depot injections Flashcards
what are the benefits of long-acting preparation?
- Maintain constant drug release
- Less frequent administration
- More convenience
- Enhance compliance
- For local and/or systemic treatment
what is typical of long acting preparations?
• Oily solution/suspension
• Aqueous suspension and lipid emulsion
• Rate controlling membrane, e.g. Implanon, DUROS
– Polymeric based membrane system
– Osmotic based membrane system
• Bioerodible microsphere, microcapsule, implant
• In situ forming system
• Liposomes, lipid based liquid crystal
• Nanoparticulate and PEGylated nanocarriers
• Modified drug analogue etc.
what is the compoisition of an oily solution?
drugs + vehicles- e.g. veg oil/ caster
what are the features of veg oils? i.e. vehicles
– Various fatty acid compositions
– Acceptable chemical stability
– Prone to heat and light
what are the considerations for an oily solution?
- Vehicle viscosity
- Drug solubility
- Drug partition between oil and aqueous media (D)
how is drug solubility affected?
• Degree of drug loading
• Vehicle with low dielectric constant
• Drugs with lipophilic features have high partition
coefficient (P); distribution coefficient(D)
how does the drug solubility vary with cosolvent?
enchanced drug solubility with addition of co-solvent
preferably water immiscible solvent
what does the dissolution profile show?
drug partition between oil and awueous media
diffusion of drug from oil phase to water phase
rate of drug release
what considerations are there for aqueous suspensions?
• Drug properties
– Size, crystal habit, pKa, density, interaction propensity
• Vehicle properties
how does the vehcile properties affect aqueous suspension considerations?
– pH affects drug dissolution rate/stability/partition
– Viscosity affects sedimentation rate/drug diffusivity
– Wetting ability for dispersibility of drug
– Flocculating capability & redispersibility to promote
stability
what considerations are there for aw suspensions?
• Need small particles to avoid rapid sedimentation
• Need to lower interfacial area & tension for small
particles to avoid clumps & caking
• Lyophilic or lyophobic powder & degree of wettability
• Avoid temperature variation that may change crystal
habit & size
• Concentrated suspension & irregular shape powder can
cause pain & irritation
• Thixotropic flow allow for consistent dispensing/ dosing
• Partially deflocculated system
• Water miscible organic solvent changes solubility & can
cause irritation
what is the RCM based implant?
• Polyethylene vinyl acetate • Non degradable polymer • Drug permeability depends on vinyl acetate content • Higher vinyl acetate content, lower Tg of polymer • Co‐extrusion process
