The Eagle effect, Eagle phenomenon, or paradoxical zone phenomenon, named after Harry Eagle who first described it, originally referred to the paradoxically reduced antibacterial effect of penicillin at high doses,  though recent usage generally refers to the relative lack of efficacy of beta lactam antibacterial drugs on infections having large numbers of bacteria.  The former effect is paradoxical because the effectiveness of an antibiotic generally rises with increasing drug concentration.
__TOC__