Tutorial: Bioavailibility Flashcards
What is pharmacology?
It it the science of chemicals that potentially could benefit patietns
What is the difference between a drug and a medicine?
A drug is the chemical which should have its effect
A medicine is a dosage form of the drug but also contains excipients (zusätze)
What is the functio of exipents in a medicine?
- to improve its chemical and biological stability
- to increase its acceptability to the patient by improving its flavour, fragrance or appearance
- To make it able to grab e.g. the pill (increase size)
- to increase its bioavilibility
What involves the process called formulation?
The process of making a medicine (with excipients) containing a drug
What are the advantages and disadvantages of oral administration of a medicine?
Advantage
- It permits self-medication
- It does not require rigorously sterile preparations
- The incidence of anaphylactic shock is lower (than intravenous)
- There is the capacity to prevent complete absorption (vomiting, lavage).
Disadvantage
It is inappropriate for drugs which:
- are labile in acid pH of stomach or otherwise degraded
- or undergo extensive ‘first-pass’ metabolism,
It requires patient compliance.
What are the advantages and disadvantages of IV administration of drugs?
Advantage
- rapid onset of action
- avoids poor absorption from, and destruction within, the g.i. tract permits careful control of blood levels
Disadvantages
- slow injection necessary (to avoid toxic bolus) higher incidence of anaphylactic shock
- trained personnel required
- complications possible; embolism, phlebitis, pai
What are the advantages and disadvantages of inhalation/ administration of a drug via the lungs?
Advantages
- ideal for small molecules, particles, gases, volatile liquids, aerosols
- enormous surface area presented by alveolar membranes
- simple diffusion, also phagocytic cells clear particles
Disadvantages
- possible localised effect within lung (unless this is desired)
What are the advantages and disadvanatages of IM administration of a drug?
Advantages
- relatively high blood flow, increased during exercise enables DEPOT THERAPY (prolonged absorption from pellet, microcrystalline suspension or solution in oily vehicle).
Disadvantages
- possible infection and nerve damage (especially in gluteal region)
What are the advantages and disadvantages of a subcutaneous administratio of a drug?
Advantages
- Local administration, dissemination can be minimised for local effect
- enables DEPOT THERAPY (as for intramuscular above)
Disadvantages
- pain, abscess, tissue necrosis
What are the advantages and disadvantages of percutaneous (across the skin) administration of a drug?
Advantages
- local application and action
- lipid soluble compounds diffuse rapidly (may be assisted by vehicles)
Disadvantages
- local irritation and skin reactions
- alteration of skin structure (e.g. steroids – subcutaneous adipose tissue)
What is bioavailibility?
The amount of a drug contained in a medicine that enters the systemic circulation in an unchanged form after administration of the product
How do each of the following influene bioavailibitly of a drug?
- the physicochemical characteristics of the drug (ionisation in gut)
- gastrointestinal pH
- whether or not the drug is passively or actively transported
- gastrointestinal motility
- particle size of the drug
- physicochemical interaction between drug and gut contents (e.g. chemical interaction between calcium and tetracycline antibiotics)
- the physicochemical characteristics of the drug (ionisation in gut)
- gastrointestinal pH
–> diffusion of ver membrane
- whether or not the drug is passively or actively transported
–> might rely on transport mechanisms (can be genetically different)
- gastrointestinal motility
- particle size of the drug
–> Smaller Particle, higher motility= more/faster absorbtion
physicochemical interaction between drug and gut contents (e.g. chemical interaction between calcium and tetracycline antibiotics)
Does the measurement of bioavailability always reflect the effectiveness of a drug?
No, some durgs can be effective without having a high bioavailability
Also, some drugs have to be metabolised to be effective –> would potentially have low bioavilibilty (because of its definition)
What is the therapeutic index/therapeutic window?
The range of mount of drug that can be administered between
- Lower end: its usefullness
- Upper end: its toxicity
Name examples of how a drug can be altered in the presystemic metabolism/ first pass metabolism)
- the microbes within the gut lumen
- enzymes present in the gut wall
- enzymes in the liver
