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[Meer zien]Voorbeeld 4 van de 54 pagina's
Voorbeeld 4 van de 54 pagina's
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VolgenVoorbeeld van de inhoud
Lecture 1Pharmacology = the study of the effects of drugs on living systems, aiming to improve their
functioning
Pharmacotherapy = refers to the treatment
of disease with drugs in an applied sense
Pharmacokinetics = what the body does to
a drug
Primary aim: To study and evaluate effects
of bio-active compounds in the diet with the
purpose of improving health and
preventing- or curing diseases.
Drug = a substance of known structure, other than a nutrient or an essential dietary
ingredient, which when administered to a living organism, produces a biological effect
→ Official (approved) indications may differ per registration
Formulation = refers to a combination of one or more active compounds (drugs) and one or
more excipients
Medicijn te gebruiken voor:
1) Het genezen, lenigen of voorkomen van enige aandoening, ziekte, ziekteverschijnsel,
pijn, verwonding of gebrek bij de mens
2) Het herstellen, verbeteren of wijzigen van het functioneren van organen bij de mens
3) Het stelen van een medische diagnose door toediening aan of aanwendig bij de mens
Medicines need approval by national authorities (CBG) or European authorities (EMA).
Each medicine allowed to be sold in NL should have a unique registration code:
➢ RVG code → nationally approved
➢ RVH code → homeopathic medicines
➢ EU code → European registration
Naproxen-sodium → nonsteroidal anti-inflammatory
drug (NSAID). Binds to cyclo-oxygenase; starts with
membrane phospholipids which contain fatty acids.
Arachidonic acid:
• COX I → gastro-protective prostaglandins
• COX II → inflammatory prostaglandins
LET OP! There’re structural differences between the substrate-binding channels of COX-1
and COX-2 that allowed the design of selective inhibitors → some substrates are
nonselective; can bind to both. Some substrates are only COX-2 selective inhibitors.
1
,There needs to be a certain balance
between the selectivity for COX
inhibition. To much blocking COX II?
Higher risk at cardiovascular diseases. To
much blocking COX I? Gastrointestinal
risk.
Dosage form
Drug substances are rarely administered alone, but as a part of a formulation or dosage
form. Formulation can have varied and specialized pharmaceutical functions.
Coated tablet → only releases at right spot; coating protects core in the stomach. Drug
released in the upper GI tract after the stomach.
In order to be absorbed, a
drug needs to be in dissolved
state.
Drugs needs to be transported
via the blood.
Drugs are being removed from
the bloodstream via
elimination and/or
biotransformation.
There are different processes phases in pharma:
1) Pharmaceutical phase → formulation, administration, des-integration, dissolution
2) Pharmacokinetic phase → absorption, distribution, metabolism, excretion (ADME)
3) Pharmacodynamic phase → interactions with molecular target
4) EFFECT
There also different routes of application:
Also processes determining oral
bioavailability.
Biotransformation occurs in the
liver.
2
,Basics of oral drug absorption
➢ Determined by the drug’s physicochemical properties, formulation, and route of
administration
➢ A drug must cross several semi permeable cell membranes before it reaches the
systemic circulation → cell membranes = biological barriers that selectively inhibit
passage of drug molecules
➢ Most of the absorption takes place in the duodenum
➢ The drug should be in dissolved state
➢ Often by passive diffusion → sometimes active transport involved
➢ Lipid soluble compounds (partly) with lipids
Drugs may cross by passive diffusion, facilitated passive diffusion, active transport, or
pinocytosis:
Passive diffusion = from high to low concentration (directly proportional to the gradient but
also depends on molecule’s lipid solubility, size, and degree of ionization → because cell
membrane is lipid, lipid-soluble drugs diffuse most rapidly
- Partition coefficient (P) = provides an indication for the distribution of
a compound over a lipophilic phase and water (octanol often used as
lipophilic state)
Most drugs are weak organic acids or bases, existing in un-ionized and ionized forms in an
aqueous environment.
- Un-ionized? Lipid soluble and diffuses readily across cell membranes
- Ionized? Lower lipid solubility (but more hydrophilic) and higher electrical resistance;
cannot penetrate cell membranes easily.
pKa is the concentration at which concentrations of ionized and un-ionized forms are equal:
pKa > pH → higher un-ionized form of weak acid & higher ionized
form of weak base
Facilitated passive diffusion = a carrier molecule in the membrane combines reversibly with
the substrate molecule outside the cell membrane → membrane transports only subtrates
with a relatively specific molecular configuration, and the availability of carries limits the
process
Active transport = requires energy expenditure, transport against a concentration gradient
Pinocytosis = fluid or particles are engulfed by a cell; the cell membrane invaginates,
encloses the fluid or particles, then fuses again, forming a vesicle that later detaches and
moves to the cell interior → energy expenditure is required
3
, A drug placed between the gums and cheek (buccal administration) or under the tongue
(sublingual administration) is retained longer, enhancing absorption. LET OP! Because most
absorption occurs in the small intestine, gastric emptying is often the rate-limiting step
(membranes in small intestine are more permeable than those in the stomach).
Because solid drug forms must
dissolve before absorption can
occur, the dissolution rate
determines availability of the
drug for absorption, and may
become the rate-limiting step if
slower than absorption →
manipulating the formulation can
change the dissolution rate and
thus control overall absorption.
Rate-limiting step = the slowest step in a metabolic pathway or series of chemical reactions,
which determines the overall rate of the other reactions in the pathway → LET OP!
Absorption can be rate-limiting.
→ Rate-limiting steps are determining ultimate effect!
→ Less rate limiting when tablet transformed to fine particles.
→ When it’s too polar, sometimes it’s not absorbed.
Excretion
The kidneys are the principle organs of excretion → contribution of intestine, saliva, sweat,
breast milk, and lungs to excretion is small. Exretion via the bile occurs: BUT: can be re-
absorbed by the entero-hepatic cycle.
Drugs bound to plasma proteins remain in the circulation; only unbound drug is contained in
the glomerular filtrate.
Acidification of urine increases reabsorption and decreases excretion of weak acids and
decreases reabsorption of weak bases.
Some drugs and their metabolites are extensively excreted in bile. Because they are
transported across the biliary epithelium against a concentration gradient, active secretory
transport is required.
4
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