Imipenem is crystalline soid and its stable for 24 month at 3-8 degree centigrade.Its packeging should be under nitrogen environment. In absence of nitrogen, it degraded fast. So keep under ntrogen/under vaccumised pack.

Thank Dr Rai for your kind information. But the commercially prepared imipenem antibiotic disk and Etest strips were stable for longer duration without nitrogen environment? how could it be possible?

Lyophilize your disks within 1 h of preparation.