Evaluation of truncated areas in the assessment of bioequivalence of immediate release formulations of drugs with long half-lives and of Cmax with different dissolution rates

Bioequivalence Assessment of an Oral Fixed-Dose Formulation of Dutasteride-Tamsulosin 0.5 mg/0.4 mg: A Randomized, Single-Blind, Single-Dose, 2-Period Crossover Study in Mexican Population Under Fasted Conditions

The aim of the present study was to compare the bioavailability and to demonstrate the bioequivalence between a dutasteride-tamsulosin 0.5 mg/0.4 mg capsule formulation and the regulatory reference drug (Combodart®, GlaxoSmithKline). A randomized, single-blind, single-dose, 2-way crossover study under fasting conditions, with at least a 28-day washout period was carried out in healthy volunteers. Plasma concentrations of drugs were determined by high-performance liquid chromatography-tandem mass spectrometry. The pharmacokinetic analysis included maximum plasma concentration (C_max ), area under the plasma concentration-time curve (AUC) from time 0 to 72 hours, and AUC from baseline to infinity. The test formulation was considered bioequivalent if the geometric mean ratios (test/reference) were within the predetermined range of 80% to 125%. Safety and tolerability were evaluated by clinical assessment. The confidence intervals for the log-transformed test/reference ratios for dutasteride, C_max (95.4-109.2) and AUC from baseline to 72 hours (93.2-109.1), and for tamsulosin, C_max (101.9-119.8), AUC from baseline to the last quantifiable concentration (91.4-106.3) and AUC from baseline to infinity (90.9-103.3), were within the allowed limit specified by the regulatory authorities (80%-125%). In addition, both test and reference drugs were safe and tolerated. These results demonstrated the bioequivalence of test product (Dakart®) compared with Combodart®.

Determination of amlodipine, indapamide and perindopril in human plasma by a novel LC-MS/MS method: Application to a bioequivalence study

A robust and rapid UPLC-MS/MS method has been developed, optimized and validated for determination of amlodipine (AML), indapamide (IND) and perindopril (PRN) in human plasma. A positive electrospray ionization mode was used in a Xevo TQD LC-MS/MS instrument. A single sample preparation step using extraction technique was applied to extract the three analytes from plasma samples. There was no need to extract indapamide from blood samples in a further step. Extraction of the three drugs and internal standards was done using a solvent mixture composed of methyl tertiary butyl ether, dichloromethane and ethyl acetate. The prepared samples were analyzed using an Acquity UPLC HSS C₁₈ (100 × 2.1 mm, 1.7 μm) column. Ammonium acetate and methanol, pumped at a flow rate of 0.3 ml/min, were used as a mobile phase. Method validation was done as per the US Food and Drug Administration guidelines. Linearity was achieved in the range of 0.2-15 ng/ml for AML, 0.5-50 ng/ml for IND and 0.5-120 ng/ml for PRN. Accuracy and precision were estimated and found to be within the acceptable ranges. The rapid chromatography permits analysis of many samples per batch, making the method suitable for clinical and pharmacokinetic investigations. The developed and validated method was applied to estimate AML, IND, and PRN in a fasting bioequivalence study in healthy human volunteers.

Quantification of sofosbuvir and ledipasvir in human plasma by UPLC-MS/MS method: Application to fasting and fed bioequivalence studies

A rapid and sensitive LC-MS/MS method was developed, optimized and validated for quantification of sofosbuvir (SF) and ledipasvir (LD) in human plasma using eplerenone as an internal standard (IS). Analytes and IS were extracted from plasma by simple liquid-liquid extraction technique using methyl tertiary butyl ether. The prepared samples were chromatographed on Acquity UPLC BEH C18 column. Separation was done using a mobile phase formed of 0.1% formic acid and acetonitrile (50:50, v/v) in an isocratic mode at a flow rate of 0.4ml/min. The Xevo TQD LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. A full validation of the method was performed according to the FDA guidelines. Linearity was found to be in the range of 0.25-3500ng/ml for SF and 5-2000ng/ml for LD. The intra-day and inter-day precision and accuracy results were within the acceptable limits. A short run time of 2min allows analysis of more than 400 plasma samples per day. The developed method was successfully applied to both fasting and fed bioequivalence studies in healthy human volunteers.

