solutions Flashcards
Name at least 3 liquid dosage forms
draught elixir linctus mixture mouthwash gargle inhalation spray nasal drops enema vaginal douche eye lotion eye drops injection infusion
Advantages of a solution as an oral dosage form
no need to dissolve the drug in the system
easier to swallow
disadvantages of a solution as an oral dosage form
taste
bulky
What is cosolvency
solubility of a weak electrolyte or non-polar compound in water can be improved by the addition of a water miscible solvent in which the compound is also soluble
The solubility of a drug is generally affected by…
the dielectric constant of the solvent system
ideally, suitable blends of solvents should have a dielectric constant between ____ and _____
25 and 80
What is solubilisation
the solubility of a drug in water can be improved by the addition of a surfactant
what is micellar solubilisation
the concentration of surfactant used should be above its critical micellar concentration
hydrophilic surfactants with HLB values above ___ are useful solubilising agents
15
Name 3 factors that affect the choice of solubilising agent
toxicity and nrrtancy
miscibility with solvent system
compatibility with other components
odour and taste
how do you determine the minimum concentration of surfactant for solubilisiation of drug
- series of vials with constant conc of surfactant is prepared
- diff amounts of the drug is added and the optical density of the mixtures determined
- maximum drug conc obtained
What is complexation
interaction of a poorly soluble drug with a soluble material to form a soluble complex
should complex formed be easily reversible?
yes
What is chemical modification
synthesis of soluble salts of the drug
What happens to a chemically modified drug in the body?
gets converted to the active base in the biological system
how is particle size reduced
milling
when is non-aqueous solvents used
prepare solution so drugs which are unstable in water
prepare IM injections of drugs for depot therapy
What are non-aqueous solvents classified into?
fixed oils of veg origins, alcohols, polyhedric alcohols, mineral oils and others
What types of formulations are fixed oils of vegetable origin used in
injections, eyedrops, liniments and oral prep
What is fractionated coconut oil used for
solvent for phenoxymethylpenicillin
tasteless and odourless fixed oils are used for…
oral prep
Types of alcohol
ethanol, industrial methylated spirit, isopropanol, polyhydric alcohols (glycerol, propylene glycol, PG, dipropylene glycol, dietyhlene glycol, ethylene glycol)
Ethanol is suitable for __________ use
internal and external
What conditions is ethanol most commonly employed in?
low conc, as a cosolvent with water in the formulation of aqueous solutions for oral and parenteral use
