Subcutaneous Infusions of High-Dose Benzathine Penicillin G (SCIP) is Safe, Tolerable and Potentially Suitable for Less Frequent Dosing for Rheumatic Heart Disease Secondary Prophylaxis

Abstract

Introduction: Since 1955, the recommended strategy for rheumatic heart disease (RHD) secondary prophylaxis has been benzathine benzylpenicillin G (BPG; 1.2 MIU) injections administered intramuscularly. Due to dosing frequency, pain and programmatic challenges, adherence remains suboptimal. Our team has previously demonstrated that BPG delivered subcutaneously at a standard dose is safe, tolerable and has favourable pharmacokinetics, setting the scene for improved regimens with less frequent administration. Methods: The safety, tolerability, and pharmacokinetics of SubCutaneous Infusions of high‐dose BPG (SCIP) was assessed in 24 healthy adult volunteers assigned to receive either 3.6, 7.2 or 10.8MIU (3, 6 and 9 times the standard dose, respectively) as a single subcutaneous infusion. Delivery of the BPG to the subcutaneous tissue was confirmed with ultrasonography. Safety assessments, pain scores and penicillin concentrations were measured for 16 weeks post dose. Results: Subcutaneous infusion of penicillin (SCIP) was generally well tolerated with all participants experiencing transient, mild infusion‐site reactions. Prolonged elevated penicillin concentrations were described using a combined zero‐ (44 days) and first‐order (t½=12 days) absorption pharmacokinetic model. Higher BMI significantly impacted the model. In simulations, time above the conventionally accepted target concentration of 20ng/mL (0.02 μg/mL) was 57 days for 10.8MIU delivered by subcutaneous infusion every 13‐weeks compared with 11 days for standard 1.2MIU intramuscular dose (i.e., 63% and 39% of the dosing interval, respectively). Conclusion: High dose SCIP (BPG) is safe, has acceptable tolerability and may be suitable for up to 3 monthly dosing intervals for secondary prophylaxis of RHD.