Tomcat (Paederus sp.) venom can bring a condition called dermaconecrosis. Initially, paederin toxins was thought that come from the body of Tomcat (Paederus sp.). However, based on Piel's research, the genes come from biosynthesis of tomcat (Paederus sp.) venom is more approach to Pseudomonas aeruginosa genes than body itself. In other fact, Pseudomonas aeruginosa can secrete enzymes metalloprotease (MMP), especially extracellular MMP-2 and MMP-9. MMP-2 and MMP-9 are gelatinase that can destroy the gelatin on human skin. There has been no previous report about the treatment of dermatitis paederus based on the mechanism of action except for the use of corticosteroids as symptomatic drugs. Because of that, researcher hypotheses that MMP-2 and MMP-9 have a role on dermatitis paederus and doxycycline can inhibit that process as MMP inhibitor and antibiotics component. The research design is quasi-experimental research, in vitro with a post-test only control group design. The research steps are Tomcat (Paederus sp.) venom extraction, doxycycline solution preparation, and electrophoresis of gelatin zymografi. The independent variables are induction of Tomcat (paederin sp.) venom and the doses of doxycycline, while the dependent variable is the density of the gel. Gel density was measured using densitometry software ImageJ and calibrated as optical density. This study describes the first time the mechanism Paederus dermatitis caused by MMP-2 and MMP-9, so that the first line of therapy that can be used is doxycycline with an effective dose of 10 mM in vitro.