Solid dosage forms
Download 37.21 Kb.
|
- Navigate this page:
- 2. AS PHARMACEUTICAL DOSAGE FORMS DIVIDED POWDERS
- Example: Prepare divided powders containing 1mg of active ingredient each required to be taken 2 times a day for 5 days. Solution
| VERY-FINE POWDERS: All the particles should pass through a sieve with nominal mesh aparture of 125um but not more than 40% should pass through a sieve with nominal mesh aparture of 45um
MICRO-FINE POWDERS: Powders of not less than 90% should pass through a sieve with nominal mesh aparture of 10um SUPERFINE POWDERS: Not more than 90% of the number of particles are less than 10% 2. AS PHARMACEUTICAL DOSAGE FORMS DIVIDED POWDERS: These are powders used for potent drugs (low-dose drugs) i.e. drugs that are effective in low concentration e.g. Atropine. They are usually diluted with a diluent which is usually an inert substance. They are called divided powders because they are dispensed as different powders with each dose wrapped differently and dispensed i.e. each powder represents a single dose. Divided powder = Active ingredient + Diluent (e.g. lactose) mixed Wrapped separately Example: Prepare divided powders containing 1mg of active ingredient each required to be taken 2 times a day for 5 days. Solution: Given that; 1mg x 2/day x 5days = 2mg x days = 10mg (total) But the minimum weighable amount for class A dispensing balance is 50mg and the total amount now required is less than 50mg. Therefore weigh 50mg of active ingredient and add 450mg of lactose (diluent) hence diluting it in a ratio of 1:10 (recommended ratio) 50mg A.I. + 450mg Lactose = 500mgT1 Since 500mgT1 contains 50mg of A.I. .: xmg of T1 will contain 10mg of A.I. x = 500 x 10 50
:. 100mgT2 contains 10mg A.I. Since each powder represents a single dose of 1mg, therefore 10 powders should be prepard and each powder should weigh a total of 200mg. 10powders x 200mg = 2000mg But 100mgT2 contains 10mg A.I. :.Amount of diluent (lactose) to be added will be = 2000mg (lactose) – 100mg (T2) = 1900mg of lactose. :. Add 1900mg of lactose to 100mgT2 Now since 2000mg of total mixture contains 10mg of A.I. 200mg of each powder should contain xmg of A.I. x = 200 x 10 2000
Therefore, each powder weighing 200mg contains 1mg A.I. A.I. = Active Ingredient Now, using a digital balance, weigh 200mg each of the total mixture and wrap seperately and send as directed. N.B: In extemporaneous dispensing, when preparing a divided powder, a minimum of 2 excess powders are expected (must) to be prepared so that in the above example a total of 12 powders will be prepared but only 10 (as direced) should be sent. Download 37.21 Kb. Share with your friends:
|