Determination of bioequivalence for drugs with narrow therapeutic index

The US Food and Drug Administration (FDA) has recently suggested that the bioequivalence (BE) for products of drugs with narrow therapeutic indices (NTI) be assessed by the approach of reference-scaled average BE (SABE). Subsequently, in December, 2012, the FDA issued draft guidances for the comparison of products of warfarin sodium and of tacrolimus. The guidances expect that 4-period studies be performed, that the results be evaluated by SABE, and that the analysis include also unscaled average BE as well as the comparison of the estimated within-subject variations (sW) of the test and reference drug products. This communication discusses the new guidances and suggests considerations to reduce the regulatory burden. It is demonstrated that SABE could be applied when the within-subject variation of the reference product is not higher than 21.42%. Beyond this variation, the BE limits would remain 80% to 125%, as usual. No further testing by unscaled average BE is needed. It is also suggested that a comparison of the within-subject variations of the two drug products although interesting for both NTI and other drugs, is not essential for the determination of BE. In addition, when the within-subject variabilities are low then their ratio depends mainly on the non-product dependent factors. Moreover, introduction of an additional test would affect the probabilities involved in the primary comparison of the two means. Therefore, the test of comparing variances is not needed and replicate measurements of the test formulation need not be performed. Alternative considerations and approaches, including the use of partial AUC's, are suggested for the determination of BE for NTI drugs.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

Bioequivalence metrics for absorption rates: linearity, specificity, sensitivity

Aims: In order to ensure the therapeutic equivalence of generic products, it would be important to contrast measures additional to Cmax in order to assess differences in absorption rates. Our aim was to compare partial AUC (PAUC), Swing, and PTF to Cmax in terms of sensitivity, specificity and linearity under identical kinetic conditions. Methods: Single-dose and multiple-dose concentration curves were generated assuming one-compartment models. Kinetic sensitivity curves were obtained by gradually changing the absorption rate constant and keeping all other parameters fixed. Results: Ideally, a metric should reflect specifically the investigated kinetic feature (e.g., the rate of absorption), be linearly related to it, and should exhibit high kinetic sensitivity. Cmax is related nonlinearly to the rate of absorption, is nonspecific to it (reflects also the extent of absorption as well as the rates of disposition processes), lacks kinetic sensitivity even following a single administration. Compared to Cmax, PAUC was always more sensitive under every investigated condition. Swing and PTF showed high kinetic sensitivity but, in contrast to PAUC, they could be evaluated only in multiple-dose studies. Conclusion: Under identical conditions, different metrics provide widely differing point estimates. Differences in kinetic sensitivity among bioequivalence metrics should be accounted for when results of different metrics are compared

A kis „n”, nagy „P” probléma a neuropszichofarmakológiában, avagy hogyan kontrolláljuk a hamis felfedezések arányát

Számos korszerű neuropszichofarmakológiai vizsgálati módszer jellegzetessége, hogy aránylag kevés vizsgálati egyénről (n) nagyon sok adatot (paramétert, P) gyűjt. Példaképpen említhetjük a képalkotó módszereket (pl. funkcionális mágneses rezonancia és egyéb képalkotó eljárásokat), az elektroenkefalográfiát (EEG), vagy a genomikai vizsgálatokat. Egyetlen microarray chip például több ezer próbát tartalmazhat, azaz a P ezres nagyságrendekkel haladhatja meg az n-t. Az ilyen elrendezésű vizsgálatok elemzése komoly statisztikai problémákat vet fel, amit a statisztikai szakirodalomban kis "n" nagy "P" problémának neveznek. A többszörös tesztelés problémája akkor lép fel, ha két vagy több csoportba tartozó egyéneket hasonlítunk össze a mért P számú jellemző alapján. Amennyiben az összehasonlítás az egyes jellemzők alapján történik, akkor akár több ezer statisztikai hipotézisvizsgálat elvégzése is szükségessé válhat. Amennyiben a többszörös tesztelés okozta megnövekedett klasszifikációs hibát nem vesszük figyelembe, akkor számos statisztikailag szignifikáns különbséget fedezhetünk fel a vizsgálati csoportok között. Azonban ezeknek a felfedezéseknek egy része valójában a véletlen műve és ezek a kísérleti eredmények általában nem reprodukálhatóak. A problémára több megoldás is született. Ezek közül cikkünkben a klaszter szintű összehasonlítást, valamint a hamis találati arányon alapuló statisztikai tesztet mutatjuk be

