Lucas V. answered • 04/23/19
Pre-Med./Nursing | 92-%tile MCAT | Accepted to MD program
The term "processed" needs to be clarified in the question. I will assume in this context that the stated term is in reference to either of two closely-related pharmacokinetic processes: metabolism and elimination. These are the biological mechanisms that process drugs/medications/chemical substances taken exogenously. Essentially all administered drugs will involve (1) a metabolic/biotransformation step by the liver, and (2) a subsequent elimination phase in the kidney & urinary systems; with exceptions. A major purpose of hepatic metabolism is to enhance/facilitate renal excretion by the addition or exposure of polar moieties in the chemical structure of a drug that, in general, will promote greater water (aqueous) solubility for urinary elimination.
So, a quick, but disadvantageous, way to determine the pharmacokinetic profile of a drug is to use a drug reference source that will outline the metabolism and elimination properties associated with a respective drug. However, a deeper understanding of these pharmacological mechanisms is more valuable to fully appreciate the biological implications of drug activity/interactions.
The liver is the major organ/tissue system responsible for drug metabolism/detoxification due to the high concentration of drug-metabolizing enzymes in the smooth endoplasmic reticulum of hepatocytes. Correspondingly, following oral administration, drugs are absorbed/secreted by the stomach and drain into the portal venous system which first circulates into the hepatic vasculature prior to emptying into the inferior vena cava. Thus, drugs taken orally may undergo first-pass metabolism before being distributed to systemic tissue sites.
Metabolism functions to (1) deactivate drugs/chemical substances into inactive metabolites, either directly or by facilitated-conjugation elimination, or (2) elicit bioactivation of a drug compound into active/reactive metabolites (ex., clopidogrel). Much of hepatic-mediated metabolism is carried out by the catalytic activity of the enzymatic superfamily cytochrome P450 and is accordingly responsible for a large majority of drug metabolism in humans.
Aspirin (ASA) and acetaminophen (APAP) have unique pharmacokinetic aspects and drug-administration implications that will not be discussed here. The case for ibuprofen - a non-selective, reversible inhibitor of cyclo-oxygenase (COX-1 / COX-2) activity - involves primarily hepatic (liver) oxidative metabolism by CYP enzymes (ex., CYP2C9 isoform) into inactive metabolites which then undergo renal/urinary excretion.
Understanding the principles of pharmacokinetics more exhaustively is ultimately the "quickest" way to appreciate the biological processing mechanisms and locations involved with drug metabolism/clearance. I hope this provided some insight. I will be glad to discuss the case for aspirin or acetaminophen, if requested. This topic is quite complex to narrow down a useful heuristic.
**Please note that other tissue systems can participate in metabolic and elimination processes and that several metabolic steps can be involved in the biotransformation reactions of a drug -> inactive/active metabolite; but, the case in general is as described.
