Bioavailability and cardiovascular effects of adrenaline administered by Anapen 500 μg auto-injector in healthy volunteers.

Aims: Anaphylaxis guidelines recommend intramuscular adrenaline, commonly 300 μg administered using an auto-injector device. However, overweight/obese patients may require a higher adrenaline dose for adequate cardiovascular (CV) response. This study evaluated the pharmacokinetics (PK) and pharmacodynamic (PD) CV profiles after a single 500 μg adrenaline injection via Anapen auto-injector in healthy normal weight males and otherwise healthy, overweight or obese females.

Methods: In this exploratory open-label, single-centre study, 54 healthy volunteers aged 18-50 years received a single 500 μg adrenaline injection (Anapen auto-injector) in the thigh (antero-lateral middle third [18 males] or antero-inferior third [36 females]). Assessments included depot depth (ultrasonography), plasma adrenaline levels (liquid chromatography-tandem mass spectrometry) and heart rate (HR; ECG Holter monitor).

Results: Ultrasonography showed that 82.4% of normal weight males received intramuscular injections; all overweight and obese females received subcutaneous injections. Anapen injection produced rapid increases in circulating adrenaline levels and significant increases in systolic blood pressure (SBP) and HR. Second peak plasma adrenaline concentrations (C ) were reduced, and time to C increased in overweight and obese females compared with males with normal body mass index; area under the curve (0-240 min) (AUC ) was increased in overweight and obese females. Obese females had reduced maximal SBP values compared with normal weight males or overweight females; overweight and obese females had markedly different HR time courses compared with normal weight males.

Conclusion: A 500 μg adrenaline injection via Anapen produced rapid PK/PD changes in normal weight, overweight and obese subjects, irrespective of intramuscular or subcutaneous injection, and was well tolerated.