Biopharmaceutics

Biopharmaceutics: 

the study of how the physicochemical properties of drugs, dosage forms and routes of administeration affect the rate and extent of the drug absorption.

Thus, biopharmaceutics involves factors that influence the: 1) protection and stability of the drug within the  product; 2) the rate of drug release from the product; 3) the rate of dissolution of the drug at the absorption site; and 4) the availability of the drug at its site of action . 

nADME: is an acronym in pharmacokinetics and pharmacology for absorption, distribution, metabolism, and excretion, and describes the disposition of a pharmaceutical compound within an organism.

nPharmacokinetics: The study and characterization of the time course (kinetics) of drug absorption, distribution, metabolism and elimination (ADME).

nAbsorption: is the process of a substance entering the body.
nDistribution: is the dispersion  of substances throughout the fluids and tissues of the body.
nMetabolism: is the irreversible transformation of parent compounds into daughter metabolites.
nExcretion: is the elimination of the substances from the body.

nBioavailability: The rate and extent of drug absorption.

nBioavailable dose: The fraction of an administered dose of a particular drug that reaches the systemic circulation intact. 

nPlasma level-time curve:

nThe plasma level-time curve is generated by measuring the drug concentration in plasma samples taken at various time intervals after a drug product is administered.

nThe concentration of drug in each plasma sample is plotted against the corresponding time at which the plasma sample was removed.

nDrug Product Performance Parameters:

1- Minimum effective concentration (MEC): The minimum concentration of drug needed at the receptors to produce the desired pharmacologic effect.

2- Minimum toxic concentration (MTC): The drug concentration needed to just produce a toxic effect.

3- Onset time: The time required for the drug to reach the MEC.

4- Duration of action: The difference between the onset time and the time for the drug to decline back to the MEC.  

5- The time of peak plasma level: The time of maximum drug concentration in the plasma and is proportional to the rate of drug absorption.

6- The peak plasma level: The maximum drug concentration, usually related to the dose and the rate constants for absorption and elimination of the drug.

7- Area under the curve: It is related to the amount of drug absorbed systemically.