Sex-by-formulation interaction assessed through a bioequivalence study of efavirenz tablets

Although sex-related differences in gastrointestinal physiology have been vastly reported, its impact on drug oral bioavailability and bioequivalence (product discrimination) is often ignored. On this work results from an average bioequivalence study between tablets containing 600mg of the antiretroviral efavirenz (EFV), carried out with 14 healthy subjects (8 female and 6 men) in a randomized 2-period, 2-treatment crossover design, are analyzed from a sex-based approach. Sequences were balanced within each sex group. Considering all subjects, no differences were observed on EFV absorbed amount, as shown by the estimated 90CI of the AUC96 Test/Reference bioequivalence ratio (T/R): 0.950-1.05. However, results were not conclusive due to the 90CI for CMAX T/R was 0.743-1.07. Over this parameter, a significant sex-by-formulation interaction was detected: 90CI CMAX T/R was 0.838-1.36 in women and 0.540-0.920 in men; with a 52% relative difference between point estimates. Formulation differences were therefore evidenced only by male subjects. In vitro dissolution and disintegration tests for both products were carried out in two aqueous media: A) SLS 0.25% and B) HCl/KCl pH1.2. T/R results for dissolution efficiency and tablet disintegration times of formulations in both A and B media were highly correlated with CMAX T/R bioequivalence results observed in women and men respectively, showing that a dissimilar gastrointestinal environment between sexes affected EFV oral absorption. This work shows how sex-by-formulation interaction can affect bioequivalence conclusions. Sex effect on product discrimination should be specially disclosed in bioequivalence studies, mainly for drugs aimed to be given to both sexes.

Development of a sensitive UPLC-ESI-MS/MS method for quantification of sofosbuvir and its metabolite, GS-331007, in human plasma: Application to a bioequivalence study

A rapid and simple LC-MS/MS method was developed and validated for the simultaneous estimation of sofosbuvir (SF) and its metabolite GS-331007 (GS) using famotidine as an internal standard (IS). The Xevo TQD LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. Extraction with ethyl acetate was used in sample preparation. The prepared samples were chromatographed on Acquity UPLC HSS C₁₈ (50 mm × 2.1 mm, 1.8 μm) column by pumping 0.1% formic acid and acetonitrile (50:50, v/v) in an isocratic mode at a flow rate of 0.3 ml/min. Method validation was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 10-2500 ng/ml for both SF and its metabolite. The intra-day and inter-day precision and accuracy results were within the acceptable limits. A very short run time of 1.2 min made it possible to analyze more than 300 human plasma samples per day. The developed assay method was successfully applied to a bioequivalence study in human volunteers.

Bioequivalence of long half-life drugs--informative sampling determination--using truncated area in parallel-designed studies for slow sustained-release formulations

A simulation study was done to determine if 72 h is the most informative sampling duration for bioequivalence (BE) determination in parallel-designed BE studies with drugs that have half-lives of at least 30 h. The impact of absorption and elimination half-lives on informative sampling was evaluated. Two-treatment parallel-designed BE studies using a one-compartment oral absorption model with half-lives of 30 and 350 h was simulated. Area under the curve (AUC) values were truncated at 12-360 h. Experimental BE data [median time to reach the maximum concentration (T(max) ) = 20 h and low clearance = 0.192 L/h) indicated a decrease and then an increase in the intrasubject variability [root mean square error (RMSE)] for truncated AUC as a function of time. Simulations supported these findings with the highest probability of passing the BE confidence interval criteria being between 60 and 96 h, depending on half-life and percent coefficient of variation. The 30-h simulation exhibited a minimum in RMSE at 24-h truncation that continued to increase up to 360 h, whereas the 350-h simulation exhibited a minimum at 60 h, which increased after 96 h. Power curves at the 350-h half-life showed higher probabilities of rejection of BE for true test/reference ratios greater than 0.9. For parallel-designed BE studies, sampling beyond 120 h will not affect the BE decision and therefore is unnecessary.

