazole. METHODS: The study design involved the establishment of an appropriate application time, which was determined by conducting a dose duration study. Subsequently, two bioequivalence studies were conducted: i) using the brand (Canesten Topical - 1% clotrimazole cream) as both the test and the reference product and ii) comparing Canesten cream with a gel product containing the same concentration of clotrimazole (1%). Each tape strip was individually analyzed for clotrimazole content using an HPLC method and Transepidermal Water Loss (TEWL) measurements were used to normalize the stratum corneum thicknesses between subjects. RESULTS: The results of the TS investigations showed that, if the study is sufficiently powered, tape stripping may be used to determine bioequivalence according to the conventional bioequivalence limits of 0.8-1.25, as well as detect formulation differences between different clotrimazole products. CONCLUSIONS: The data from this study provided compelling evidence that tape stripping has the necessary attributes and potential to be used as a tool for the bioequivalence assessment of topical clotrimazole and/or other topical formulations, thereby circumventing the need to undertake expensive and time-consuming clinical trials for such products. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

A Novel Approach to Assess the Potency of Topical Corticosteroids.

The potencies of topical corticosteroid products have mainly been classified using clinical data but in some instances, the US Food and Drug Administration's (FDA's) vasoconstrictor assay (VCA) to assess the skin blanching response has also been used. However, the reported skin blanching response data were often based on a single visual reading and lack information on the dose (amount/quantity) or dose duration. Although several lists classifying potencies of various topical corticosteroid products have been published, the inherent potencies of topical corticosteroid raw materials used as active pharmaceutical ingredients (APIs) have not been investigated. The objective was to rank the inherent potencies of topical corticosteroid APIs and to standardize dosing such that the relevant compounds could be compared on a normalized molar basis. The potencies of clobetasol propionate, halcinonide, mometasone furoate, and fluocinolone acetonide were compared using the resulting Emax data following the fitting of the relevant response data to the Emax model where mometasone furoate > fluocinolone acetonide = clobetasol propionate > halcinonide. This ranking lists the respective inherent potencies of the APIs, which will facilitate the choice of a suitable candidate for incorporation into an appropriate topical corticosteroid product for a specific clinical indication.

A pharmacokinetic analysis of diclofenac potassium soft-gelatin capsule in patients after bunionectomy.

The clinical utility of diclofenac potassium, a nonsteroidal anti-inflammatory drug, may be lessened by inconsistent gastrointestinal absorption. Diclofenac potassium liquid filled soft-gelatin capsule (DPSGC) is an investigational formulation that uses ProSorb dispersion technology to facilitate rapid and consistent gastrointestinal absorption. In this study, the pharmacokinetic (PK) properties of DPSGC are investigated and compared with a commercially available oral diclofenac potassium tablet in patients after primary unilateral first metatarsal bunionectomy. In an open-label, randomized study, 53 patients received ProSorb-D 12.5 mg (the liquid equivalent of DPSGC), DPSGC 25 mg, DPSGC 50 mg, or immediate-release diclofenac potassium 50-mg tablet administered every 8 hours for a 24-hour inpatient period followed by 7 days of outpatient dosing. Diclofenac steady-state PK was evaluated over an 8-hour sampling period 4 days after surgery. Delayed and/or multiple peaks in the diclofenac plasma concentration-time course profiles occurred more frequently with the commercially available oral diclofenac potassium 50-mg tablet than with the other DPSGC formulations. PK data for ProSorb-D 12.5-mg liquid, DPSGC 25 mg, DPSGC 50 mg, and diclofenac potassium 50-mg tablet revealed mean peak plasma concentrations (Cmax) of 302, 749, 1006, and 902 ng/mL, respectively, whereas area under the plasma concentration curve values were 316, 595, 1029, and 1166 ng-hour/mL, respectively. Mean times to Cmax (tmax) were 0.49, 0.63, 0.95, and 1.26 h, respectively. When compared with absorption characteristics of diclofenac potassium 50-mg tablet, DPSGC was more rapidly and consistently absorbed after bunionectomy. These characteristics should be advantageous when rapid pain relief is desired.

Pharmacokinetics and Bioequivalence of Branded and Generic Formulations of Dofetilide 0.5-mg Capsules After Single-Dose Administration in Healthy Subjects.

