Principles of Depot Injections + Formulations Flashcards
What are the advantages of long acting injectables?
Predictable drug release profile
Better patient compliance
Ease of application
Avoidance of 1st pass
Reduced dosing
Decrease incidence of side effects
Cost reduction
What are the different route of applicable injection?
SC
IM
What’s good about SC?
Greater surface area
Shorter needles
Less discomfort
Better safety profile
What’s bad about SC?
Limited to no more than 1-2ml
What is SC the primary route for?
Protein-based drugs
What’s good about IM?
Greater injection vol
What are the types of long acting injectable formulations?
Oil-based solutions
Drug suspension
Polymer-based
What are oil-based solutions suitable for?
Steroid esters
eg. contraception, hormone replacement therapy + antipsychotics
What is the route of injection for oil-based solutions?
IM
What is the important formulation consideration of oil-based solutions?
Drug solubility
Drug partitioning
Vehicle viscosity
What are the properties of oil vehicles?
Vegetable oil
Synthetic fatty acid esters
Castor oil
What is the partition coefficient?
Ratio of drug activities in 2 immiscible solvents comprising the partitioning system
What is the rate-limiting step of drug absorption in drug suspensions?
Dissolution of drug particles
What are poorly water-soluble salt formations used for in drug suspensions?
Control dissolution rate of drug particles to prolong the absorption
What are polymer-based systems suitable for?
Macromolecules - eg. peptides, proteins
What are the advantages of polymer-based systems?
In vitro + in vivo stabilisation of macromolecules
Extension of biological half life
Improvement of systemic availability
What polymer properties play a role into drug release?
Composition of copolymer ratios
Hydrophilicity/hydrophobicity
Molecular mass
Glass transition temperature
What is an example of appropriate polymers?
Biodegradable microspheres
How does the release process of microspheres work?
From surface, through pores, diffusion through polymer barrier, diffusion through water-swollen barrier, polymer erosion + bulk degradation
What are in situ-forming gels?
Made of biodegradable products, injected into body then congeal to form solid implant
Describe how in situ-forming gels work
Drug-polymer solution injected in a suitable solvent system
Solvent diffuses out = water insoluble polymer solidifies + entraps drug
Drug slowly released from biodegradable depot
