Review of the Reported Measures of Clinical Validity and Clinical Utility as Arguments for the Implementation of Pharmacogenetic Testing: A Case Study of Statin-Induced Muscle Toxicity.

Advances from pharmacogenetics (PGx) have not been implemented into health care to the expected extent. One gap that will be addressed in this study is a lack of reporting on clinical validity and clinical utility of PGx-tests. A systematic review of current reporting in scientific literature was conducted on publications addressing PGx in the context of statins and muscle toxicity. Eighty-nine publications were included and information was selected on reported measures of effect, arguments, and accompanying conclusions. Most authors report associations to quantify the relationship between a genetic variation an outcome, such as adverse drug responses. Conclusions on the implementation of a PGx-test are generally based on these associations, without explicit mention of other measures relevant to evaluate the test's clinical validity and clinical utility. To gain insight in the clinical impact and select useful tests, additional outcomes are needed to estimate the clinical validity and utility, such as cost-effectiveness.

Potential association between the recent increase in campylobacteriosis incidence in the Netherlands and proton-pump inhibitor use - an ecological study.

The Netherlands saw an unexplained increase in campylobacteriosis incidence between 2003 and 2011, following a period of continuous decrease. We conducted an ecological study and found a statistical association between campylobacteriosis incidence and the annual number of prescriptions for proton pump inhibitors (PPIs), controlling for the patient's age, fresh and frozen chicken purchases (with or without correction for campylobacter prevalence in fresh poultry meat). The effect of PPIs was larger in the young than in the elderly. However, the counterfactual population-attributable fraction for PPIs was largest for the elderly (ca 45% in 2011) and increased at population level from 8% in 2004 to 27% in 2011. Using the regression model and updated covariate values, we predicted a trend break for 2012, largely due to a decreased number of PPI prescriptions, that was subsequently confirmed by surveillance data. Although causality was not shown, the biological mechanism, age effect and trend-break prediction suggest a substantial impact of PPI use on campylobacteriosis incidence in the Netherlands. We chose the ecological study design to pilot whether it is worthwhile to further pursue the effect of PPI on campylobacteriosis and other gastrointestinal pathogens in prospective cohort studies. We now provide strong arguments to do so.

On the formation of bromhexine impurity E and its chromatographic behaviour.

An unknown bromhexine hydrochloride (BRH) degradation product in BRH oral solutions (finished products) was potentially related to the purity of this API. Several degradation experiments were conducted and its identity and formation were investigated using LC-DAD and LC-DAD-MS/MS. Using the LC method described in the Ph.Eur monograph BRH the degradation product was observed at RRTBRH 0.1 and the specified impurities A-D were ruled out as candidates. Impurity E was initially not considered as a candidate as EDQM reported an expected RRTBRH of 1.8. Still, the LC-DAD-MS/MS results were consistent with the M+ ion for impurity E and its expected fragment ions. Therefore, standard addition was carried out using the Ph. Eur. method which confirmed that the degradation product at RRT 0.1 was impurity E. Upon changing the column type to a column described in the knowledge database, impurity E eluted at an RRT of 1.5. Nevertheless, both columns met all of the criteria in the monograph. The formation of impurity E was even observed in BRH solutions without added reagents. As the conversion from BRH to impurity E requires a source of carbon, we suggest that one BRH molecule degrades through a radical mechanism to a reactive species which subsequently is quenched by another BRH molecule producing impurity E. We suggest the transparency list for BRH to be more explicit on the formation of impurity E, its RRT and the permissible LC columns.

Consistency of FMEA used in the validation of analytical procedures.

In order to explore the consistency of the outcome of a Failure Mode and Effects Analysis (FMEA) in the validation of analytical procedures, an FMEA was carried out by two different teams. The two teams applied two separate FMEAs to a High Performance Liquid Chromatography-Diode Array Detection-Mass Spectrometry (HPLC-DAD-MS) analytical procedure used in the quality control of medicines. Each team was free to define their own ranking scales for the probability of severity (S), occurrence (O), and detection (D) of failure modes. We calculated Risk Priority Numbers (RPNs) and we identified the failure modes above the 90th percentile of RPN values as failure modes needing urgent corrective action; failure modes falling between the 75th and 90th percentile of RPN values were identified as failure modes needing necessary corrective action, respectively. Team 1 and Team 2 identified five and six failure modes needing urgent corrective action respectively, with two being commonly identified. Of the failure modes needing necessary corrective actions, about a third were commonly identified by both teams. These results show inconsistency in the outcome of the FMEA. To improve consistency, we recommend that FMEA is always carried out under the supervision of an experienced FMEA-facilitator and that the FMEA team has at least two members with competence in the analytical method to be validated. However, the FMEAs of both teams contained valuable information that was not identified by the other team, indicating that this inconsistency is not always a drawback.

