Approaches to design transdermal drug delivery system.

1. BY SAYEDA SALMA,
1ST M PHARM

2. INDEX
APPROCHES FOR DEVELOPING TDDS.
 Polymer membrane permeation controlled TDD system
 Polymer matrix diffusion controlled TDD system
 Drug reservoir gradient controlled TDD system
 Micro reservoir dissolution controlled TDD system

3. INTRODUCTION
• Several approaches have been successfully
developed to provide over the release and skin
permeation of drugs.
• These technologies can be classified in to four
basic approaches.

4. POLYMER MEMBRANE PARTITION –
CONTROLLED TDDS
 In this type of system, the drug is
sandwiched between a drug impermeable
backing laminate and rate controlling
polymeric membrane.

5. (DRUG RESERVOIR)
Drug grounded particle
Dispersed in solid suspended in viscous
polymer matrix. + liquid medium (silicon)
Rate controlling polymeric membrane (EVA).
Adhesive polymer (silicon)
Ex: 1) FDA approved Transderm - nitrogycerine for angina pectoris.
2)Transderm – scop for motion sickness

6. THE RATE OF DRUG RELEASE FROM THIS SYSTEM IS DEFINED BY :
dQ CR Km/r Ka/m Da Dm
dt Km/r Dm ha + Ka/m Da hm
CR = drug concentration in reservoir compartment
Km/r = partition coefficient for the interfacial partitioning of drug from reservoir to the membrane
Ka/m= the partition coefficient for the interfacial partitioning of drug from membrane to adhesive
Da= diffusion coefficient in rate controlling membrane
Dm = diffusion coefficient in adhesive layer
ha= thickness of rate controlling membrane
hm = thickness of adhesive layer

7. POLYMER MATRIX DIFFUSION –
CONTROLLED TDDS
• In this system, the reservoir is formed by
homogenously dispersing the drug solids
in a hydrophilic or lipophilic polymer
matrix.

8. • Drug reservoir: dispersing drug particles in a hydrophilic or lipophilic polymer matrix
accomplished by -
homogenously mixing of grounded drug particles
liquid highly viscous blending of drug solids
polymer base polymer with rubbery polymer
Moulded in medicated disc

9. Also prepared by dissolving drug and polymer in common solvent
(solvent evaporation method)
spread on occlusive base plate
fabricated on Impermeable plastic membrane

10. THE RATE OF DRUG RELEASE FROM THIS SYSTEM IS DEFINED BY :
dQ Ld Cp Dp 1/2
dt 2t
Ld = drug loading dose initially dispersed in polymer matrix
Cp= solubility of drug in polymer matrix
Dp = diffusivity of drug in polymer matrix
Ex: Nitro-Dur system and Nitroglycerine transdermal system for angina
pectoris.

11. DRUG RESERVOIR GRADIENT-
CONTROLLED TDDS
• Simple form of membrane permeation
controlled TDDS or adhesive dispersion
type TDDS.
• Involves multi-laminate adhesive layers.

12. (Drug reservoir)
drug particle
dispersed in multi-laminate adhesive polymer
(poly-isobutylene or poly-acrylate )
Medicated disc
(solvent casting or hot melt)
Impermeable metallic plastic backing
Ex: isosorbide dinitrate releasing TDDS for angina pectoris.

13. THE RATE OF DRUG RELEASE FROM THIS SYSTEM IS DEFINED BY :
dQ KFa/r Da
dt ha (t) ld (ha)
 ha (t) = thickness of diffusional path through which drug molecules diffuse
increases with time.
 Ld (ha)= drug loading level in the multilaminate adhesive layer is designed to
increase drug release proportionally.

14. MICRO-RESERVOIR DISSOLUTION-
CONTROLLED TDDS
Micro-sealed dissolution controlled TDDS.
It is considered as a combination of
reservoir and matrix diffusion type drug
delivery system.
Ex: nitrodisc system for angina pectoris.

15. (Drug reservoir)
solid drug particle
Aqueous solution
(water soluble liquid polymer)
Drug suspension
Dispersing in lipophilic polymer(silicon)
by high dispersion technique
Microscopic drug reservoir
(spheres of DR)
Surrounded by adhesive film