Class III antiarrhythmics are preferred therapy for managing atrial fibrillation/flutter. Dofetilide 0.5-mg capsules were US Food and Drug Administration (FDA) approved in 1999 to treat atrial fibrillation/flutter. Bioequivalence of generic dofetilide is important for treating arrhythmias because drug concentrations must be consistent to maintain normal sinus rhythm. Generic dofetilide 0.5-mg capsule pharmacokinetics were compared with branded product in 2 open-label, 2-way crossover, single-dose studies - 1 study each in fasted and fed healthy subjects. Blood samples were collected before and up to 48 hours after dosing. Safety was assessed by tabulating adverse events and vital signs. Seventy-three subjects were enrolled; 59 completed the studies. In fasted subjects, the 90% confidence intervals (CIs) for generic dofetilide 0.5 mg versus the reference formulation were 0.996-1.026 for the area under the plasma concentration-time curve from 0 to infinity (AUC) and 0.974-1.066 for the maximum observed concentration (Cmax ). In fed subjects, the 90%CIs for AUC and Cmax were 0.988-1.015 and 0.928-0.992, respectively. All ratios were within the FDA-established bioequivalence range. Twenty-six subjects experienced 37 adverse events (generic, 15; reference, 22); all but 1 were mild or moderate in severity. Generic dofetilide 0.5-mg capsules can be considered bioequivalent to the reference product.

Humanized monoclonal antibody armanezumab specific to N-terminus of pathological tau: characterization and therapeutic potency.

BACKGROUND: The experience from clinical trials indicates that anti-Aß immunotherapy could be effective in early/pre-clinical stages of AD, whereas at the late stages promoting the clearing of Aß alone may be insufficient to halt the disease progression. At the same time, pathological tau correlates much better with the degree of dementia than Aß deposition. Therefore, targeting pathological tau may provide a more promising approach for the treatment of advanced stages of AD. Recent data demonstrates that the N-terminal region of tau spanning aa 2-18 termed "phosphatase activation domain" that is normally hidden in the native protein in 'paperclip'-like conformation, becomes exposed in pathological tau and plays an essential role in the inhibition of fast axonal transport and in aggregation of tau. Hence, we hypothesized that anti-Tau2-18 monoclonal antibodies (mAb) may recognize pathological, but not normal tau at very early stages of tauopathy and prevent or decrease the aggregation of this molecule. METHODS: Mouse mAbs were generated using standard hybridoma methodology. CDR grafting was used for humanization of mouse mAb. Humanized mAb (Armanezumab) was characterized and tested in vitro/ex vivo/in vivo using biochemical and immunological methods (HPLC, Biacore, ELISA, IHC, FRET, etc.). Stable DG44 cell line expressing Armanezumab was generated by clone selection with increased concentrations of methotrexate (MTX). RESULTS: A panel of mouse mAbs was generated, clone 1C9 was selected based on binding to pathological human tau with high affinity and humanized. Fine epitope mapping revealed conservation of the epitope of human tau recognized by the parent murine mAb and Armanezumab. Importantly, Armanezumab (i) bound to tau with high affinity as determined by Biacore; (ii) bound pathological tau in brains from AD, FTD and Pick's disease cases; (iii) inhibited seeding effect of aggregated tau from brain lysate of P301S Tg mice; (iv) inhibited cytotoxic effect of tau oligomers; (v) reduced total tau (HT7) and AT100, PHF1, AT8, AT180, p212, p214-positive tau species in brains of tau transgenic mice after intracranial injection. A stable CHO cell line producing >1.5 g/l humanized mAb, Armanezumab was generated. CONCLUSION: These findings suggest that Armanezumab could be therapeutic in clinical studies for treatment of AD.

The use of an imagery mnemonic to teach the Krebs cycle.

The Krebs Cycle is a highly taught biochemical pathway that is traditionally difficult to learn. Twenty-seven undergraduate students were randomized to a rote memorization arm or to a mnemonic arm. They were given a pre-test, then shown a lecture corresponding to their assigned method, and then given an immediate Week 0 post-test and a Week 4 post-test. Groups scored comparably low on the pre-test (p = 0.7113). Students in the mnemonic arm performed better on the Week 0 post-test than those using rote (p = 0.0055). By Week 4, there was evidence of knowledge decay, with both arms' having comparably low scores (mnemonic vs. rote, p = 0.3739). The mnemonic assists in rapid acquisition of knowledge but probably has to be reviewed iteratively over time to demonstrate its full potential over rote memorization. A limited number of students from only one school was used. © 2016 by The International Union of Biochemistry and Molecular Biology, 44:224-229, 2016.

Pharmacokinetics of the first combination 17ß-estradiol/progesterone capsule in clinical development for menopausal hormone therapy.

