Rapid Desensitization with Imipenem in Penicillin Allergic Patient

Abstract

RATIONALE: Cross reactivity between penicillin and Imipenem may be as high as 47%. We modeled a rapid desensitization protocol based on a previously published report (Annals Pharmacotherapy 2003;37:513-516) of a patient allergic to penicillin who was treated with Imipenem.CASE REPORT: A 35 yo male with Tetrology of Fallot and emphysema was intubated due to respiratory failure from multilobar pneumonia with methicillin resistant Staph. epidermis. The patient had a history of diffuse rash and difficulty breathing after receiving penicillin as a child. Despite treatment with multiple alternative agents, he remained febrile and hypoxic, so he was desensitized with Imipenem.METHODS: Increasing concentrations of Imipenem were prepared in 0.9%NS. The protocol was started at 0.0001mg/ml @ 1ml/min for 30 minutes. Each of the next concentrations (0.001 mg/ml, 0.01 mg/ml, 0.1mg/ml and 1mg/ml) was initially infused @ 0.33ml/min for 30 minutes, then @ 1ml/min for 30 minutes.RESULTS: This patient tolerated desensitization well without signs of a cutaneous or systemic reaction. A serum tryptase level obtained following the desensitization was 6.9 ng/ml (nl<11.4).CONCLUSIONS: There are only three previously reported instances in the literature of penicillin allergic patients that were desensitized to imipenem. This report is another successful modified desensitization protocol. Although our patient's clinical history strongly suggests a true penicillin allergy, this was not confirmed with penicillin skin testing due to the current lack of skin testing reagents (Pre Pen™). Nevertheless, in patients with a history suspicious for penicillin allergy that require a carbapenem, this protocol may be helpful for desensitization. RATIONALE: Cross reactivity between penicillin and Imipenem may be as high as 47%. We modeled a rapid desensitization protocol based on a previously published report (Annals Pharmacotherapy 2003;37:513-516) of a patient allergic to penicillin who was treated with Imipenem. CASE REPORT: A 35 yo male with Tetrology of Fallot and emphysema was intubated due to respiratory failure from multilobar pneumonia with methicillin resistant Staph. epidermis. The patient had a history of diffuse rash and difficulty breathing after receiving penicillin as a child. Despite treatment with multiple alternative agents, he remained febrile and hypoxic, so he was desensitized with Imipenem. METHODS: Increasing concentrations of Imipenem were prepared in 0.9%NS. The protocol was started at 0.0001mg/ml @ 1ml/min for 30 minutes. Each of the next concentrations (0.001 mg/ml, 0.01 mg/ml, 0.1mg/ml and 1mg/ml) was initially infused @ 0.33ml/min for 30 minutes, then @ 1ml/min for 30 minutes. RESULTS: This patient tolerated desensitization well without signs of a cutaneous or systemic reaction. A serum tryptase level obtained following the desensitization was 6.9 ng/ml (nl<11.4). CONCLUSIONS: There are only three previously reported instances in the literature of penicillin allergic patients that were desensitized to imipenem. This report is another successful modified desensitization protocol. Although our patient's clinical history strongly suggests a true penicillin allergy, this was not confirmed with penicillin skin testing due to the current lack of skin testing reagents (Pre Pen™). Nevertheless, in patients with a history suspicious for penicillin allergy that require a carbapenem, this protocol may be helpful for desensitization.