Comparative efficacy of once-daily versus twice-daily doxycycline regimens in dogs naturally infected with Ehrlichia canis: A randomized clinical trial

Abstract

This prospective, randomized clinical trial compared the therapeutic efficacy and rate of platelet recovery of doxycycline 10 mg/kg once daily (SID) (Group A, n=17) versus 5 mg/kg twice daily (BID) (Group B, n=12) in 29 dogs naturally infected with Ehrlichia canis . Using a "treat-to-target" protocol that mandated both molecular clearance and platelet normalization prior to cessation, results showed that while both regimens achieved 100% molecular clearance, the BID regimen demonstrated significantly more rapid hematological recovery (P < 0.05 at Days 7 and 14) and required a significantly shorter median treatment duration (28.5 days vs. 39.0 days; P = 0.015). Notably, delayed molecular clearance (>28 days) was observed exclusively in the SID group, and post-treatment recrudescence was detected in two dogs at Day 98. We conclude that the 5 mg/kg BID protocol offers superior pharmacodynamic performance, and a "treat-to-target" strategy involving long-term monitoring is recommended over a fixed 28-day course to ensure complete clinical and parasitological resolution.