🔹 Pharmacokinetics Flashcards
(46 cards)
What is pharmacokinetics?
Pharmacokinetics is the study of the movement of a drug into and out of the body
“What the body does to the drug”
What is pharmacodynamics?
Pharmacodynamics is the study of drug effect and mechanisms of action
“What the drug does to the body”
What is pharmacogenetics?
Pharmacogenetics is the effect of genetic variability on the pharmaco- kinetics/dynamics of a drug on an individual
What are the two forms of drug administration?
- Enteral – delivery into internal environment of body (GI tract)
- Paraenteral – delivery via all other routes that are not the GI
What are the 9 different types of drug administration into the body?
- Oral
- Intravenous
- Intramuscular
- Transdermal
- Inhalation
- Subcutaneous
- Sublingual
- Intrathecal
- Rectal
Briefly, identify and describe the four main processes involved in drug therapy?
- Pharmaceutical process – “Is the drug getting into the patient?”
- Pharmacokinetic process – “Is the drug getting to its site of action?”
- Pharamcodynamic process – “Is the drug producing its required pharmacological effect?”
- Therapeutic process – “Is the pharmacological effect being translated into a therapeutic effect?”
What are the four processes involved in pharmacokinetics?
- Drug in:
I. Absorption
II. Distribution
- Drug out:
I. Metabolism
II. Excretion
What is bioavailability?
Bioavailability is the fraction of a dose which finds its way into a body compartment (usually the circulation)
How does one calculate oral bioavailability?
Oral Bioavailability (F) = AUCoral / AUCIV
What are the factors which affect bioavailability?
- Absorption – drug formulation, age, food, vomiting / malabsorption
- First pass metabolism
What is first pass metabolism?
First pass metabolism is any metabolism occurring before the drug enters the systemic circulation
Identify three common locations where first pass metabolism occurs
- The Gut Lumen
- The Gut Wall
- The Liver
What is drug distribution?
The distribution of a drug refers to its ability to ‘dissolve’ in the body
What are the two factors affecting drug distribution?
- Protein binding
- Volume of Distribution (Vd)
In three steps, explain how protein binding determines drug distribution
⇒ In systemic circulation, many drugs are bound to circulating proteins
⇒ Most drugs must be unbound to have a pharmacological effect
⇒ The free fraction of the drug can bind to cellular receptors, then gain access to cellular enzymes
Once in the systemic circulation, many drugs are bound to circulating proteins.
Provide four examples of this
- Albumin (acidic drugs)
- Globulins (hormones)
- Lipoproteins (basic drugs)
- Acid glycoproteins (basic drugs)
What happens when a drug is displaced from its binding site?
Displacement of drugs from binding sites causes protein binding drug interactions
Changes in protein binding can occur, causing changes in drug distribution. However, these are only important if 3 criteria are met.
What are these criteria?
- High protein binding
- Low Vd
- Has a narrow therapeutic ratio
Identify four factors which affect protein binding
- Hypoalbuminaemia
- Pregnancy
- Renal failure
- Displacement by other drugs
If a drug is not bound to plasma proteins, it is available for distribution to the tissues of the body.
How can one measure the tissue distribution of a drug?
Volume of distribution
What is volume of distribution?
Volume of distribution is a measure of how widely a drug is distributed in body tissues
How can one calculate volume of distribution?
Volume of distribution (Vd) = Dose / [Drug]t0
Identify six factors which might affect the tissue distribution of a drug
- Specific receptor sites in tissues
- Regional blood flow
- Lipid solubility
- Active transport
- Disease states
- Drug interactions
What are the end products of drug metabolism (usually)?
- After conjugation, water-soluble metabolites are formed
- Usually, they are pharmacologically inactive