OBJECTIVE: This study aims to compare the pharmacokinetics and oral bioavailability of a capsule combining 17ß-estradiol and progesterone in a non-peanut oil-containing formulation with those of widely used and approved separate formulations of estradiol and progesterone coadministered to healthy postmenopausal women. METHODS: This was an open-label, balanced, randomized, single-dose, two-treatment, three-period, three-sequence, cross-over, partial-replicate, reference-scaled study. Postmenopausal women (aged 40-65 y) were randomly assigned to one of three dosing sequences of test and reference products (TRR, RTR, or RRT, where T is the test drug and R is the coadministered reference product), with each of the three periods separated by a 14-day washout. The primary pharmacokinetic endpoints were Cmax, AUC(0-t), and AUC(0-inf) for the test and reference products, assessed for bioequivalence using the scaled average bioequivalence or unscaled average bioequivalence method. Safety was assessed by clinical observation, participant-reported adverse events, and laboratory data, including blood levels of hormones. RESULTS: Sixty-six women were randomly assigned, and 62 women (94.0%) completed all three study periods. All AUC and Cmax parameters met bioequivalence criteria for all analytes (estradiol, progesterone, and estrone), except Cmax for total estrone. The extent of estradiol and progesterone absorption was similar between the test product and the reference products. Four adverse events--all considered mild and unrelated to the study drugs--were reported. CONCLUSIONS: The combination 17ß-estradiol/progesterone product demonstrates bioavailability similar to those of the respective reference products of estradiol and progesterone. If regulatory approval is obtained, this new hormone therapy would be the first treatment of menopause symptoms to combine progesterone with 17ß-estradiol in an oral formulation.

Analgesic safety and efficacy of diclofenac sodium softgels on postoperative third molar extraction pain.

PURPOSE: The purpose of this single-blind, placebo-controlled, 3-arm parallel, randomized study was to compare the analgesic efficacy and tolerability of a single dose of 100 mg diclofenac potassium (Cataflam; Novartis, Stein, Switzerland), 100 mg diclofenac sodium softgel, and placebo in patients experiencing moderate to severe postoperative pain after third molar extraction. PATIENTS AND METHODS: Seventy-five patients (67% female with a mean age of 23, age range 18 to 34.5 years) participated in the study following removal of at least 1 impacted mandibular third molar. Patients received a single dose of study medication when their postoperative pain reached a moderate or severe intensity. Analgesic efficacy measures included the time to meaningful pain relief measured using a stopwatch and time to rescue medication. Pain relief (PR) and Pain intensity (PI) ratings were recorded at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 8, and 24 hours postdosing. Summary analgesic measures, including Summed Pain Relief Score (TOTPAR) and Summed Pain Intensity Differences (SPID), were calculated from the 0.25- to 6-hour responses. The time between pain relief and rescue and a global evaluation for the effectiveness of the study medications were recorded at the end of the study. Seven scheduled blood samples were collected from each patient for determining plasma concentrations of diclofenac anion. RESULTS: Both diclofenac sodium softgel and Cataflam were significantly more effective than placebo (P <.0001) for all summary analgesic measures. The average overall pain relief was substantially better from diclofenac sodium softgel than from Cataflam, but the difference was not statistically significant (P =.14). In patients taking diclofenac sodium softgel, 50% of the patients experienced a time to onset of analgesic activity within 18 minutes and the median analgesic duration was 5 hours (302 minutes). Fifty percent of the patients taking Cataflam had a time to onset of action within 38 minutes, and the median duration of analgesia was 4.5 hours (272 minutes). At the time of rescue drug administration or 6 hours, whichever was earlier, 72% of the patients given diclofenac sodium softgel rated the medication as a very good or excellent pain reliever, whereas only 45% of the patients taking Cataflam gave these ratings. No serious adverse events were observed in this study. The mean concentrations of diclofenac from the diclofenac sodium softgel formulation were significantly different from the Cataflam formulation. The mean C(max) for the softgel was almost twice that of Cataflam and C(max) was reached an hour earlier, on average. CONCLUSIONS: More diclofenac anion was absorbed at a quicker rate using the formulation diclofenac sodium softgel 100 mg than Cataflam. The softgel provided a very rapid onset of analgesic activity, a prolonged analgesic duration, and an acceptable side-effect profile in the postoperative third molar surgery pain model. In an acute pain situation, the rapid absorption of nonsteroidal anti-inflammatory drugs from a formulation like the Softgel may positively affect the time of onset and duration of inflammatory pain compared with other commercially available nonsteroidal anti-inflammatory drug formulations.