there are no magic pills (_or injectables_) with 100% results, multiple sustainable strategies & clever tactics are required on the journey to higher purity; the parasite can adapt and grow resilient, thru upregulating the host's endogenous cytochrome p450 (metabolises drugs) for example or potentially by mutating or hiding behind thicker biofilms; 

in addition, as the parasite hivemind matures and takes over more supply chains, previously effective compounds will either stop being available or become contaminated or something else... the simplest & cheapest method is prolonged fasting;