Residual fraction of the area under the curve as a qualitative criterion in pharmacokinetic studies

The aim of the present study was to determine whether the residual area under the curve (AUC(res%); expressed as % of total value of AUC) could be used as a parameter for the qualitative evaluation of pharmacokinetic studies.We propose new criteria for the qualitative evaluation of pharmacokinetic analysis. Two sets of hypothetical data that illustrate the relationship between concentration and time were used for the analysis of drug pharmacokinetics. Non-compartmental analysis was applied for the calculations. The results obtained from the hypothetical data were compared with those obtained from an in vivo study in which 3-week-old broiler chickens were administered 10 mg/kg b.w. enrofloxacin intravenously (iv) or per os (po). In the first set of data (A-D), AUC(res%) values were as follows: A= 16.29% and B = 20.79% for iv administration and C = 29.61% and D = 27.90% for po administration. In the next set of data (E-G), AUC(res%) values after oral administration were 25.30% (E), 23.18% (F), and 20.79% (G). The AUC(res%) values after iv administration of enrofloxacin were similar to po administration; the range of iv and po administration values were 14.35% to 17.50% and 11.14% to 28.33% of the total AUC, respectively. The analysis of the hypothetical data indicates that AUC(res%) is not an optimal method for the evaluation of pharmacokinetic studies.

Operating characteristics of a partial-block randomized crossover bioequivalence study for dutasteride, a drug with a long half-life: investigation through simulation and comparison with final results

Studies to establish bioequivalence (BE) of a drug are important elements in support of drug applications. A typical BE study is conducted as a single dose, randomized, 2-period crossover design. For drugs with long half lives (≥ 48 hours) and evaluation of multiple BE objectives in 1 trial, this design may not be adequate. A parallel design may then be a more appropriate choice. However, parallel designs require increased sample size, which can become substantial. One option that is a compromise between the complete randomized block design and the parallel design is a partial-block crossover design. This approach came about during the development of a combination of dutasteride and tamsulosin. Previous experience with performing single-dose dutasteride studies suggested that 28 days of washout is needed between treatments because of its half-life of 7-9 days. Simulations were performed to assess the operating characteristics of this design using a previously developed PK model. Four scenarios were developed, and each scenario was simulated 500 times. The results showed that this design demonstrated acceptable consumer and producer risk. Partial-block crossover designs should be considered for studies when the half-life of the drug is long and there are more than 2 periods.

A SAS/IML program for simulating pharmacokinetic data

Data simulation can be an invaluable tool for optimizing the design of bioequivalence trials. It can be particularly useful when exploring alternative approaches for assessing product comparability especially in the context of encountering various complex experimental situations that can occur in veterinary medicine. With this in mind, we designed a novel SAS/IML program to generate pharmacokinetic datasets that reflect the various kinetic, population, and study design characteristics that complicate the bioequivalence evaluation of animal health products. Developing this simulation program within SAS provides an opportunity to utilize the statistical capabilities of this software platform.

Plasma concentrations of praziquantel after oral administration of single and multiple doses in loggerhead sea turtles (Caretta caretta)

OBJECTIVE

To determine the pharmacokinetics of praziquantel following single and multiple oral dosing in loggerhead sea turtles.

ANIMALS

12 healthy juvenile loggerhead sea turtles.

PROCEDURE

Praziquantel was administered orally as a single dose (25 and 50 mg/kg) to 2 groups of turtles; a multiple-dose study was then performed in which 6 turtles received 3 doses of praziquantel (25 mg/kg, PO) at 3-hour intervals. Blood samples were collected from all turtles before and at intervals after drug administration for assessment of plasma praziquantel concentrations. Pharmacokinetic analyses included maximum observed plasma concentration (Cmax), time to maximum concentration (Tmax), area under the plasma praziquantel concentration-time curve, and mean residence time (MRTt).

RESULTS

Large interanimal variability in plasma praziquantel concentrations was observed for all dosages. One turtle that received 50 mg of praziquantel/kg developed skin lesions within 48 hours of administration. After administration of 25 or 50 mg of praziquantel/kg, mean plasma concentrations were below the limit of quantification after 24 hours. In the multiple-dose group of turtles, mean plasma concentration was 90 ng/mL at the last sampling time-point (48 hours after the first of 3 doses). In the single-dose study, mean Cmax and Tmax with dose were not significantly different between doses. After administration of multiple doses of praziquantel, only MRTt was significantly increased, compared with values after administration of a single 25-mg dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of 25 mg of praziquantel/kg 3 times at 3-hour intervals may be appropriate for treatment of loggerhead sea turtles with spirorchidiasis.

