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ASCPT

Poster - May 2025

The Dorsal Forearm as a Novel Target for Intramuscular Injections: Clinical Pharmacokinetic Results

Presenter: Thomas Krol, Pharm D

Presented at ASCPT 2025 Annual Meeting on May 28th

Poster Details

IM administration of naloxone into the dorsal FOREARM muscle has a PK profile approximately equivalent to IM injection into the thigh, setting the stage for a new convenient IM device.

Naloxone 2 mg PoC - IM Forearm
(compared to IM into the thigh – NIH data)

Background

The dorsal forearm represents a potential viable location for a convenient wearable device for the administration of intramuscular (IM) injections, but this site has not previously been formally targeted for this purpose. The objectives of this study were to administer naloxone via IM injection into the dorsal forearm, characterize the pharmacokinetic (PK) profile of this injection site and mode, and compare to that of an IM injection at a standard site.

Methods

1. Clinical study - outpatient, open-label, single period, single treatment, single dose proof-of-concept (PoC) trial in 12 healthy subjects.

2. After screening, participants provided a time zero (pre-dose) blood sample and then administered 2 mg naloxone HCl as an IM injection in the extensor digitorum communis (EDC) muscle of the dorsal FOREARM.

3. Serial blood (plasma) samples obtained from contralateral arm at the following time points: 5 minutes prior to dosing and 5, 10, 15, 20, 30, 40, and 50 minutes and 1, 1.25, 1.5, 2, 3, 4, and 6 hours post-dose.

4. Plasma naloxone concentrations were determined using a validated LC MS/MS assay..

5. PK parameters generated from the resultant plasma naloxone concentration-time data for each IM injection site using WinNonLin 8.4. (PK data for 2mg IM naloxone into the thigh were obtained directly from NIDA for comparison.)

Results

Means and ranges of the PK profile of naloxone administered IM in the forearm:
Cmax 5.3 ng/mL (2.21 - 11.07)
Tmax 0.29 h (0.08 - 0.67)
AUC[0-∞] 7.96 ng*h/mL (5.85 to 10.68)
T1/2 1.36 h (0.95 - 1.74)

Relative bioavailability of naloxone administered into the dorsal forearm was 87% compared to IM naloxone administered in the thigh. PK variability was similar for the two IM injection sites. Subjects noted minimal discomfort with the forearm injection and no adverse neurovascular events.

Patient Demographics

Representative Injections

  • IM to forearm muscle well tolerated.

  • No effect on motor or sensory based on verbal and physical assessments

  • 3 AE’s: 2 vasovagal; 1 dizziness/HA

Safety

  • Naloxone IM into forearm is approximately equivalent into IM injection to thigh

  • Forearm site was associated with minimal discomfort or complications

  • Team will proceed with device development to deliver IM injection into forearm

Conclusions

Thomas Krol
Bryan Beutel
Carlos Fierro
Scott Weir

Study sponsored by STAT Therapeutics, Inc.

References available upon request 

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