Disintegration of sublingual tablets: proposal for a validated test method and acceptance criterion.

In the Netherlands the market share of isosorbide dinitrate 5 mg sublingual tablets is dominated by 2 products (A and B). In the last few years complaints have been received from health care professionals on product B. During patient use the disintegration of the tablet was reported to be slow and/or incomplete, and ineffectiveness was experienced. In the European Pharmacopoeia (Ph. Eur.) no requirement is present for the disintegration time of sublingual tablets. The purpose of this study was to compare the in vitro disintegration time of products A and B, and to establish a suitable test method and acceptance criterion. A and B were tested with the Ph. Eur. method described in the monograph on disintegration of tablets and capsules as well as with 3 modified tests using the same Ph. Eur. apparatus, but without movement of the basket-rack assembly. In modified test 1 and modified test 2 water was used as medium (900 ml and 50 ml respectively), whereas in modified test 3 artificial saliva was used (50 ml). In addition, disintegration was tested in Nessler tubes with 0.5 and 2 ml of water. Finally, the Ph. Eur. method was also applied to other sublingual tablets with other drug substances on the Dutch market. With modified test 3 no disintegration could be achieved within 20 min. With the Ph. Eur. method and modified tests 1 and 2 product A and B differed significantly (p < 0. 001), with product B having longer disintegration times. These 3 methods were capable of discriminating between products and between batches. The time measured with the Ph. Eur. method was significantly lower compared to modified tests 1 and 2 (p < 0.001) and correlated well with the Nessler tube results. It is concluded that the in vivo complaints on product B could be related to the in vitro data. Furthermore, it is proposed that for immediate release of sublingual tablets the disintegration time should be tested. The Ph. Eur. method is considered suitable for this test. In view of the products currently on the market and taking into consideration requirements in the United States Pharmacopeia and Japanese Pharmacopoeia, an acceptance criterion of not more than 2 min is proposed.

An investigation into the predictive value of cascade impactor results for side effects of inhaled salbutamol.

The aim of this study was to compare the Multistage Liquid Impinger (MSLI) and the Andersen Cascade Impactor (ACI) with respect to their power to predict differences in side effects of salbutamol delivered by a dry powder inhaler. Three preparations with the same nominal dose and the same inhaler device but generating aerosols with different aerodynamic particle size distributions were administered to six healthy volunteers in a randomized, placebo-controlled, four-way crossover study. Cumulative doses from 400 up to 1600 microg were given. The serum potassium level (K+-serum) and the heart rate (HR) were measured at baseline and 15 min after each dose. Both the MSLI and ACI showed large differences between the aerodynamic particle size distributions of the three preparations. The decrease in K+-serum revealed significant differences between the three active preparations and was significant for doses of 800 microg and higher. The HR results showed differences between the active preparations only at a nominal dose of 1600 microg and only for the preparation with the highest fine particle dose (FPD) compared to the other two preparations. The K+-serum appears to be a more sensitive measure for side effects than the HR. In vivo-in vitro correlations (IVIVCs) were established between the amounts of salbutamol deposited on the various cumulative impactor stages and the K+-serum. The best IVIVCs were obtained in the FPD range, resulting in correlation coefficients of at least 0.78. It is concluded that cascade impactor results in the FPD range of the MSLI as well as the ACI correlate well with the K+-serum. Cascade impactor analysis thus provides a clinically meaningful tool in the development and the quality control of salbutamol inhalation powders.

Drug output of unvented jet nebulizers as a function of time.

Nebulizer drug output rate increases during the nebulization. For unvented jet nebulizers, a physical and mathematical model based on the efficiency of the nebulization process is presented for this phenomenon. Formulas are derived for the cumulative drug output and the drug output rate of the nebulization process. The model is compared with the model proposed by Coates et al. [J. Aerosol. Med. 11 (1998) 101]. Both models are supported by experimental literature data. Both models predict the experimental values well but the proposed model allows more easy prediction of the influence of small changes in the nebulization conditions and the calculation of the cumulative drug output for a related process. From literature data it is shown that the efficiency of an unvented jet nebulization process of diluted aqueous solutions is relatively insensitive to small changes in the concentration as well as to small changes in aspiration flow but is sensitive to the humidity of the compressor gas only.