Enhanced oral absorption of halofantrine enantiomers after encapsulation in a proliposomal formulation

In this study, we evaluated the ability of a coated, encapsulated formulation to increase the oral bioavailability of (+/-)-halofantrine (HF) enantiomers, a drug with low and erratic oral bioavailability. After encapsulation of HF in distearoylphosphatidylcholine, the dried particles were coated with cellulose acetate phthalate. A suspension of the product was made using methylcellulose as a dispersion agent, and the product was administered to Sprague-Dawley rats to provide a HF dose of 7 mg kg-1 as the HCl salt. HF HCl powder in 1% methylcellulose with or without liposomal product excipients was also administered to separate groups of rats, which served as control groups. Serial blood samples were obtained from the rats and plasma was assayed by stereospecific high-performance liquid chromatography. There were no significant differences in the area under the concentration-time curve (AUC) or maximum concentration (Cmax) between the two control groups. Plasma concentrations of both HF enantiomers were significantly higher in the rats given HF as an encapsulated proliposomal formulation compared with the control groups. Compared with methylcellulose control, the encapsulation product resulted in increases of 41 to 47% in the AUC of HF enantiomers, and 90 to 100% in Cmax. The ability of an encapsulated proliposomal product to significantly increase the oral absorption of HF was clearly demonstrated.

The effect of soybean oil refuse powder used as vehicle on the absorption of oxolinic acid in chickens under fasting and nonfasting conditions and the correlation with in vitro dissolution

The effect of soybean oil refuse powder (SOR) when used as a vehicle on the absorption of oxolinic acid (OXA) powder in chicken, the dissolution profile of OXA and the correlation between in vivo and in vitro study were examined. To examine in vivo bioavailability, chickens fed or fasted were studied using a 2 x 2 crossover design. The OXA was administered OXA or OXA-SOR (1 : 9) mixture 20 mg OXA/kg. In vitro dissolution rates for OXA and OXA-SOR were measured using the paddle (PD) and the rotatory dialysis cell dissolution (PTSW) methods. Maximum plasma concentration (Cmax) and area under the curve (AUC) were significantly increased by the addition of SOR to OXA. Differences between OXA and OXA-SOR were more remarkable under fasted as compared with fed condition. In vitro dissolution rates of OXA-SOR pH 1.2, 6.5 and 7.2 as determined by the PD and the PTSW methods were increased in the presence of SOR vehicle. Differences between OXA and OXA-SOR in vitro dissolution rates were greater than in vivo bioavailability. Correlation between in vitro release (%) and in vivo absorption (%) showed good linearity (gamma=0.8805-0.9999).

Product equivalence study comparing the tolerability, pharmacokinetics, and pharmacodynamics of various human immunoglobulin-G formulations

In this randomized, double-blind, parallel-group study, a commercially available human immunoglobulin-G product, IVIG, was compared with two test formulations: (1) IVIG-N, which is a nanofiltered formulation of IVIG, and (2) IVIG-L, which is a nanofiltered, liquid, ready-for-use IgG formulation containing nicotinamide, L-proline, and L-isoleucine as stabilizers. Three groups of 10 healthy subjects each received a single 0.6 g/kg dose of one of the formulations infused over 3.5 to 6.8 hours, depending on the total volume to be infused. Blood samples were obtained over a 6-week period to assess pharmacokinetics, immunogenicity, and the pharmacodynamic effects on leukocytes and TNF-alpha. A blood sample was taken at 6 months for a viral safety check. Administrations were generally well tolerated with only one reference IVIG infusion stopped prematurely due to headache. The IgG Cmax and AUC over the 6-week blood sampling period from both test formulations satisfied equivalence criteria compared with the reference formulation. In subjects receiving IVIG-L, peak concentrations of the stabilizer nicotinamide ranged from 0.34 to 0.47 mmol/L and of nicotinamide-N-oxide from 0.03 to 0.04 mmol/L, which are below those reported to cause adverse events. During the infusion of IVIG, leukocyte counts initially declined from a baseline of 5.7 +/- 1.1 x 10(9)/L to 3.7 +/- 0.8 x 10(9)/L at 2 to 4 hours and returned to baseline by 24 hours. TNF-alpha levels, reflecting activation of the monocyte-macrophage system by the infused IVIG, rose from a baseline of 13 +/- 4 pg/mL to a peak of 272 +/- 324 pg/mL at 2 to 4 hours and returned to baseline by 24 hours. These patterns were generally similar for the test formulations, with the exception that the increase in TNF-alpha levels was dampened for IVIG-N, although this was not statistically significant. There was no evidence of immunogenicity or viral transmission from any of the formulations. Hence, these three formulations were generally well tolerated, yielded similar systemic exposure to IgG over a 6-week period after administration, and did not give rise to immunogenicity or viral safety concerns.