Doxycyclin prevents leptospirosis. If you need to wade into floodwaters, take this antibiotic beforehand. 100mg should be below P10 (doctors/pharmacists/nurses: please correct me if I'm wrong).
Just remember that Doxycylin contraindicated for children under 8 and pregnant/breastfeeding women.
BTW eto yung sa EDSA-Petron na butas na namention kanina: