BackgroundThe extents of generic-reference and generic-generic average bioequivalence and intra-subject variation of on-market drug products have not been prospectively studied on a large scale.MethodsWe assessed bioequivalence of 42 generic products of 14 immediate-release oral drugs with the highest number of generic products on the Saudi market. We conducted 14 four-sequence, randomized, crossover studies on the reference and three randomly-selected generic products of amlodipine, amoxicillin, atenolol, cephalexin, ciprofloxacin, clarithromycin, diclofenac, ibuprofen, fluconazole, metformin, metronidazole, paracetamol, omeprazole, and ranitidine. Geometric mean ratios of maximum concentration (Cmax) and area-under-the-concentration-time-curve, to last measured concentration (AUCT), extrapolated to infinity (AUCI), or truncated to Cmax time of reference product (AUCReftmax) were calculated using non-compartmental method and their 90% confidence intervals (CI) were compared to the 80.00%–125.00% bioequivalence range. Percentages of individual ratios falling outside the ±25% range were also determined.ResultsMean (SD) age and body-mass-index of 700 healthy volunteers (28–80/study) were 32.2 (6.2) years and 24.4 (3.2) kg/m2, respectively. In 42 generic-reference comparisons, 100% of AUCT and AUCI CIs showed bioequivalence, 9.5% of Cmax CIs barely failed to show bioequivalence, and 66.7% of AUCReftmax CIs failed to show bioequivalence/showed bioinequivalence. Adjusting for 6 comparisons, 2.4% of AUCT and AUCI CIs and 21.4% of Cmax CIs failed to show bioequivalence. In 42 generic-generic comparisons, 2.4% of AUCT, AUCI, and Cmax CIs failed to show bioequivalence, and 66.7% of AUCReftmax CIs failed to show bioequivalence/showed bioinequivalence. Adjusting for 6 comparisons, 2.4% of AUCT and AUCI CIs and 14.3% of Cmax CIs failed to show bioequivalence. Average geometric mean ratio deviation from 100% was ≤3.2 and ≤5.4 percentage points for AUCI and Cmax, respectively, in both generic-reference and generic-generic comparisons. Individual generic/reference and generic/generic ratios, respectively, were within the ±25% range in >75% of individuals in 79% and 71% of the 14 drugs for AUCT and 36% and 29% for Cmax.ConclusionsOn-market generic drug products continue to be reference-bioequivalent and are bioequivalent to each other based on AUCT, AUCI, and Cmax but not AUCReftmax. Average deviation of geometric mean ratios and intra-subject variations are similar between reference-generic and generic-generic comparisons.Trial registration ClinicalTrials.gov identifier: NCT01344070 (registered April 3, 2011).Electronic supplementary materialThe online version of this article (doi:10.1186/s40360-017-0182-1) contains supplementary material, which is available to authorized users.

BackgroundConventional randomized placebo-controlled study design assumes the absence of drug*placebo interaction. We hypothesized the presence of such an interaction and that conventionally estimated drug effect might be biased. The objectives of the study were to determine the drug*placebo interaction effect (main) and compare conventionally estimated and interaction model-estimated drug effects (secondary).MethodsWe used a hybrid of balanced placebo and randomized placebo-controlled designs. Four hundred eighty healthy volunteers were randomized to three groups. The first received hydroxyzine (25 mg) described as hydroxyzine or placebo, the second received placebo described as hydroxyzine or placebo, and the third received hydroxyzine and placebo described as unknown; each in a randomized crossover design. Seven participants failed to crossover. Group assignment was concealed from participants and study coordinators. Coordinators were blinded to group and intervention assignment. Participants and coordinators were deceived as to study objectives. Main outcomes were mean area-under-the-curve of drowsiness (therapeutic outcome) and mouth-dryness (adverse outcome), self-reported on 100 mm visual analog scale over 7 h. Drug, placebo, placebo + interaction, and total effects were estimated using analysis of covariance by comparing received hydroxyzine/told