Microneedle patch designs to increase dose administered to human subjects

Microneedle (MN) patches are being developed for many different kinds of drugs, but are often limited to delivering sub-milligram doses. This is because larger patches can be more difficult to apply to the skin, and acceptability of larger MN patches by human subjects has received limited study. Here, we fabricated 18 different large MN patch designs by laser microfabrication with different MN length (800–1500 μm), number of MNs (225 to 900 MNs per patch), space between MNs (600–1100 μm), and MN base diameter (200–250 μm). After manual application of these patches to human participants, we assessed dose delivery efficiency, total dose delivered, dose delivered per MN, depth of MN penetration and whole-MN delivery efficiency. We found that all of these parameters generally increased with decreased MN length, increased number of MNs (among those ≤1000 μm in length) and increased MN-MN spacing. All MN patch designs caused less pain than a pin prick sensation and were generally considered acceptable by the study participants. The MN patches induced mild, or sometimes moderate, transient erythema on skin. Study participants showed higher preference for MN patches for long-acting contraception compared with conventional options, indicating strong interest and acceptability of MN patches in this study.