Flashcards in Methods of formulation Deck (74):
To be classified as a colloid, the particles must not settle under gravity. True or false?
What is a sol?
A colloid suspension of solid particles in a liquid
An emulsion is a mixture of two solids. True or false?
False - two liquids
How is a foam formed?
When many gas particles are trapped in a liquid or solid
An aerosol contains small particles of liquid or solid dispersed in a gas, True or false?
What is meant by a lyophobic colloid?
What is meant by a lyophilic colloid?
Lyophilic sols exhibit low viscosity. True or false?
False - high viscosity
Are the particles in a lyophilic sol symmetrical or assymetrical?
Lyophilic particles are stable to addition of electrolytes. True or false?
Lyophobic sols exhibit high viscosity. True or false?
False - low viscosity
Lyophobic sols contain symmetrical particles. True or false?
Lyophobic sols are sensitive to the addition of electrolytes. True or false?
How are lyophobic dispersion systems formed?
The dispersion of oil in water
What is meant by dispersion?
The breakdown of coarse material by colloid mills or ultrasonic treatment
Condensation involves the slow production of a supersaturated solution of the colloidal material under conditions that cause formation of colloidal particles and not a precipitate. True or false?
False - the fast production
What are random zig zag collisions a result of?
Brownian motion - colloidal particles are able to spontaneously move from high conc to low conc
At what size will particles sediment under gravity?
0.5 micrometres or more
Particles less than 0.5 micrometres have to be sedimented by centrifugation. True or false?
Aggregates with an open structure are called ______
The majority of gels are formed by aggregation of colloidal sol particles. True or false?
What is a gel containing no liquid called?
Bentonite is a clay. What are clays composed of and how do they turn into gels?
Composed of charged particles and form gels by flocculation
Which type of bonds hold type 1 gels together?
Which type of bonds hold type 2 gels together?
Weak bonds e.g. hydrogen bonds
Type 1 gels are heat reversible. True or false?
False - they are irreversible
Type 1 gels swell in water and dissolve. True or false?
False - do not dissolve due to stabilising links
Type 2 gels are heat reversible. What is meant by this?
On heating or cooling there is a transition from sol to gel and vise versa
As temperature is increased, the solubility of type 2 gels increases. True or false?
False - decreases
Why does the solubility of type 2 gels decrease as temperature is increased?
Because type 2 gels form micelles and upon warming, more and more micelles form. The micelles are formed so closely together that movement is prevented and a gel phase is formed
A surfactant is an amphipathic molecule. What is meant by this?
It contains both hydrophilic groups and hydrophobic
CMC decreases as length of hydrocarbon chain increases. True or false?
How can the stability of an emulsion be increased?
Reduce globlet size
Decrease density difference
Increase viscosity of continuous phase
What particle size is needed for good penetration into the airways?
Aerosol particles above 20 micrometres are deposited in the mouth and throat. True or false?
False - more than 10 micrometres
What happens if the aerosol particles are less than 0.5 micrometres?
They may be exhaled
What is a foam?
A dispersion of a gas in a liquid
Surfactants are required for the formation of foams and emulsions. True or false?
What are the two ways in which an aerosol can be prepared?
What is the fate of aerosol particles that are 1-5nm in diameter?
They are exhaled
Drugs for treatment of erectile dysfunction can be taken through nasal delivery formulations. True or false?
How long is the nasal cavity?
In the nasal cavity, cilia of the nasal vestibule filter out particles of which diameter?
over 10 micrometres
What is the main drug absorption site in the nasal cavity?
The epithelium of the nasal turbinates
Particles of which diameter are deposited in the nasal cavity?
What is PecFent and what is it used for?
A nasal spray with the API fentanyl - used for breakthrough pain in people already receiving opioids on a regular basis
All drugs which are orally administered can be given rectally. True or false?
True - but may not be as effective
What are some disadvantages of rectal delivery systems?
Not favoured by patients
Development of proctitis
Slow and sometimes incomplete absorption of drug
Problems with insertion
Are there villi present on the rectum?
No - it has a flat surface with no villi
The rectum wall is composed of multiple layers of epithelium. True or false?
False - single layer of epithelium, composed of cylindrical cells and goblet cells that secrete mucous
What is the pH of the rectum in adults?
pH 7.5 and is slightly more alkaline in children
How many veins serve the rectum and what are they called?
Inferior, middle and superior haemorrhoidal veins
Where do the inferior and middle haemorrhoidal veins drain?
Into the inferior vena cava
Where does the superior haemorrhoidal vein drain?
hepatic portal vein
How does drug absorption take place in the rectum?
By passive diffusion
Why is bioavailability in the rectum unpredictable?
Because of inter-individual variations and due to venous drainage
Why is rate and extent of drug absorption via the rectum not as good as oral?
low fluid volume - effects dissolution of drug
There is a lot of fluid present in the rectum. True or false?
False - approx 3mls of mucous only
Water-soluble bases (suppositories) are mostly used for laxative purposes. True or false?
False - glycerinated gelatin bases are used (water soluble bases are used much less frequently)
Which type of suppository bases have a melting point above body temp?
To prevent sedimentation during manufacture what should the drug particle size of suppositories be?
less than 150 micrometres
Drug particles (suppositories) less than ___ micrometres will not cause irritation to the patient
What are the 3 ways in which suppositories are formed?
Inclusion of viscosity enhancers in suppositories slows down drug release. True or false?
What is the ideal weight of a suppository?
What are rectal capsules used for?
Systemic drug delivery - usually filled with a solution or suspension of drug
Why aren't rectal tablets not an ideal dosage form?
Due to the lack of water in the rectum - limiting dissolution
Rectal tablets that release CO2 after insertion stimulate what?
Defecation - discharge of faeces from the body
Progesterone administered orally has a higher bioavailability than that administered vaginally. True or false?
How long is the vagina?
What is the pH of the vagina in a healthy adult woman?
Why is the vagina weakly acidic?
Due to the conversion of glycogen to lactic acid by lactobacillus
What base should be used to make pessaries?