depot injections Flashcards
benefits of long acting preparations
- maintain constant drug release
- less frequent administration
- more convenience
- enhance compliance
- local and/or systemic treatment
types of long acting preparations
- oily solution/suspension
- aqueous suspension and lipid emulsion
- rate controlling membrane
- bioerodable microsphere, microcapsule, implant
- in situ forming system
- liposomes, lipid based liquid crystal
- nanoparticles and PEGylated nanocarriers
- modified drug analogue
2 types of rate controlling membranes
- polymeric based membrane system
2. osmotic based membrane system
drugs used in oily solutions
contraceptives
hormones
antipsychotic agents
vehicles used in oily solutions
vegetable oils - castor oils
synthetic FA esters - isopropyl myristate, ethyl oleate
problems with using vegetable oils as vehicles for oily solutions
prone to heat and light oxidation
conisderations for oily solutions
vehicle viscosity
drug solubility
drug partition between oil and aqueous media
What effects the drug solubility?
- degree of drug loading
- vehicles with low dielectric constant (lipophilic drugs dissolve in these)
- lipophilic drugs have high partition coefficient (P) and distribution coefficient (D)
melting point vs solubility in oil
higher melting point means lower solubility in oil
drug solubility after addding a co-solvent
solubility enhanced with addition of a co-solvent
What is the best co-solvent to add?
water immiscible solvent
What QC tests should be done?
- patriculate contamination
- sterility and bacterial endotoxins with test for pyrogen
- uniformity of dosage form and content
- in vitro release profiles
Why use small particles?
to avoid rapid sedimentation
Why use lower interfacial area and tension for small particles?
to avoid clumps and caking
What can temperature variation cause?
change crystal habit and size
What can concentrated suspension and irregular shape powder cause?
pain and irritation
What does thixotropic flow allow for?
consistent dispensing/dosing
What can water miscible organic solvent cause?
change solubility and can cause irritation
What deflocculation should be suspension be?
patrially deflocculated
What polymer is used in RCM (rate controll membrane) based implant?
polyethylene vinyl acetate
What does a higher vinyl acetate content in RCM based implant lead to?
lower Tg of polymer
glass transitional temperature
What is drug release based on in RCM based implant?
- SA of implant
- drug solubility in polymer
- concentration gradient
- membrane thickness
What is D (distribution coefficient)?
solubility of the drug in the oily phase
high D - high drug solubility in oily phase
better parittioning of drug into oily phase rather then aqueous phase
inc D - inc oil solubility
