Samenvatting
Summary Pharmaceutical Technology And Biopharmacy 1 (WBFA017-05)
- Instelling
- Rijksuniversiteit Groningen (RuG)
Summary of the lectures and documents provided in the course PTBP1
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Voorbeeld van de inhoud
▪ Biopharmaceutics is the field that investigates and describes everything that happens with amedicinal product and the active substance between the moment of administration, the
moment it exerts its action and the moment it is eliminated from the body.
▪ Biopharmaceutics connects the physicochemical properties of an active substance and its
dosage form with its action and fate in the living organism.
o It encompasses pharmacokinetics, pharmacodynamics and drug delivery technology.
o The route of administration, the way the active substance is released from the dosage
form, and the way the body handles (absorbs, distributes, metabolises and excretes) the
active substance, together determine its (duration of) action, its efficacy and the
occurrence of adverse effects.
▪ The major routes of administration: parenteral, oromucosal, oral, rectal, dermal, nasal,
pulmonary and ocular.
1.1 From medicinal product to effect and beyond
1.1.1 Design of the medicinal product
A medicinal product (medicine or drug product, formulation or dosage form) is characterised by the
quantitative composition (encompassing both the active substance(s) and excipients), the
physicochemical state of the active, excipients and medicinal product as a whole, as well as the
structure in which the different components are present in the medicinal product →
Functionality→intended use.
The functionality of the medicinal :
The technical terms encompass aspects such as stability, uniformity of dosage and microbiological
quality of the product.
The biopharmaceutical functionality of a medicinal product relates to aspects such as the drug release
profile, suitability of the medicinal product for administration via the intended route and ability of the
active substance to reach the site of action.
Medicinal products exist in a variety of forms, to be used for different routes of administration, aiming
at either a systemic or a local effect.
o systemic effect, the oral and parenteral routes are the most frequently used. Alternatively,
medicinal products can be given through rectal, transdermal, nasal or pulmonary administration
to achieve a systemic effect.
o Rectal and pulmonary administration may also be applied for a local effect. Medicinal products
administered to the eye, nose and ear are mostly used for a local effect.
1.1.2 Pharmaceutical availability and bioavailability
▪ active substance is not administered directly at its site of action.
o transport is necessary from the site of administration to the site of action.
o The first step in this process is the release of the active substance from the dosage form.
The delicate interaction between the physicochemical properties of the active substance
and its dosage form as well as the physiological conditions at the site of release,
determine the extent and rate at which release will occur.
, ▪ the active substance is released from its administration form in a dissolved state or dissolve in
an aqueous environment.
o Only in the dissolved state, can an active substance pass biological membranes
separating the site of administration from the systemic circulation (the blood
circulation) via which transport to the site of action occurs.
▪ The pharmaceutical availability: The fraction of the administered active substance that
dissolves in the aqueous fluid adjacent to the biological membranes and thereby becomes
available for passing them.
▪ Bioavailability: The fraction of the total amount of the administered active substance that
ultimately reaches the systemic circulation in an unchanged form.
Bioavailability determined by:
- the characteristics of the active substance and the medicinal product (which may, for
example, determine the dissolution rate)
- the chosen route of administration (different membranes show different permeability)
- the administration conditions (e.g. the concomitant intake of food with oral medicine
administration)
▪ Absorption: The transport of the dissolved active substance over the membranes to the blood
circulation.
o The extent and rate of absorption are determined by several factors :
- The size and charge of the active substance molecule
- Its lipophilicity
- The volume available for active substance dissolution
- The surface and permeability of the absorbing membrane
- The presence of metabolising enzymes and, in the case of active transport
- The presence of transporters.
As a consequence, poor bioavailability may be caused by incomplete dissolution of the active substance,
by poor permeation over the absorbing membrane, or by metabolism during absorption.
Absorption → the systemic circulation → transport to the site of action occurs →once arrived, the
active substance can exert its action → during and after transport as well as during and after exerting its
action, distribution, metabolism, and excretion of the active substance occur.
▪ The rate of absorption and elimination plus the volume of distribution determine the time and
height of the peak concentration of the active substance in the blood.
