Noyes-Whitney equation Dissolution rate dc/dt=Ks(Cs℃)K=D/8 K- dissolution rate constant S-surface area of undissolved solid D-diffusion constant of drug Cs- solubility in dissolution medium 0- Thickness of boundary layer C-concentration in medium V-Volume of dissolution medium
Noyes-Whitney equation Dissolution rate: dC/dt=KS (CS -C) K=D/Vδ K- dissolution rate constant S- surface area of undissolved solid D- diffusion constant of drug CS - solubility in dissolution medium δ- Thickness of boundary layer C- concentration in medium V- Volume of dissolution medium
Lactose(30-60p 1.2 Adm 10μ Intal a)Oral: oral Cromolyn Sodium(2-6u b)Inhalation c)Nasal d)Topical: large open wound e)Ear powder f) Preparing for further treatment: suspension. syrup, oral drops, injection
1.2 Administration routes a) Oral: oral powders, effervescent powders b) Inhalation: dry-powder as pulmonary DDS c) Nasal d) Topical: large open wound e) Ear powder f) Preparing for further treatment: suspension, syrup, oral drops, injection
1.3 Advantages and disadvantages a) Chemically stable and long shelf-life b) convenient for patients c)Orally powders fast dissolution d) Topical powders large spread area
1.3 Advantages and disadvantages a) Chemically stable and long shelf-life b) Convenient for patients c) Orally powders fast dissolution d) Topical powders large spread area
1.3 Advantages and a)Less convenient than tablets or capsules b) Hard to mask unpleasant taste c)Difficult to protect from atmospheric moisture or oxygen d)Not suitable for low dose(difficult measurement) e)Not suitable for drugs irritate or damage stomach
1.3 Advantages and disadvantages a) Less convenient than tablets or capsules b) Hard to mask unpleasant taste c) Difficult to protect from atmospheric moisture or oxygen d) Not suitable for low dose (difficult measurement) e) Not suitable for drugs irritate or damage stomach
Divided Powders Have generally fallen into disuse because of the ready availability of tablets and capsules Some commercial OTC products are packaged in similar unit-dose packets -BC Headache Powders -Stanback Analgesic Powders
Divided Powders • Have generally fallen into disuse because of the ready availability of tablets and capsules. • Some commercial OTC products are packaged in similar unit-dose packets: –BC Headache Powders –StanbackAnalgesic Powders