1. Biopharmaceutics studies the relationship between drugs and biological systems, taking into account how pharmaceutical factors influence bioavailability. These factors include active pharmaceutical ingredient modifications, physical conditions, excipients, dosage forms, and production methods. 2. Bioavailability refers to the amount of active drug that reaches systemic circulation. It is affected by factors that influence absorption and can be determined by comparing drug plasma concentrations with intravenous administration. Bioequivalence indicates same drug concentrations in plasma and tissues for different formulations, while therapeutic equivalence means same therapeutic and adverse effects. Differences in bioavailability between formulations can have clinical significance.

1. BIOPHARMACEUTICS
1. Introduction
The scientific biopharmaceutical direction is based on experimental studies. It is currently
being developed as a modern pharmaceutical theory that studies the relationship between a
drug as a particular physicochemical system and a macroorganism (biological system), taking
into account the influence of pharmaceutical factors on bioavailability. Pharmaceutical
factors include: "simple chemical modification" of API (active pharmaceutical ingredient) and
auxiliary substances, physical condition of APIs in product, nature and quantity of excipients,
type of dosage form, ways of introduction into the body and technological methods used in
production.
The tasks of biopharmacy are:
1. Research on the effect of "simple chemical modification" of APIs on their release,
absorption processes and the stability of the properties of the drug itself.
2. Investigation of the influence of the physical condition of APIs on its release and
absorption rate, on the stability and properties of the drug.
3. Investigation of the influence of the dosage form on the bioavailability of the API
contained in it.
4. To study the influence of the nature and quantity of excipients on the bioavailability,
stability and properties of the API.
5.Research on the influence of manufacturing processes and production methods on the
bioavailability of APIs and the properties of medicinal preparations.
6. Investigation of the influence of the ways of introduction of dosage forms in the organism
on the bioavailability of APIs and the effectiveness of medicinal preparations.
Thus, the biopharmacy interest circle encompasses a wide range of interrelated issues that
determine the effectiveness of treatment therapy, which can be conditionally divided into
experimental and clinical biopharmacy. From the point of view of pharmaceutical
technology, the most important task of biopharmacy is to study the influence of variable
(technological) factors on the processes of absorption of APIs from the drug. Recognition of
the biological importance of variable factors has made it possible to consider the drug as a
complex physico-chemical system whose constituent ingredients determine the healing
effect.
Therapeutic or prophylactic activity of any API is due to its chemical structure and physico-
chemical properties. The pharmacological activity of the substance is also significantly
affected by the "secondary properties" in the preparation of the drug as a result of the
acquired, purposeful technological intervention. For example, changing the degree of
dispersion (particle size), selecting excipients, making the optimal dosage form.

2. The physico-chemical properties of the API, technological processes and auxiliary substances,
integrated in the dosage form, have been accepted in the literature by the conditional term
"pharmaceutical factors". The latter study is mandatory in terms of biopharmacy, due to their
substantial influence on the dynamics of bioavailability of APIs, their stability in the drug
storage process and many other indicators. Pharmaceutical factors also combine ways of
administration of dosage forms into the body.
The chemical state of a substance is very often described in the literature as a simple chemical
modification. The term "simple chemical modification" refers to the use of API and auxiliary
substances in the form of acids, bases, various salts and other compounds, in which the part
responsible for the pharmacological effect of the molecule is completely preserved. For
example penicillins, alginic acid and its sodium and potassium salts, codeine base and codeine
phosphate, novocaine base and novocaine hydrochloride and others.
The physical condition of a substance from a biopharmaceutical point of view includes:
polymorphism; Degree of dispersion (particle size); Aggregate state; Shape of crystals;
Electrophysical, optical and other characteristics that determine the surface properties of the
substances and may cause therapeutic inadequacy of the drugs and or their side effects.
Dosage form - this is a rational, pharmaceutically acceptable form of drug for administration
and keeping the substance, which ensures its optimal therapeutic effect with a minimum of
side effects. Biopharmaceutical studies show that not only the therapeutic efficacy of an API
is essentially dependent on the form of the drug, but also the adverse reactions of the
organism and the side effects of the drug. Sometimes only a change in the form of medication
is enough to achieve the desired result, avoid drug side effects and opposite also occurs. For
example: long-term therapy using indomethacin suppositories is carried out without
complications, with a good therapeutic effect, while the use of indomethacin tablets is
accompanied by side effects: headache, dizziness, nausea, vomiting, loss of appetite;
Excipients - This is a wide range of materials of natural and synthetic origin that can perform
various functions in the manufacturing and storage of dosage forms: solvents, bases,
surfactants, thickeners, stabilizers, emulsifiers, preservatives, colorants, etc.
Technological or industrial processes involve special methods of making medicines and a
variety of related, yet strictly defined methods and operations. Biopharmacy has given a
theoretical basis for technological processes in a complex system - "medicine", in terms of
their impact on the pharmacokinetics of APIs. In the process of biopharmaceutical studies, it
became possible to determine that one of the reasons for the difference in therapeutic
equivalence of drugs is the variety in the methods of their preparation.
2. Bioavailability
Drug bioavailability is the fraction of the administered dose that reaches the systemic circulation.
For the clinician, the most relevant consideration is the percentage of active drug that reaches the
central compartment. Bioavailability does not take into account the rate at which the drug is

3. absorbed. Bioavailability is affected by factors that influence absorption. The absolute availability
of a drug may be determined by comparing the respective areas under the plasma concentration
curve (AUC) to intravenous administration.
Bioavailability of a drug is largely determined by the properties of the dosage form, which depend
partly on its design and manufacture. Differences in bioavailability among formulations of a given
drug can have clinical significance; thus, knowing whether drug formulations are equivalent is
essential.
Pharmaceutical equivalence (chemical equivalence) - indicates that drug products contain the
same active compound in the same amount and meet current official standards; however, inactive
ingredients in drug products may differ.
Bioequivalence indicates that the drug products, when given to the same patient in the same
dosage regimen, result in equivalent concentrations of drug in plasma and tissues.
Therapeutic equivalence indicates that drug products, when given to the same patient in the same
dosage regimen, have the same therapeutic and adverse effects.
Bioequivalent products are expected to be therapeutically equivalent. Therapeutic
nonequivalence (eg, more adverse effects, less efficacy) is usually discovered during long-term
treatment when patients who are stabilized on one formulation are given a nonequivalent
substitute.
Sometimes therapeutic equivalence is possible despite differences in bioavailability. For example,
the therapeutic index (ratio of the minimum toxic concentration to the median effective
concentration) of penicillin is so wide that efficacy and safety are usually not affected by the
moderate differences in plasma concentration due to bioavailability differences in penicillin
products. In contrast, fordrugs with a relatively narrow therapeutic index, bioavailability
differences may cause substantial therapeutic nonequivalence.