What is a partial agonist?
Agonist cannot enact 100% response. When in solution with an agonist can act as a competitive antagonist
What is drug Specificity and drug selectivity?
Specificity - Targets only one subtype of a receptor e.g. beta2
Selectivity - Targets all types of a particular receptor e.g. beta receptors
What is affinity?
Tendency of a drug to bind to a specific receptor type
What is efficacy?
Ability of a drug to produce a response as a result of receptor being occupied
What is potency?
Dose required to produce the desired biologic response
How do you calculate the therapeutic index of a drug?
EC50 (adverse effect) / EC50 (desired effect)
How do you calculate the Vd?
Vd = Dose/[Drug]t0
What effect does grapefruit juice have on enzymes?
Inhibits several CYP450 isoenzymes
What effect does cranberry juice have on enzymes?
inhibits CYP2C9 isoform enzyme
How can liver failure impact on drug clearance?
Increased half life, less enzymes
How can cardiac disease impact drug clearance?
Reduced organ perfusion of liver and kidneys
How does renal failure impact drug clearance?
Less quickly eliminated through waste
How would you calculate the loading dose necessary for a drug?
Loading dose = Vd x [drug]target
What is the relationship between half life of drug and volume of distribution?
Higher volume of distribution = higher half life
How does the multi compartment model affect drug clearance?
Drug can be excreted from different compartments (muscle, fat, plasma) at different rates
What are the main routes of administration via the enteral route?
oral, rectal, sublingual
What are the primary parenteral routes?
intravenous, intra-arterial, intramuscular, intrathecal, subcutaneous
What are the pros and cons of enteral?
pros - cheaper, easier to use, can self administer
cons - drug can be metabolised, slower onset, irritates GI, unsuitable if vomiting (oral)
What are the pros and cons of parenteral?
Pros - quick onset, no degradation, dosing can be exact
Cons - must be sterile, requires HCPs, more expensive, unconvenient
What are the pros and cons of transdermal delivery?
Pros - steady rate of drug delivery, avoid breakdown by liver
Cons - Suitable only for lipid soluble drugs, relatively expensive
Some drugs work at a concentration in the plasma that approaches total saturation of the serum albumin. Why would increasing the dosage of such a drug have a disproportionate effect on the body?
Only the unbound molecules are active. Increasing drug conc when total saturation has reached would result in far more unbound molecules than in previous increases of drug conc
How does the blood flow through adipose tissue affect uptake of drugs into adipose?
Body fat has a low blood supply and therefore when drugs are administered acutely only very lipid soluble drugs will partition siginificantly into fat.
However, when a drug is administered chronically then levels of that drug can build up over time in the fat stores
What pH drug does albumin mainly bind?
What 2 factors concerning the drug itself determine the rate of drug absorption from the intestine?
Lipid solubility and ionisation
2 drugs that are expected to act in a very similar way