No abstract

Objective:  Lithium is a drug with a narrow therapeutic window. Concomitantly used medication is a potentially influencing factor of lithium serum concentrations. We conducted a multicentre retrospective case‐control study with the aim of investigating lithium‐related drug interactions as determinants of elevated lithium serum levels in daily clinical practice. Methods:  Cases were patients with an increase of at least 50% in lithium serum concentrations resulting in an elevated lithium serum level of at least 1.3 mmol/L, and who were not suspected of a suicide attempt. Controls were patients who showed stable lithium serum levels within the therapeutic range. Use and start of non‐steroidal anti‐inflammatory drugs, diuretics, renin–angiotensin inhibitors, theophyllin and antibiotics were investigated as potential determinants of the elevated lithium serum levels. Irregularity in lithium dispensing pattern, change in lithium dosing regimen, age, gender, prescribing physician and laboratory parameters were investigated as potential confounders. Results:  We included 51 cases and 51 controls in our study. Five (9.8%) controls and 15 (29.4%) cases used potentially interacting co‐medication [OR of 3.83 (95%CI 1.28–11.48)]. Start of potentially interacting co‐medication was observed in eight (15.7%) cases and in zero (0%) controls resulting in an OR of 20.13 (95% CI 1.13–359). After adjustment for co‐medication, irregularity in lithium dispensing pattern, change in lithium dosing regimen, and age, the statistically significant association was lost. We report an OR of 2.70 (95% CI 0.78–9.31) for use of concomitant medication, with a large contribution of antibiotic agents, and an OR of 3.14 (95% CI 1.15–8.61) for irregularity in lithium dispensing pattern. Conclusion:  Use of co‐medication, especially antibiotics, tends to be associated with elevated lithium serum levels.

A novel, pegylated, peptide-based thrombopoietin receptor agonist (peg-TPOmp) was shown to possess in vitro and in vivo thrombopoietic activity. In cell-based assays, peg-TPOmp was active at picomolar concentrations. In vivo, peg-TPOmp increased platelet production dose-dependently in rats (ED50 single i.v. dose ~ 100 μg/kg), dogs and mice. A phase I study was conducted in healthy male volunteers to investigate the tolerability, PD and PK of peg-TPOmp. Forty volunteers were randomized to receive peg-TPOmp or placebo as a single i.v. bolus injection in a ratio of 6:2. The peg-TPOmp dose range explored was 0.375, 0.75, 1.5, 2.25 or 3 μg/kg. PK analysis indicated dose-related kinetics of peg-TPOmp, although at doses of 0.75 μg/kg or lower, plasma concentrations were generally below the LOQ of 6.25 ng/mL. Mean Cmax values ranged from 11 ng/mL for 0.75 μg/kg to 62 ng/mL at 3.0 μg/kg. The mean terminal half-life ranged from approx. 18 to 36 hours. Platelet counts increased dose-dependently reaching peak levels at Day 10–12, and counts returned to baseline within 3–4 weeks. Mean peak platelet levels ranged from 315 x109/L at 0.375 μg/kg to 685 x 109/L at 3 μg/kg. Mean increase of peak platelet counts from baseline ranged from 1.4-fold at 0.375 μg/kg to 3.2-fold at 3.0 μg/kg. Endogenous TPO levels dose-dependently increased, reaching peak levels at 3 days post-dose, possibly due to a reduced rate of clearance. No significant changes were observed in blood levels of IL-6, IL-11 and EPO levels. Platelet function, assessed as collagen-induced platelet aggregation in whole blood, was not different between the treatments. None of the subjects experienced serious adverse events or dose-limiting toxicities. The most frequently observed adverse events included mild headache and fatigue and occurred both after active treatment and placebo. No antibodies against peg-TPOmp were detected. Based on the safety, PK and PD data, peg-TPOmp shows promise as an agent to treat thrombocytopenic disorders.