Systemic Bioavailability of Sublingual Atropine Ophthalmic Solution: a Phase I Study in Healthy Volunteers with Implications for Use as a Contingency Medical Countermeasure.

INTRODUCTION: Atropine sulfate is an FDA-approved medical countermeasure (MCM) for the treatment of organophosphorus nerve agent and organophosphate pesticide toxicity. Sufficient MCM supplies must be available in an incident involving a mass human exposure either from an accidental chemical release or a terrorist attack. METHODS: We performed a randomized, 3-sequence, 3-period phase I crossover study to assess the bioavailability and pharmacokinetics (PK) of a single dose (0.5 mg and 1.0 mg) of 1% ophthalmic atropine sulfate solution administered sublingually to 15 healthy adult volunteers. The primary endpoint was evaluation of the bioavailability of each of the two sublingual doses against a 1.0 mg reference intravenous (IV) atropine dose. Secondary endpoints included the safety and tolerability (xerostomia scale) of atropine sulfate administered sublingually. RESULTS: Sublingual atropine was safe (no severe AEs or SAEs were reported with either dose) and well tolerated, with a single subject reaching maximum xerostomia on a single dosing day. The geometric mean AUC∞ was 286.40, 493.81, and 816.47 min*ng/mL for the 0.5 mg and 1.0 mg sublingual doses, and the 1.0 mg IV dose, respectively. Compared to IV administration, the 1.0 mg sublingual dose produced 0.60 (90% CI: 0.55-0.66) of the overall concentration of atropine over time (AUC∞). CONCLUSION: Sublingual atropine sulfate 1% ophthalmic solution may be an alternative formulation and route of administration combination which expands the capacity and dosing options of atropine as a nerve agent MCM.