Additive effect of 5-HT2C and CB1 receptor blockade on the regulation of sleep-wake cycle

BACKGROUND:Previous data show that serotonin 2C (5-HT2C) and cannabinoid 1 (CB1) receptors have a role in the modulation of sleep-wake cycle. Namely, antagonists on these receptors promoted wakefulness and inhibited rapid eye movement sleep (REMS) in rodents. The interaction of these receptors are also present in other physiological functions, such as the regulation of appetite. Blockade of 5-HT2C receptors modulat the effect of CB1 receptor antagonist, presumably in consecutive or interdependent steps. Here we investigate, whether previous blockade of 5-HT2C receptors can affect CB1 receptor functions in the sleep-wake regulation. RESULTS:Wistar rats were equipped with electroencephalography (EEG) and electromyography (EMG) electrodes. Following the recovery and habituation after surgery, animals were injected intraperitoneally (ip.) with SB-242084, a 5-HT2C receptor antagonist (1.0 mg/kg) at light onset (beginning of passive phase) followed by an injection with AM-251, a CB1 receptor antagonist (5.0 or 10.0 mg/kg, ip.) 10 min later. EEG, EMG and motor activity were analyzed for the subsequent 2 h. Both SB-242084 and AM-251 increased the time spent in active wakefulness, while decreased the time spent in non-REMS and REMS stages in the first 2 h of passive phase. In combination, the effect of the agents were additive, furthermore, statistical analysis did not show any interaction between the effects of these drugs in the modulation of vigilance stages. CONCLUSIONS:Our results suggest that 5-HT2C receptor blockade followed by blockade of CB1 receptors evoked additive effect on the regulation of sleep-wake pattern

Neuro- és citoprotektív mechanizmusok kutatása. = Studies on neuro- and cytoprotective mechanisms.

Az elmúlt négy évtized magyar gyógyszerkutatásának sikervegyületét, a (-)-deprenylt tanulmányoztuk a neuroprotektív hatás újabb lehetőségeinek feltárására. Vizsgáltuk a deprenyl-N-oxid képződését és farmakokinetikáját. Megállapítottuk, hogy a propargyl-csoporttal rendelkező deprenyl metabolit, a deprenyl-N-oxid nagy koncentrációban sem idéz elő apoptózist, ugyanakkor a belőle kis mennyiségben visszaalakuló deprenyl hatékonyan kivédheti az apoptotikus sejtpusztulást. A neurodegeneratív betegségek gyógykezelésére használt deprenylt p.o. adják 5-10 mg dózisban, melynek 75 %-a "first-pass" metabolizmust szenved. A szokványos dózisban parenterálisan adott (-)-deprenyl elkerülve a "first-pass" metabolizmust bénítja a MAO-A-t is és alkalmas antidepresszív hatás kiváltására. Ebből a szempontból a transzdermális vagy liposzóma készítmény tűnik előnyösebbnek. Az SSAO fiziológiai és pathofiziológiai szerepének megismerését hátráltatja egy szelektív, hatékony és emberi terápiában alkalmazható gátlószer hiánya. Duellinnel kezelt parkinsonos betegeken követtük az SSAO enzim aktivitását. A Duellin carbidopa komponense olyan tartós SSAO-gátolt állapotot hoz létre, mely alkalmas lehet különböző kórképekben az ok-okozat elemzésére. Kapilláris elektroforézis módszert dolgoztunk ki az oxidatív károsodást előidéző reaktív gyökök stabil végtermékeinek meghatározására. A módszer lehetővé teszi új targetek vizsgálatát, melyek szerepe fontosnak tűnik a neuroprotekció kialakulásában. | (-)-Deprenyl, the success compound of the Hungarian drug research in the last four decades, has been studied to reveal new ways of neuroprotection. Metabolic formation and pharmacokinetics of deprenyl-N-oxide have been clarified. This propargyl derivative does not induce apoptosis even at a high concentration, however its small portion is converted back to deprenyl, low concentration of which may prevent apoptotic cell death. Daily 5-10 mg oral deprenyl is used in neurodegenerative diseases, although 75% of the dose undergoes first pass metabolism, and only 25% reaches the systemic circulation. Similar dose of deprenyl given parenterally provides the inhibition of both monoamine oxidase A and B (because of its much less first pass metabolism), resulting in antidepressant effect. Transdermal or liposome formulations seem to be preferred. The lack of effective, selective SSAO inhibitor makes the elucidation of the physiological and pathophysiological role of the enzyme difficult. Serum SSAO activity in parkinsonian patients treated with Duellin was measured. As the hydrazine derivative carbidopa in Duellin provided long-term inhibition of SSAO, it could be used in further studies to clarify SSAO function. Capillary electrophoresis methods have been developed to measure the stable end-products of the cytotoxic reactive oxygen and nitrogen species. These methods allow the study of new targets in neuroprotection

