Concentration-Response Relationship of Hearing Impairment Caused by Quinine and Salicylate: Pharmacological Similarities but Different Molecular Mechanisms.

This review has the purpose to summarize concentration-effect studies made with quinine and to compare the effects on hearing between quinine and salicylate. Quinine and salicylate have roles in experimental hearing research and may induce pronounced and reversible hearing impairment when administered in sizeable doses. The quinine-induced increase in hearing threshold and its recovery can be analysed according to 'the psychophysical power function'. The power function is a special case of the Hill equation when the stimulus (e.g. a drug concentration) is exceedingly small compared with the concentration that would elicit a half-maximum response. Quinine and salicylate induce sensorineural hearing impairment and tinnitus when given in higher dose ranges in man. The drugs influence the presence, magnitude, and quality of audiological responses, such as spontaneous and evoked otoacoustic emissions. Quinine reversibly reduces frequency selectivity and hearing sensitivity, whereas the self-attained most comfortable speech level and the acoustic stapedius reflex are not affected, that is the dynamic range of hearing is reversibly reduced. This observation supports the view that quinine acts on the outer hair cell of the cochlea. Both drugs share a protective effect against the permanent hearing damages caused by gentamicin. This action is interpreted as a request for functioning mechanoelectric transducer (MET) channels to elicit the ill effect of aminoglycosides. Both drugs may interfere with the cochlear amplifier through blocking MET channels and the motor protein prestin. This review finds considerable overlap between type and extent of pharmacological actions of quinine and salicylate, supposedly caused by partly shared mechanisms of action but performed with different molecular mechanisms.

The continuing challenge of providing drug information services to diminish the knowledge--practice gap in medical practice.

Information must be collected, evaluated and utilized to support every qualified activity. Medicine, with a written scientific tradition stretching back more than 2,000 years, is no exception. Here, we discuss a number of important items associated with the establishment of a drug information centre run by clinical pharmacologists and information pharmacists, serving a broad demand, mainly among clinical specialists. The working methods include a professional literature search, critical evaluation of the material, writing a structured answer, quality control, feedback to the inquirer and storage in a database which is publicly available. One can foresee even more complex systems wherein a number of active and specialized databases communicate to provide relevant advice and support at the point of care, supplying information on drug recommendations, reimbursement, environmental aspects, antimicrobial resistance, pharmacogenetics and adverse effects, and linked to a list of prescribed drugs for the individual patient. This will be possible in both rich and poor countries through the application of modern and developing information technology. However, research on the best and safest methods of such decision support systems will be needed to ensure that they really do improve the quality of drug prescribing and use.

The global need for effective antibiotics-a summary of plenary presentations.

To highlight the global need for effective antibiotics and explore possible concerted actions for change, cross-cutting plenary sessions served to frame the program of the conference. These sessions contained presentations on the present state of antibacterial resistance and the availability, the use and misuse of antibiotics. A number of possible actions were discussed, such as rational use of and access to antibiotics from various perspectives. The roles of vaccines and diagnostics were touched upon and followed by in depth discussions on supply-side bottlenecks with their scientific, regulatory and financial challenges. The value chain for research and development (R&D) of antibiotics has to be reengineered if we are to realize the development of much needed new antibiotics. This challenge will require a multitude of actions, some of which are related to changing the financial realities of antibiotics and interventions by global and regional institutions.

Muscle toxicity with statins.

PURPOSE: Statins rarely cause serious muscle toxicity and rhabdomyolysis. The aim of our investigation was to identify and quantify potential risk factors for statin-induced rhabdomyolysis. METHODS: All cases of suspected adverse reactions to statins reported to the Swedish Adverse Drug Reactions Advisory Committee until 15 September 2006 containing the codes myalgia, myopathy, increased serum creatine kinase (CK), myoglobinuria or rhabdomyolysis were included in the study. Cases were classified into different CK categories, where cases with CK levels >10 times the upper limit of normal (ULN) laboratory range were compared with cases with normal CK levels (in some analyses cases with CK not measured were also included as controls). Fisher's test and multiple logistic regression were used to test the degree of association. RESULTS: A total of 338 cases with muscle toxicity were identified. CK had not been measured in 148 cases. Of the remaining 190 cases, 59 were classified as rhabdomyolysis, 62 had CK increases below the level of rhabdomyolysis, 69 had normal CK and 2 contained insufficient information to classify the degree of CK increase. A high statin dose and concomitant interacting drug treatment were over-represented among cases with rhabdomyolysis compared with cases with normal CK. Renal disease and unusual strenuous muscular activity were also associated with an increased risk of rhabdomyolysis when the control group included cases with CK not measured. CONCLUSION: Results from our study support previous studies indicating that the risk of rhabdomyolysis with statin treatment increases with increase in systemic exposure to the statin. Renal disease and unusual strenuous muscular activity may also contribute to an increased risk of rhabdomyolysis.

