Principles of drug action Flashcards
What are the properties of the ideal drug?
Fast onset
Selectivity to the desired site
Low cost
No side effects
No interactions with other drugs
Good efficacy for desired length of time
Chemical stability
Safe and predictable
Easy to administer
Reversible action
What does chemical stability mean?
Effectiveness remains the same while in storage (not lost while stored)
What can make a drug easier to administer?
Low dose no (don’t have to take often)
Easy to take
Difficult to make mistakes while taking
What is the E50% on a dose response curve?
A measure of the effectivity of the half dose
A lower Kd (equilibrium constant) means…
There is a higher affinity (ligand is bound for longer)
What is potency?
How much of a drug is needed to produce the desired effect (i.e. higher potency needs less of the drug)
What is affinity?
Ability to bind to receptors easily (whether they will stay bound for a short or long time)
What is efficacy?
The drug’s ability to make changes once bound
Cholinergic neurons bind to…
Acetylcholine (ACh)
The types of cholinergic neurons are…
Nicotinic
Muscarinic
Adrenergic neurons bind to…
Norepinephrine (NE) AKA noradrenaline
Selectivity is…
A drug’s ability to bind to specific receptors and produce a desired effect
What should be considered when deciding the route of administration?
Site of action
Duration of action
Stability of drug (shelf life outside of the body)
What are the steps of instilling eye drops?
- Wash and dry hands
- Check expiry date, packaging in tact and that drug matches packaging
- Note drug type, %, expiry date, LOT number and time instilled on px record
- Advise px on what to do once drop in (blink gently, keep eyes closed and occlude punta)
- Px to look up and rest head back
- Instill one drop into lower fornix
- Px to close eyes and occlude inner puncta
Why is only a small amount of a drug instilled via drops delivered past the cornea?
Due to trans-corneal diffusion - the drug must maintain its equal balance of charge as it travels through the cornea. At different points in the cornea it must be either charged or uncharged and each time it leaves some behind.