Hidden Cardiotoxicity of Rofecoxib Can be Revealed in Experimental Models of Ischemia/Reperfusion

Cardiac adverse effects are among the leading causes of the discontinuation of clinical trials and the withdrawal of drugs from the market. The novel concept of 'hidden cardiotoxicity' is defined as cardiotoxicity of a drug that manifests in the diseased (e.g. ischemic/reperfused), but not in the healthy heart or as a drug-induced deterioration of cardiac stress adaptation (e.g. ischemic conditioning). Here, we aimed to test if the cardiotoxicity of a selective COX-2 inhibitor rofecoxib that was revealed during its clinical use, i.e., increased occurrence of proarrhythmic and thrombotic events, could have been revealed in early phases of drug development by using preclinical models of ischemia/reperfusion (I/R) injury. Rats that were treated with rofecoxib or vehicle for four weeks were subjected to 30 min. coronary artery occlusion and 120 min. reperfusion with or without cardioprotection that is induced by ischemic preconditioning (IPC). Rofecoxib increased overall the arrhythmias including ventricular fibrillation (VF) during I/R. The proarrhythmic effect of rofecoxib during I/R was not observed in the IPC group. Rofecoxib prolonged the action potential duration (APD) in isolated papillary muscles, which was not seen in the simulated IPC group. Interestingly, while showing hidden cardiotoxicity manifested as a proarrhythmic effect during I/R, rofecoxib decreased the infarct size and increased the survival of adult rat cardiac myocytes that were subjected to simulated I/R injury. This is the first demonstration that rofecoxib increased acute mortality due to its proarrhythmic effect via increased APD during I/R. Rofecoxib did not interfere with the cardiprotective effect of IPC; moreover, IPC was able to protect against rofecoxib-induced hidden cardiotoxicity. These results show that cardiac safety testing with simple preclinical models of I/R injury uncovers hidden cardiotoxicity of rofecoxib and might reveal the hidden cardiotoxicity of other drugs

Acute escitalopram treatment inhibits REM sleep rebound and activation of MCH-expressing neurons in the lateral hypothalamus after long term selective REM sleep deprivation.

RATIONALE: Selective rapid eye movement sleep (REMS) deprivation using the platform-on-water ("flower pot") method causes sleep rebound with increased REMS, decreased REMS latency, and activation of the melanin-concentrating hormone (MCH) expressing neurons in the hypothalamus. MCH is implicated in the pathomechanism of depression regarding its influence on mood, feeding behavior, and REMS. OBJECTIVES: We investigated the effects of the most selective serotonin reuptake inhibitor escitalopram on sleep rebound following REMS deprivation and, in parallel, on the activation of MCH-containing neurons. METHODS: Escitalopram or vehicle (10 mg/kg, intraperitoneally) was administered to REMS-deprived (72 h) or home cage male Wistar rats. During the 3-h-long "rebound sleep", electroencephalography was recorded, followed by an MCH/Fos double immunohistochemistry. RESULTS: During REMS rebound, the time spent in REMS and the number of MCH/Fos double-labeled neurons in the lateral hypothalamus increased markedly, and REMS latency showed a significant decrease. All these effects of REMS deprivation were significantly attenuated by escitalopram treatment. Besides the REMS-suppressing effects, escitalopram caused an increase in amount of and decrease in latency of slow wave sleep during the rebound. CONCLUSIONS: These results show that despite the high REMS pressure caused by REMS deprivation procedure, escitalopram has the ability to suppress REMS rebound, as well as to diminish the activation of MCH-containing neurons, in parallel. Escitalopram caused a shift from REMS to slow wave sleep during the rebound. Furthermore, these data point to the potential connection between the serotonergic system and MCH in sleep regulation, which can be relevant in depression and in other mood disorders