drug metabolism is the process by which the body breaks down medications. the liver plays a major role in metabolism especially a group of enzymes known as cytochrome p-450. drug interactions can occur when two or more drugs inhibit or induce a p-450 reaction and the drugs do not metabolize as quickly as they should. nicotine is a "drug" also and is known to induce the p-450 system. individuals with liver disease may also have insufficient levels of p-450 enzymes. the result is that drug levels can remain high in the bloodstream and cause more side effects. genetic factors also play a role in drug metabolism. the metabolic rate can vary significantly from person to person and drug dosages that work quickly and effectively in one individual may not work well for another or cause build-up and more side effects. infants and elderly patients have a reduced abilty to metabolize certain drugs so we often adjust their med dosage. but we find that people with fm [fibromyalgia] seem to act like "geriatric patients" in terms of sensitivity to meds and side effects (and metabolism? ) and often require lower doses than the "normal" non-fm adult. certain foods such as grapefruit juice and certain meds taken on an occasional basis can inactivate or lessen the metabolic activity of p-450s and can cause apparent fluctuations in response/tolerence to regular prescribed meds. we with fibro always seem to develop tolerances and intolerances to meds that we previously did well with which is frustrating to say the least. so there are different metabolism tolerance and intolerance factors that can cause us to have "reactions" to our meds. .
what affects drug metabolization from dose to dose?