Pharmacokinetics and Safety of Antimicrobial Agents Administered by Subcutaneous Route in Patients AGEd Over 65 Years

Antibiotic administration through subcutaneous (SC) injection is common practice in France, especially in Geriatrics as an alternative to intravenous (IV) route in case of poor venous access or delirium (Forestier et al. CMI 2015). Whereas tolerance of such a practice seems to be reasonable (Roubaud-Baudron et al. Age and Ageing 2017), sparse PK/PD data are available. Most PK/PD studies include young and healthy subjects, yet elderly patients often have multimorbidity , poly medication, renal insufficiency and cachexia which may disturb antibiotics PK/PD. Compared to intravenous (IV) route, SC route is less painful and less frequently associated with infectious or thrombotic complication. A recent study carried out in Bordeaux University Hospital comparing PK/PD data on ertapenem SC or IV administrations in patients aged over 75 showed that area under the curve (AUC) and probability to maintain free ertapenem concentration above the Minimum inhibitory concentration (MIC) during at least 40% of time (fT>MIC>40%) were not significantly different (manuscript in progress).

The investigator's hypothesis is that SC administration of amoxicillin-clavulanate, ceftriaxone and piperacillin-tazobactam has favorable pharmacokinetics and acceptable tolerance compared with IV infusion in elderly patients.

Patients receiving one of the three antibiotics by IV or SC route will be included at steady state (depending on antibiotic treatment) for several blood tests (3 or 4 depending of routes choice) and followed until 15 days after completion of antibiotic treatment in order to evaluate tolerance and efficacy of antibiotic treatment. Physicians in charge of patients will decide antibiotic prescription including administration route. The study will not influence these choices because patients will be included after antibiotic initiation.