Significant impact of time-of-day variation on metformin pharmacokinetics.

AIMS/HYPOTHESIS: The objective was to investigate if metformin pharmacokinetics is modulated by time-of-day in humans using empirical and mechanistic pharmacokinetic modelling techniques on a large clinical dataset. This study also aimed to generate and test hypotheses on the underlying mechanisms, including evidence for chronotype-dependent interindividual differences in metformin plasma and efficacy-related tissue concentrations. METHODS: A large clinical dataset consisting of individual metformin plasma and urine measurements was analysed using a newly developed empirical pharmacokinetic model. Causes of daily variation of metformin pharmacokinetics and interindividual variability were further investigated by a literature-informed mechanistic modelling analysis. RESULTS: A significant effect of time-of-day on metformin pharmacokinetics was found. Daily rhythms of gastrointestinal, hepatic and renal processes are described in the literature, possibly affecting drug pharmacokinetics. Observed metformin plasma levels were best described by a combination of a rhythm in GFR, renal plasma flow (RPF) and organic cation transporter (OCT) 2 activity. Furthermore, the large interindividual differences in measured metformin concentrations were best explained by individual chronotypes affecting metformin clearance, with impact on plasma and tissue concentrations that may have implications for metformin efficacy. CONCLUSIONS/INTERPRETATION: Metformin's pharmacology significantly depends on time-of-day in humans, determined with the help of empirical and mechanistic pharmacokinetic modelling, and rhythmic GFR, RPF and OCT2 were found to govern intraday variation. Interindividual variation was found to be partly dependent on individual chronotype, suggesting diurnal preference as an interesting, but so-far underappreciated, topic with regard to future personalised chronomodulated therapy in people with type 2 diabetes.

Associations Between Abstract Concepts: Investigating the Relationship Between Deictic Time and Valence.

The present study examines whether deictic time and valence are mentally associated, with a link between future and positive valence and a link between past and negative valence. We employed a novel paradigm, the two-choice-sentence-completion paradigm, to address this issue. Participants were presented with an initial sentence fragment that referred to an event that was either located in time (future or past) or of different valence (positive or negative). Participants chose between two completion phrases. When the given dimension in the initial fragment was time, the two completion phrase alternatives differed in valence (positive vs. negative). However, when the given dimension in the initial fragment was valence, the two completion phrase alternatives differed in time (future vs. past). As expected, participants chose completion phrases consistent with the proposed association between time and valence. Additional analyses involving individual differences concerning optimism/pessimism revealed that this association is particularly pronounced for people with an optimistic attitude.

Alternative Treatment Regimens With the PCSK9 Inhibitors Alirocumab and Evolocumab: A Pharmacokinetic and Pharmacodynamic Modeling Approach.

Alirocumab and evolocumab are 2 human monoclonal antibodies that inhibit the proprotein convertase subtilisin/kexin type 9 (PCSK9). These antibodies can potently lower low-density lipoprotein cholesterol (LDLc) serum concentrations. The aims of this analysis were to develop a pharmacokinetic (PK) and pharmacodynamic (PD) model for both antibodies, to simulate and investigate different dosage and application regimens, and finally, to note the effects on LDLc levels. Alirocumab was clinically studied and approved with 2 doses, 75 and 150 mg every 2 weeks (Q2W), whereas evolocumab was tested and approved with 2 dosing intervals, 140 mg Q2W and 420 mg Q4W. Data were digitized from published studies describing alirocumab and evolocumab PK, as well as LDLc levels in humans for various single and multiple doses. Alirocumab dosages ranged between 75 and 300 mg and evolocumab from 7 to 420 mg. The analysis was performed using a nonlinear mixed-effects modeling technique. A 2-compartment model with first-order absorption and saturable elimination described the PK of both antibodies best. LDLc levels were described by a turnover model with zero-order synthesis rate decreased by the antibodies and a first-order degradation rate that was increased by the antibodies. Simulations show a comparable effectiveness for alirocumab 75 mg Q2W and 150 mg Q3W as well as evolucmab 140 mg Q2W and 420 mg Q5W, respectively. This is the first PK/PD model describing the link between alirocumab and evolocumab PK and LDLc concentrations. The model may serve as an important tool to simulate different dosage regimens in order to optimize therapy.