cv formulations Flashcards
Type of formulation depends on two factors:
Onset of action needed (e.g. Angina)
Nature of the disease (e.g. HT)
Delivery using the parenteral route
Drug is is directly introduced in the blood (readily available) Fast onset Bypass first pass metabolism Bolus or infusion (intravenous) Intramuscular Subcutaneous
Drug can be in the form of a solution (route will be specified according to condition
Delivery using the sublingual route (under the tongue)
Thin mucosa of the sublingual region
Rich blood supply
Fast onset of action
However, not suitable for all drugs
Drug should be potent (active at low dose)
Water soluble
Relatively small MW- it can cross readily
formulation and absorption of GTN?
Rapidly absorbed from GIT but…
Subject to extensive first pass metabolism
GTN= glyceryl trinitrate
Half life spray 3.5min and tablet
*check how to do halflife
300 mcg sublingual tablets
Stabilised by presence of absorbent mannitol and lactose
Storage
Glass bottle (GTN adsorbed by plastic)
Drug can evaporate from tablets (8 wk shelf life)
Close container, don’t transfer from container
Risk of loss of efficacy if above not followed
GTN spray
400 mcg metered dose
Spray under the tongue
Much longer shelf life (years)
Delivery using the transdermal route (Skin)
Sustained release of the drug Compliance and less erratic absorption Onset of action is not critical Depends on the type of the drug Water soluble Smaller drug (MW)----> cross stratum corneum towards epidermis and dermis
GTN transdermal (prophylaxis) (patches)
Prophylaxis of angina
‘5’ patch: releases 5 mg / day
’10’ patch: releases 10 mg / day
Use one per day, rotate site ofapplication
good shelf life (3 years)
Lateral chest wall, upper arm, thigh, abdomen, or shoulder
Tolerance: remove for 8-12 hours (overnight)
Check BNF!
GTN transdermal
patch structure
Patch structure
1) an impermeable tan-coloured backing film
2) a drug reservoir containing glyceryl trinitrate with lactose
3) a semi-permeable release membrane that controls the release of glyceryl trinitrate to the skin
4) a layer of silicone adhesive
5) a white to off-white coloured protective liner which is removed prior to use
Delivery using the oral route
Reserved for chronic stable conditions
Same absorption conditions (pH, Log P, surface area of SI)
Onset of action is not critical
Opportunity to modify the drug release
Controlling release
why polymeric film coating
Limit access of the environment to the API
Limit access of the API to the environment
Polymeric film coating
e. g. enteric coating to protect API from stomach acid (e.g. Eudragit)
e. g. membrane that controls rate of diffusion out of core
what does Matrix based mean
Control rate of access of the environment to the API
Matrix is a solid with pores containing the API
e. g. hydrophillic
e. g. hydrophobic, non soluble
e.g. Slow-K modified release K+Cl- (used to replace K+ lost through the use of diuretics)Salt is embedded in a wax matrix and leeches out slowly
why cant tablets be crushed?
if you do crush, risk of ‘dose dumping’
drug is released much fast than intended, with serious consequences
examples of beta blockers
- propanol
- atenolol
