Emulsion dosage forms Flashcards
examples
Emulsion
- Topical creams
- total parental nutrition
Definition
Emulsion
- Cloudy or milky, the droplet size are polydispersed
- low conc of surfactant
- Thermodynamically unstable
Emulsion types
- O/W Normal emulsion lipophilic drugs
- Reverse emulsion W/O Suncream
- Multiple emulsion w/o/w Vancomycin hydrochloride
O/W watery creams
- Water is the continuous medium, while oil is the dispersed, o/w creams do not feel greasy
- Readily diluted and miscible with water; easily rinsed off
- Conduct electricity
- Can deposit lipids so restore skin hydration, however they are non-occlusive (block pores)
W/O Oily creams
- oil is the continuous phase
- More moisturising as they provide an oily barrier which reduces water loss
- Miscible with oil therefore not easily washable, however more easily spreadable
- Do not conduct electricity
O/W
Cream structure
1) Dispersed oil phase
2) Bulk water phase
3) Crystalline gel phase containing interlamellar fixed
water
4) Phase composed of crystalline
hydrates of cetostearyl alcohol
Creams
- Semi-solid creams require excess surfactant/co-surfactant compared required for stabilising runny emulsions
Cream structure
- Preservates are bound to the bilayer and bicelle
Creams
Less greasy but generally more acceptable than ointments
Lotions
Oil in the water so it is easily spreadable and can be used for mild dry skin
when shouldn’t you use an Ointment?
should not be used where an infection is present
Dye solubility test
Mix emulsion with a water-soluble dye (amaranth) and observed under the microscope
- Continuous phase appears red → o/w type
- Scattered globules appear red → w/o type
Dilution of emulsions
If the emulsion is o/w type
- Diluted with water → remain stable as water is the dispersion medium
- Diluted with oil → the emulsion will break
Conductivity
Based on the electrical conductivity of aqueous solutions, the electric current is supplied through electrodes placed in the emulsion
If the current is passed → o/w type
* Not passed → w/o type
Fluorescence
Based on the fluorescence of oils under ultraviolet light, examined under the light in the microscope
- Whole fluid is fluorescent → w/o type
* Spotty fluorescence → o/w type