The following medicine-related physicochemical aspects may influence the release and absorption
(bioavailability) of an active substance and thereby its final efficacy:
• The chemical form of the active substance (free acid or base, a salt )
• The physical state of the active substance (particle size, crystal modification)
• the nature and quantity of excipients and their interaction with the active substance;
• the dosage form ( a solid dosage form or a solution);
• the route of administration (oral, parenteral, rectal);
• The pharmaceutical formulation (ethe medicinal product, the quantitative composition, or the
structure in which the active substance and excipients are present in the dosage form).
,Next to these factors other aspects, related to human physiology and external factors, may affect
release and absorption of the active substance too.
• the interaction with food or concomitantly administered other medicines;
• the presence of enzymes that metabolise the active substance before absorption.
• the volume of the fluid, available at the site where the medicine dissolves;
• the presence of endogenous substances (such as bile salts) that affect the solubility of active
substances;
• variations in gastro-intestinal motility;
• blood flow variations at the site of absorption.
In summary, biopharmaceutics relates the physicochemical characteristics of an active substance, the
functionalities and a medicinal product and the route of administration to the performance in the living
organism and to the efficacy and safety of the medicinal product. The biopharmaceutical characteristics
are important aspects in the design of new medicinal products. They should be considered during the
different stages of research and development as well as during the full subsequent lifetime of a
medicine.
To achieve the desired therapeutic effect of an active substance, an adequate administration form in
relation to the chosen route of administration must be used. The current pharmaceutical- technological
knowledge offers possibilities to achieve optimal absorption of an active substance. Optimal in this
context means: reliable, with a reproducible fraction absorbed and, if necessary, with a desired control
of the release profile. Already small variations in excipients may significantly influence the
pharmaceutical and biological availability and hence the therapeutic and adverse effects of a medicine.
This applies to systemic as well as local administration. Furthermore, it is to be realised that the
equivalence of these aspects may be of paramount importance for generic substitution.
1.1.3 Pharmacokinetics, pharmacodynamics and toxicology
, Oral Solids (4.1 t/m 4.3)
▪ Solid oral dosage forms are dosage forms that are usually swallowed to release the active
substance at one or more sites of the digestive tract mainly for a systemic effect
▪ Solid dosage forms can be a powder or a mixture of powders, often further processed into
tablets or hard capsules
▪ Powders as such or encapsulated into hard shells (capsules) are alternatives to tablets. They are
needed for example to obtain appropriately sized dosage units for children.
▪ Stability is one of the main advantages of solid dosage forms compared to liquid ones. There is
no need for preservatives or other excipients (e.g. antioxidants) to enhance stability.
▪ Liquid preparations (fluid extracts, tinctures) have advantages as to dose flexibility but an
unacceptable taste can be a problem in clinical practice.
▪ Oral powders are “preparations consisting of solid, loose, dry particles of varying degrees of
fineness. They contain one or more active substances, with or without excipients and, if
necessary, colouring matter (...) and flavouring substances. They are generally administered in
or with water or another suitable liquid. They are presented as single-dose or multidose
preparations”
▪ Capsules are solid preparations with hard or soft shells of various shapes and sizes, which
contain a single dose of one or more active substances, with or without excipients
▪ Cachets consist of a hard shell containing a single dose of one or more active substances with
excipients. The cachet shell is made of unleavened bread usually from rice flour and consists of
two prefabricated flat cylindrical sections.
▪ Tablets are defined in the Ph. Eur. as “solid preparations each containing a single dose of one or
more active substances”. Tablets are prepared by compressing uniform volumes of particles or
by another suitable manufacturing technique, such as extrusion, moulding or freeze-drying
(lyophilisation).
▪ Modified-release tablets are defined in the Ph. Eur. as preparations with a modified drug release
rate, place, or time at which the active substance is released compared to standard tablet
▪ Active substances are only absorbed from the gastro-intestinal tract in the dissolved state
▪ Dissolution of the active substance should occur as fast as possible after administration if an
immediate effect is intended.
- When an active substance is administered as a capsule or tablet, it will not be
immediately in contact with the surrounding fluid. Thus, rapid dissolution of an
active substance from a capsule or tablet requires the rapid disintegration of the
dosage form.
- The disintegration rate depends on the quantity and type of excipients and the
processing conditions, as well as on the active substance itself, particularly when
present in high fractions. Hydrophilic excipients improve the penetration of water
into the powder bed, hence the wetting of the preparation.
▪ Capsules release their contents when at least a part of the capsule shell is dissolved
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