(62r) Evaluation of Intradermal Drug Delivery Devices

Background: Traditional vaccine injections use the Mantoux method which involves inserting a hypodermic needle at an angle into the skin such that it delivers the drug intradermally. However, the reliability of this method in terms of localizing drug within the skin requires special training and is variable from person to person.

Objective: The objective of this study was to evaluate three intradermal injection devices to quantify the amount of drug they deliver into skin and to determine the reliability of drug distribution within the dermis.

Methods: The three devices evaluated in this study were: traditional Mantoux injection using a 28-gauge hypodermic needle administered by an experienced user, a custom intradermal injection adapter prototype with a 28-gauge hypodermic needle and an 850 µm long hollow microneedle. Ten male feeder pigs were used in this study with IACUC approval. To quantify the amount of drug delivered into skin, 100 µl of sulforhodamine B was injected into the skin of anesthetized pigs using the different injection devices. The dye left on the skin surface and in the device was collected and quantified using a spectrofluorometer. A mass balance was then used to determine the amount of drug delivered into skin. To determine the distribution of dye within the skin, 100 µl of trypan blue was injected into the skin of freshly euthanized pigs. A skin biopsy was immediately taken followed by freezing the sample. Histology sections of the samples were taken and imaged under brightfield microscopy.

Results: The spectrofluorometer quantification results indicated that the traditional Mantoux method administered by an expert professional, intradermal adapter and hollow microneedle all delivered > 95% of sulforhodamine into skin. The histology results indicated that all injection devices were able to localize dye in the dermis with similar reliability with means ranging from 84-92% of dye in the dermis for the three delivery methods.

Conclusions: The results of this study show that the intradermal adapter and hollow microneedles are as effective as traditional Mantoux method in delivering drug into skin. In this study, all three delivery methods reliably delivered drug to the dermis. However, it must be noted that the reliability of Mantoux injection depends on the user whereas the other two devices are designed to reduce user variability. The results of this study will be used to further optimize the prototype devices to increase reliability and improve injection efficacy.