There can be a real benefit to isomer drugs. They get prescribed way more than they need to, no question, but that doesn't make them entirely useless. For exam

There can be a real benefit to isomer drugs. They get prescribed way more than they need to, no question, but that doesn't make them entirely useless. For example, desvenlafaxine (Pristiq) is the R-isomer of venlafaxine (Effexor). You'd think it would be a useless me-too drug, but in fact it's metabolized differently, which affects people with CYP450 mutations. Ultrarapid metabolizers will end up with way too little Effexor in their system, whereas Pristiq will work fine for them. Other way around with poor metabolizers: they don't metabolize Effexor well enough, so they'll get worse side effects. (See http://psychopharmacologyinstitute.com/antidepressants/snris/venlafaxine-desvenlafaxine-differences-similarities/ http://psychopharmacologyinstitute.com/antidepressants/snris... and specifically http://psychopharmacologyinstitute.com/wp-content/uploads/12-Metabolizer-types.png. http://psychopharmacologyinstitute.com/wp-content/uploads/12...) Ideally we'd all know our CYP450 profile, or our doctors would, so they could prescribe older and cheaper drugs when they work well enough, and save the new expensive stuff for patients who need it. Maybe someday medicine will come around to using the tools it already has at hand. Sigh.