Oral (Solutions) Flashcards
Advantages of oral solutions: (3)
fast onset of action
dose uniformity
easy to swallow and easy to manufacture
Disadvantages of oral solutions: (3)
increased drug instability compared to in solid state
packaging costs higher
many drugs are poorly soluble in water
Oral solutions must be… (4)
stable
palatable
appropriate viscosity
at physiological pH
Most common solvent is water, why?
lack of toxicity
low cost
purified water is used - produced by distillation
What can be added to drugs to make them more water soluble?
co-solvents e.g. ethanol, glycerol
Excipients in solutions: (5)
antioxidants
flavouring, colouring agents
preservatives
viscosity enhancers
sweeteners
Factors effecting chemical degradation: (4)
high temp
pH
UV light
catalyst
How to enhance solution stability? (3)
package in containers that reduce light transmission
formulate at suitable pH
include excipients
How does pH affect solubility?
Ions are more water soluble than neutral molecules
alter pH can increase drug ionisation which increases drug solubility
Weakly acidic drugs are ionised when…
solvent pH increases
Lower solvent pH increases ionisation of…
weakly basic drugs
When are co-solvents used?
For non-ionic drugs where solubility cannot be adjusted by pH control
like dissolves like when choosing them
What are Cyclodextrins?
sugar molecules bound together in a ring
interior cavity - hydrophobic
exterior - hydrophillic
drug is releases from them and the free drug is absorbed increases aqueous solubility of drug
