Continuous versus intermittent infusion of temocillin, a directed spectrum penicillin for intensive care patients with nosocomial pneumonia: stability, compatibility, population pharmacokinetic studies and breakpoint selection.

BACKGROUND AND AIMS: Temocillin, a 6alpha-methoxy-penicillin stable towards most beta-lactamases (including extended-spectrum beta-lactamase), is presented as an alternative to carbapenems for susceptible Enterobacteriaceae in microbiological surveys. We aimed at documenting its potential clinical usefulness in intensive care (IC) patients using pharmacokinetic/pharmacodynamic approaches applied to conventional (twice daily) and continuous infusion (CI) modes of administration.

METHODS

(i) In vitro evaluation of temocillin stability and compatibility with other drugs under conditions pertinent of CI in IC patients; (ii) pharmacokinetic study in patients treated by CI (4 g/day; n = 6) versus [twice daily (2 g every 12 h); n = 6]; (iii) population pharmacokinetic analysis of twice daily with Monte Carlo simulations to determine 95% probability of target attainment (PTA(95)) versus MIC (based on time above MIC > or = 40% for measured free drug).

RESULTS

Temocillin was stable at 37 degrees C in 8.34% solutions for 24 h and compatible with flucloxacillin and aminoglycosides, but not with several other antibiotic and non-antibiotic drugs. With CI, stable total serum concentrations were 73.5 +/- 3.0 mg/L (SEM) and free concentration 29.3 +/- 2.8 mg/L. With twice daily, Cmax (total drug) was 147 +/- 12.3 mg/L (SEM; free drug: 50.3 +/- 15.8 mg/L), lowest trough (total drug) 12.3 mg/L, and PTA(95) (free drug) obtained for MIC < or = 8 mg/L.

CONCLUSIONS

Temocillin (4 g/day) by CI yields stable free serum concentrations above the current breakpoint (16 mg/L), although individual variations may suggest lowering the breakpoint to 8 mg/L (as for twice daily) unless the daily dose or the frequency of administration is increased.