placebo to received placebo/told placebo, received placebo/told hydroxyzine to received placebo/told placebo, received hydroxyzine/told hydroxyzine to received hydroxyzine/told placebo, and received hydroxyzine/told hydroxyzine to received placebo/told placebo, respectively. Drug effect was also conventionally estimated in the third group.ResultsMean (SD) age was 31.4 (6.6) years, 65% were males. There was significant difference between placebo + interaction effect and placebo effect for both drowsiness and mouth-dryness with a mean difference (95% confidence interval) of 35.1 (5.6 to 64.6) and 23.8 (2.4 to 45.2) mm*hr, respectively. Total effect was larger than the sum of drug and placebo effects for drowsiness (139.7 (109.8 to 169.6) vs. 99.1 (68.2 to 130.0) mm*hr) and mouth-dryness (63.6 (41.1 to 86.1) vs. 34.7 (11.1 to 58.4) mm*hr). Conventionally estimated drug effect was larger than interaction model-estimated drug effect for drowsiness (69.2 (45.5 to 92.8) vs. (58.3 (31.6 to 85.0) mm*hr) and mouth-dryness (19.9 (5.3 to 34.5) vs. 9.5 (−9.2 to 28.1) mm*hr).ConclusionsThere is significant and important drug*placebo interaction effect that may bias conventionally estimated drug effect.Trial registrationClinicalTrial.gov identifier: NCT01501591 (registered December 25, 2011).

Background Substituted judgment assumes adequate knowledge of patient’s mind-set. However, surrogates’ prediction of individual healthcare decisions is often inadequate and may be based on shared background rather than patient-specific knowledge. It is not known whether surrogate’s prediction of patient’s integrative life-story narrative is better. Methods Respondents in 90 family pairs (30 husband-wife, 30 parent-child, 30 sibling-sibling) rank-ordered 47 end-of-life statements as life-story narrative measure (Q-sort) and completed instruments on decision-control preference and healthcare-outcomes acceptability as control measures, from respondent’s view (respondent-personal) and predicted pair’s view (respondent-surrogate). They also scored their confidence in surrogate’s decision-making (0 to 4 = maximum) and familiarity with pair’s healthcare-preferences (1 to 4 = maximum). Life-story narratives’ prediction was examined by calculating correlation of statements’ ranking scores between respondent-personal and respondent-surrogate Q-sorts (projection) and between respondent-surrogate and pair-personal Q-sorts before (simulation) and after controlling for correlation with respondent-personal scores (adjusted-simulation), and by comparing percentages of respondent-surrogate Q-sorts co-loading with pair-personal vs. respondent-personal Q-sorts. Accuracy in predicting decision-control preference and healthcare-outcomes acceptability was determined by percent concordance. Results were compared among subgroups defined by intra-pair relationship, surrogate’s decision-making confidence, and healthcare-preferences familiarity. Results Mean (SD) age was 35.4 (10.3) years, 69% were females, and 73 and 80% reported ≥ very good health and life-quality, respectively. Mean surrogate’s decision-making confidence score was 3.35 (0.58) and 75% were ≥ familiar with pair’s healthcare-preferences. Mean (95% confidence interval) projection, simulation, and adjusted-simulation correlations were 0.68 (0.67–0.69), 0.42 (0.40–0.44), and 0.26 (0.24–0.28), respectively. Out of 180 respondent-surrogate Q-sorts, 24, 9, and 32% co-loaded with respondent-personal, pair-personal, or both Q-sorts, respectively. Accuracy in predicting decision-control preference and healthcare-outcomes acceptability was 47 and 52%, respectively. Surrogate’s decision-making confidence score correlated with adjusted-simulation’s correlation score (rho = 0.18, p = 0.01). There were significant differences among the husband-wife, parent-child, and sibling-sibling subgroups in percentage of respondent-surrogate Q-sorts co-loading with pair-personal Q-sorts (38, 32, 55%, respectively, p = 0.03) and percent agreement on healthcare-outcomes acceptability (55, 35, and 67%, respectively, p = 0.002). Conclusions Despite high self-reported surrogate’s decision-making confidence and healthcare...