Equivalence testing of salbutamol dry powder inhalers: in vitro impaction results versus in vivo efficacy.

The aim of the study was to evaluate several impactors for in vitro equivalence testing of salbutamol with respect to efficacy and to define in vitro equivalence limits validated with in vivo efficacy data. The four impactors described in Supplement 2000 of the European Pharmacopoeia were used: Glass Impinger (GI), Metal Impinger (MI), Multistage Liquid Impinger (MSLI) and Andersen Cascade Impactor (ACI). Three salbutamol dry powder formulations with different fine particle doses (FPDs) were prepared and the aerodynamic particle size distribution was measured. For each impactor also the recovery was determined. The same three preparations were administered to 12 asthmatic patients in a randomized, placebo-controlled, four-way crossover study. Cumulative doses from 50 microg up to 400 microg were given. The FEV(1) was measured at baseline and 15 min after each dose. The in vitro results showed large differences between the FPDs of the three preparations with all impactors, whereas only small differences were observed between the four impactors. Since the recoveries of the MI and GI were low, in vitro equivalence testing should only be performed with the MSLI or ACI. The in vivo measurements did not show significant differences in efficacy between the three active preparations, even at the most discriminatory dose of 50 microg. It is concluded that in case there are no relevant differences between delivered dose, inhalation device and excipients, for salbutamol dry powder inhalers equivalence can be assumed when the 90% confidence interval for the FPD ratio of the test product and reference product is within 0.50-1.20 and each of the two products has a FPD (particles <6 microm) of at least 10 microg.

Metal versus plastic spacers: an in vitro and in vivo comparison.

This study compared the metal Nebuchamber with the polycarbonate Volumatic spacer in vivo as well as in vitro. Seventeen asthmatic patients were evaluated in a crossover placebo-controlled double-blind study. Bronchodilation, heart rate and serum potassium levels were measured at baseline and 15 min after administration of salbutamol. Cumulative dose-response curves (200, 400, 800 and 1600 microg) were constructed. The Andersen Cascade Impactor was used to compare the aerodynamic particle size distribution. The FEV(1) measurements showed highly significant differences between placebo and the two active preparations (P<0.001), but not between the two active preparations (P=0.433). The serum potassium levels also showed highly significant differences between placebo and the two active preparations (P=0.009), but not between the two active preparations (P=0.532). Only 1600 microg salbutamol dose raised the heart rate significantly, but the difference between the two active preparations was not significant. The in vitro deposition study revealed no significant differences in the delivered dose or in the fine particle dose (P>0.05). In conclusion, there are no significant differences between the Volumatic and Nebuchamber either in vivo or in vitro.

Equivalence testing and equivalence limits of metered-dose inhalers and dry powder inhalers measured by in vitro impaction.

In this study, criteria for the acceptability of comparative in vitro equivalence testing are proposed. Furthermore, the following equivalence limits for in vitro impaction methods are postulated: the 90% confidence interval (CI) of the in vitro deposition ratio of the test product and the reference product should lie within 0.80-1.20. The aim of this study was to challenge these limits by applying them to in vitro impaction results of several groups of pressurized metered-dose inhalers and dry powder inhalers containing salbutamol and beclomethasone dipropionate. The deposition results were obtained with the Twin Impinger. All products had a marketing authorization in The Netherlands and were considered therapeutically equivalent within each group. The postulated equivalence limits/group were challenged by fictitiously assigning a preparation as a test product or reference product and calculating the 90% CI of the deposition ratio of the test and reference products. All possible combinations of products within a group were tested. The products were considered equivalent if the 90% CI of the quotient lay within 0.80-1.20. In most cases, the quotient of the test product and reference product remains within 0.80-1.20, but due to a high variability in the deposition results of several products, the 90% CI of the quotient sometimes falls outside the proposed equivalence limits. It is concluded that the equivalence limits postulated are rather conservative, with respect to accepting equivalence. The limits can therefore serve as a prudent predictor of equivalence within the acceptability criteria proposed, but have to be further validated.