Interindividual variability in the concentration-effect relationship of antilymphocyte globulins - a possible influence of FcgammaRIIIa genetic polymorphism.

AIMS: Polyclonal antilymphocyte globulins (ALGs) are currently used in transplantation, but the sources of interindividual variability of their effect are poorly understood. No pharmacokinetic-pharmacodynamic (PK-PD) study of ALG is available. Moreover, the genetic polymorphism of FcgammaRIIIa, a receptor for the Fc portion of immunoglobulins involved in antibody-dependent cellular cytotoxicity (ADCC), may influence their concentration-effect relationship. METHODS: Fourteen kidney transplant patients treated by horse ALG were included in a prospective, noncomparative study. A population two-compartment PK model including a time dependence of the central volume of distribution was developed. Total lymphocyte count was used as biomarker of effect. Concentration-effect data were described using a physiological indirect response model, combining concentration-dependent and -independent inhibitions of lymphocyte input into the circulation. In addition, six kidney transplant patients in whom ALG concentrations were not available were included retrospectively. All patients were genotyped for FCGR3A. RESULTS: Both the PK and the PK-PD model described the data satisfactorily and showed high interindividual variability. Asymptotic T(1/2)-alpha and T(1/2)-beta-values were 1.3 and 25 days, respectively. The concentration of ALG leading to a 50% inhibition of lymphocyte input (IC(50)) was lower in FCGR3A-V carriers than in FCGR3A-F/F patients (383 +/- 199 vs. 593 +/- 209 mg l(-1), P = 0.008). CONCLUSIONS: This is the first description of the ALG effect on lymphocyte count using PK-PD modelling. Our results show that part of the variability in their concentration-effect relationship may be explained by FcgammaRIIIa genetic polymorphism and therefore that horse ALG may deplete lymphocytes by ADCC.

The conscientious judgement of a DSMB--statistical stopping rules re-examined.

OBJECTIVE: In the light of the recent failure of a large cardiovascular mortality and morbidity study with torcetrapib, we have undertaken a post hoc review of the decisions taken by the Data and Safety Monitoring Board (DSMB) in that study. A number of other studies in which complex decisions were made by DSMBs are also reviewed. RESULTS: The examples illustrate the complexities involved in the decision-making process by DSMBs and indicate that too much reliance on formal statistical stopping rules should be avoided due to a risk of delaying the identification of an unacceptable emergent safety signal. METHODS: The review was based on information submitted by the sponsors of the studies to the Medical Products Agency. CONCLUSIONS: Multiple approaches to assessing the efficacy and safety in clinical trials need to be considered in order to facilitate early stopping of clinical trials with a negative risk benefit balance. Such systems may, for example, include the use of p-value flags and/or a complementary statistical analysis of the likelihood of achieving the study objective based on the data obtained to date.

The effect of intravenously administered mexiletine on tinnitus - a pilot study.

The effect of intravenously administered mexiletine on subjective tinnitus and hearing was studied in six patients, who initially responded positively to lidocaine. Distinct mexiletine-induced decreases in tinnitus loudness were demonstrated in three subjects, as reflected by maximum VAS (visual analogue scale) level reduction of 34%, 95%, and 100%, respectively. One subject reported change in tinnitus pitch, another one showed a slight (18% on VAS) tinnitus reduction, and one subject disclosed no effect. Side effects were seen only during one of seven infusions. Mexiletine induced shifts in pure-tone threshold, transient evoked otoacoustic emission, and acoustic reflex threshold, probably reflecting a reversible interference in the function of organ of Corti. The concentration effect relationship remained unclear and no general 'therapeutic' level could be identified. This study confirms the effect of mexiletine on the auditory function and its potential as a possible therapeutic agent or a model for further development in tinnitus pharmacotherapy.

