Introduction to Pharmacokinetics Flashcards
Enteral routes of administration
- Oral
- Rectal
Parental routes of administration
- Subcutaneous
- Intra-muscular
- Intravenous
- Intra-arterial
- Intrathecal
- Intraperitoneal
Percutaneous routes of administration
- Inhalation
- Sublingual
- Topical/transdermal
- Through mucus membrane
What is bioavailability?
Fraction of total dose of a drug that reaches the plasma
What does absorption depend on?
- Route of administration
- Blood flow at site of administration
- Dose of drug
- Active vs passive diffusion through membrane
- Drug solubility
- Bioavailability
What routes can drugs passively diffuse through?
- Through cells
- Through intracellular pores in some blood vessels
What does drug distribution depend on?
- Blood flow
- Lipid solubility of the drug
- Tissue binding
- Plasma protein binding
What is the apparent volume of distribution (AVD)?
The volume of liquid required to dilute the absorbed dose to the concentration found in plasma
What is the idea of ion trapping?
- Only unionised form of drug can cross membrane
- pH on other side of membrane favours ionised side of equilibrium
- Ions are formed on other side of membrane and can’t cross back
Where are weakly acidic drugs likely to accumulate?
Basic environments
What is first pass metabolism?
Metabolism of a drug before it reaches systemic circulation
What are the 2 biotransformations in metabolism?
- Phase I = oxidation via cytochrome p450 enzymes
- Phase II = conjugation reactions
What groups are added in phase I and what is the effect?
- Hydroxyl groups
- Compound gets more hydrophilic
What groups are added in phase II and what is the effect?
- Sulphates, glucuronidates, etc.
- Compound gets more hydrophilic
What drugs are activated instead of inactivated by metabolism (and how)?
Prodrugs (their metabolite(s) have more effect than the original drug)
