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1. The diffusion coefficient of tetracycline in a hydroxyethyl
methacrylatemethyl methacrylate copolymer
film in a mole ratio of 2:98 isD=8.0 (±4.7)∗ ×10−9
cm2/sec and the partition coefficient, K, for tetracycline
between the membrane and the reservoir is 6.8
(±5.9) × 10−3. The membrane thickness, h, of the
trilaminar device is 1.40 × 10−2 cm, and the concentration
of tetracycline in the core, Co, is 0.02 g/cm3
of the core material. Using equation (11103), calculate
the release rate, Q/t, in units of μg cm−2 of
tetracycline per day
2. The release of ethynodiol diacetate through a silicone
dosage form may be calculated using the Higuchi
equation,
Q/t1/2 = [D(2 A − Cs)Cs]1/2 (3)
because diffusion is found in this case to be the ratelimiting
factor for drug release. A, the amount of drug
per unit volume of the silicone matrix, is 100 g/(103
cm3); the solubility, Cs, of the drug in the silicone
polymer is 1.50 g/(103 cm3); and D, the diffusivity of
the drug in the silicone matrix, is 3.4×10−2 cm2/day.
Calculate the rate of drug release from the silicone
dosage form in units of g/(103 cm2) per day1/2
3. A new drug is placed in a Graham closed-boundary
diffusion cell (see Fig. 1127) to determine the drugs
diffusion coefficient, D. The initial concentration of
the drug, u0, is 0.0273 g/cm3 in water at 25◦C. The
total height of the cell isH=3.86 cm and the height of
the drug solution in the cell is h = 1.93 cm. A sample
is taken at a depth of x = H/6 at time t = 10,523 sec
(2.923 hr) and analyzed for the drug; its concentration,
u, is found to be 0.0173 g/cm3. Rearrange equation
(11108) so as to calculate D, the drugs diffusion
coefficient.
methacrylatemethyl methacrylate copolymer
film in a mole ratio of 2:98 isD=8.0 (±4.7)∗ ×10−9
cm2/sec and the partition coefficient, K, for tetracycline
between the membrane and the reservoir is 6.8
(±5.9) × 10−3. The membrane thickness, h, of the
trilaminar device is 1.40 × 10−2 cm, and the concentration
of tetracycline in the core, Co, is 0.02 g/cm3
of the core material. Using equation (11103), calculate
the release rate, Q/t, in units of μg cm−2 of
tetracycline per day
2. The release of ethynodiol diacetate through a silicone
dosage form may be calculated using the Higuchi
equation,
Q/t1/2 = [D(2 A − Cs)Cs]1/2 (3)
because diffusion is found in this case to be the ratelimiting
factor for drug release. A, the amount of drug
per unit volume of the silicone matrix, is 100 g/(103
cm3); the solubility, Cs, of the drug in the silicone
polymer is 1.50 g/(103 cm3); and D, the diffusivity of
the drug in the silicone matrix, is 3.4×10−2 cm2/day.
Calculate the rate of drug release from the silicone
dosage form in units of g/(103 cm2) per day1/2
3. A new drug is placed in a Graham closed-boundary
diffusion cell (see Fig. 1127) to determine the drugs
diffusion coefficient, D. The initial concentration of
the drug, u0, is 0.0273 g/cm3 in water at 25◦C. The
total height of the cell isH=3.86 cm and the height of
the drug solution in the cell is h = 1.93 cm. A sample
is taken at a depth of x = H/6 at time t = 10,523 sec
(2.923 hr) and analyzed for the drug; its concentration,
u, is found to be 0.0173 g/cm3. Rearrange equation
(11108) so as to calculate D, the drugs diffusion
coefficient.