Are pharmaceuticals potent environmental pollutants? Part I: environmental risk assessments of selected active pharmaceutical ingredients.

As part of achieving national environmental goals, the Swedish Government commissioned an official report from the Swedish Medical Products Agency on environmental effects of pharmaceuticals. Considering half-lives/biodegradability, environmental occurrence, and Swedish sales statistics, 27 active pharmaceutical ingredients were selected for environmental hazard and risk assessments. Although there were large data gaps for many of the compounds, nine ingredients were identified as dangerous for the aquatic environment. Only the sex hormones oestradiol and ethinyloestradiol were considered to be associated with possible aquatic environmental risks. We conclude that risk for acute toxic effects in the environment with the current use of active pharmaceutical ingredients is unlikely. Chronic environmental toxic effects, however, cannot be excluded due to lack of chronic ecotoxicity data. Measures to reduce potential environmental impact posed by pharmaceutical products must be based on knowledge on chronic ecotoxic effects of both active pharmaceutical ingredients as well as excipients. We believe that the impact pharmaceuticals have on the environment should be further studied and be given greater attention such that informed assessments of hazards as well as risks can be done.

Are pharmaceuticals potent environmental pollutants? Part II: environmental risk assessments of selected pharmaceutical excipients.

As part of achieving national environmental goals, the Swedish Government commissioned a report from the Swedish Medical Products Agency on environmental effects of pharmaceuticals and cosmetics and hygiene products. Five excipients used in pharmaceutical products were selected for environmental risk assessments, applying the computer-based model EUSES. Docusate sodium was identified as a possible risk for sediment-dwelling organisms when taking the total amount used into account. Although, experimental toxicity data on sediment-dwelling organism and data on concentrations in sediments are still required before firm conclusions regarding the environmental risk can be made. The environmental risks posed by excipients used in pharmaceutical products are likely to be negligible. This study identifies that knowledge gaps regarding environmental risks posed by pharmaceutical excipients are evident.

Mechanism-based pharmacokinetic-pharmacodynamic modeling-a new classification of biomarkers.

In recent years, pharmacokinetic/pharmacodynamic (PK/PD) modeling has developed from an empirical descriptive discipline into a mechanistic science that can be applied at all stages of drug development. Mechanism-based PK/PD models differ from empirical descriptive models in that they contain specific expressions to characterize processes on the causal path between drug administration and effect. Mechanism-based PK/PD models have much improved properties for extrapolation and prediction. As such, they constitute a scientific basis for rational drug discovery and development. In this report, a novel classification of biomarkers is proposed. Within the context of mechanism-based PK/PD modeling, a biomarker is defined as a measure that characterizes, in a strictly quantitative manner, a process, which is on the causal path between drug administration and effect. The new classification system distinguishes seven types of biomarkers: type 0, genotype/phenotype determining drug response; type 1, concentration of drug or drug metabolite; type 2, molecular target occupancy; type 3, molecular target activation; type 4, physiological measures; type 5, pathophysiological measures; and type 6, clinical ratings. In this paper, the use of the new biomarker classification is discussed in the context of the application of mechanism-based PK/PD analysis in drug discovery and development.

The effect of ketoconazole and diltiazem on oestrogen metabolism in postmenopausal women after single dose oestradiol treatment.

AIMS: The effect of the CYP3A4 inhibitors ketoconazole and diltiazem on the pharmacokinetics of oestrone was studied in six healthy postmenopausal women after treatment with a single oral dose of oestradiol. METHODS: Plasma oestrone concentrations were measured following the administration of 1) oestradiol, 2) oestradiol and ketoconazole and 3) oestradiol and diltiazem. RESULTS: Treatment with ketoconazole increased the AUC of oestrone (+ 4029 nmol l-1 h; 95% CI on the difference: 1588, 6471) and its Cmax (+ 306 nmol l-1; 95% CI on the difference: 117, 496). The AUC and Cmax of oestrone tended to increase on treatment with diltiazem although this did not reach the level of statistical significance. CONCLUSIONS: The small increase in the plasma concentrations of oestrone formed from 17beta-oestradiol during co-administration with ketoconazole is unlikely to be clinically significant.