ESBL infection incidence increases especially in elderly population (Observatoire National de l'Epidémiologie de la Résistance Bactérienne aux Antibiotiques (ONERBA) www.onerba.org). SC antibiotic route is sometimes the only option available for infected elderly patients (delirium, dementia or no venous access) and presents advantages like greater patient comfort, less nursing time and decrease hospital duration. Ertapenem has a relatively long half life (4 hours) compared to imipenem (1 hour) and a less broad spectrum. Two studies compared the ertapenem pharmacokinetics regarding IV or SC administration. The first concerned 6 patients admitted in ICU and the second 16 patients in internal medicine department. They found IV and SC administrations were equivalent considering that ertapenem antimicrobial activity was time dependent. In fact, a reduction of peak concentration and of time to peak concentration was observed in both studies, but the Area Under the Curve were similar especially the time spent over the Minimal Inhibitory Concentration. Both studies did not observe any severe adverse effects. Because of these promising results and despite not being approved yet, SC Ertapenem, is commonly used in geriatric department. This administration route is chosen when no other option is available, for instance in cases of behavioural disturbance and lack of venous access.