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Pharmacokinetics is based on mathematical modeling that places great emphasis on the relationship between drug plasma concentration and the time elapsed since the drug's administration. Pharmacokinetics is the study of how an organism affects the drug, whereas pharmacodynamics (PD) is the study of
The absorption rate constant K a is a value used in pharmacokinetics to describe the rate at which a drug enters into the system. It is expressed in units of time −1. [1] The K a is related to the absorption half-life (t 1/2a) per the following equation: K a = ln(2) / t 1/2a. [1] K a values can typically only be found in research articles. [2]
The converse is true in a basic medium. For example, Naproxen is a non-steroidal anti-inflammatory drug that is a weak acid (its pKa value is 5.0). The gastric juice has a pH of 2.0. It is a three-fold difference (due to log scale) between its pH and its pKa; therefore there is a 1000× difference between the charged and uncharged concentrations.
The stomach's acidic pH and the subsequent alkalization in the intestine modifies the degree of ionization of acids and weak bases depending on a substance's pKa. [1] The pKa is the pH at which a substance is present at an equilibrium between ionized and non-ionized molecules. The Henderson–Hasselbalch equation is used to calculate pKa.
Distribution in pharmacology is a branch of pharmacokinetics which describes the reversible transfer of a drug from one location to another within the body.. Once a drug enters into systemic circulation by absorption or direct administration, it must be distributed into interstitial and intracellular fluids.
The first pharmacokinetic model described in the scientific literature [2] was in fact a PBPK model. It led, however, to computations intractable at that time. The focus shifted then to simpler models, [3] for which analytical solutions could be obtained (such solutions were sums of exponential terms, which led to further simplifications.)
Lipinski's rule of five, also known as Pfizer's rule of five or simply the rule of five (RO5), is a rule of thumb to evaluate druglikeness or determine if a chemical compound with a certain pharmacological or biological activity has chemical properties and physical properties that would likely make it an orally active drug in humans.
In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase [1] whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase ( EC 2.7.11.11 ).