Bioactivation is a crucial step in the activity of certain pharmaceuticals. Often, the parent form of the drug is not the active form and it needs to be metabolized in order to produce its therapeutic effects. In other cases, bioactivation is not necessarily needed for drugs to be active and can instead produce reactive intermediates that initiate stronger adverse effects than the original form of the drug. Bioactivation can occur through the action Phase I metabolic enzymes, such as cytochrome P450 or peroxidases. Reactive intermediates can cause a loss of function in some enzymatic pathways or can promote the production of reactive oxygen species, both of which can increase stress levels and alter homeostasis.