They are digestion, delivery, metabolism, bioavailability, and elimination. The method of administration and how the bodily organs work impact each of these processes. So, according to pharmacokinetics definition, it is the activity of drugs in the body over a period of time, including the processes by which drugs are absorbed, distributed in the body, localized in the tissues, and excreted. PK bioanalysis is an integral part of drug development. PK investigations might be exploratory or comprehensive and formal. PK studies in clinical trials is conducted to investigate a drug’s absorption, distribution, metabolism, and excretion. One of the most crucial methods, i.e. noncompartmental pk analysis (NCA), gives the most basic pharmacokinetic data for a medication (i.e., peak concentration and elimination half-life). NCAs are critical for characterizing novel pharmacological compounds and can assist in guiding development at every step. Let us go through these essential pk assays steps:
Absorption/ Digestion
A vital aspect of the pharmacokinetic study is absorption, which is the process through which medication enters the bloodstream from its introduction into the body. The stomach or intestinal mucosa is usually where enteral medications are absorbed. Any drug given orally falls within this category. The stomach contents, drug solubility, and blood flow are all variables that may affect how well enteral drugs are absorbed.
The parenteral route of absorption, which usually refers to drugs that are injected, is another method. Depending on the type of injection, the rate of absorption will change. This category includes drugs used intravenously. Since they are administered directly into the circulation, they are absorbed most quickly. Additionally, intramuscular drugs, or those injected deeply into the muscles, are more quickly absorbed than subcutaneous injections, where pharmaceuticals are administered.
Delivery/ Distribution
Medication distribution refers to releasing a drug into the body’s blood and tissues while still unmetabolized. It is one of the important principles of pk study. The distribution of a drug’s efficacy or toxicity in specific tissues contributes to the lack of a relationship between plasma levels and observed effects.
Metabolism
“Metabolism” refers to the chemical processes transforming medicines into less harmful molecules. Metabolites are the results of these chemical processes.
Enzymes catalyze the processes, which mainly occur in the liver but also affect the gut wall, lungs, and blood plasma.
Compounds consisting ofÂ
- The majority of non-polar compounds are soluble in lipids but insoluble in water.
- Polar compounds often dissolve in water but are insoluble in lipids.
Producing metabolites that consist of polar molecules means that they can be excreted in body fluids such as urine and bile.Â
Bioavailability
The amount and pace at which the active moiety (drug or metabolite) enters the systemic circulation and subsequently reaches the site of action are referred to as bioavailability -an critical step of pk testing.
A drug’s bioavailability is substantially influenced by the dosage form’s characteristics, which are partially dictated by how it was made and designed. Knowing if medication formulations are similar is crucial because variations in bioavailability between different drug formulations may have therapeutic implications.
- Chemical equivalency states that drug products have the same active component in the same quantity and adhere to established criteria, although inactive substances may vary. According to bioequivalence, the drug products produce equal drug concentrations in plasma and tissues when administered to the same patient according to the same dose regimen.
- Therapeutic equivalence means that medication items have the same beneficial and harmful effects when administered to the same patient under the same dosing regimen.
Drug elimination/Excretion
By the end of pharmacokinetic testing, drug excretion from the primary organs is done to eliminate water-soluble compounds in the kidneys. To the extent that a medication is not reabsorbed from the GI tract, the biliary system aids in excretion.
The majority of drug excretion is caused by renal filtration. Nearly all the water and electrolytes are passively and actively reabsorbed from the renal tubules back into circulation. About one-fifth of the plasma reaching the glomerulus is filtered via pores in the glomerular endothelium.
