The side effects of omeprazole mimic, in a milder form, the clinical manifestations of primary carnitine deficiency, a genetic disease caused by mutations in the gene coding for OCTN2; at the same time the toxicity exerted by mercurials can be explained as alteration of cell homeostasis due to impaired transport of nutrients and cofactors or to altered redox sensing function of OCTN2. Here, SLC22A5 is linked to hereditary disease.