Properties of Polymers
Polymers in pharmaceutical formulations, especially in Novel Drug Delivery Systems (NDDS), possess a wide range of properties that influence their applicability:
1. Molecular Weight:
Determines the mechanical strength and drug release profile.
High molecular weight polymers usually result in stronger films or matrices with slower drug release.
2. Solubility:
Polymers can be soluble or insoluble in water and other solvents.
This property is crucial when designing drug release profiles.
3. Biodegradability:
Some polymers degrade when exposed to physiological conditions, releasing the drug in a controlled manner.
4. Biocompatibility:
Essential for any material that is to be introduced into the body.
The polymer should not induce any inflammatory or immunological response.
5. Swelling Characteristics:
In hydrogel systems, the degree and rate of polymer swelling can control the drug release.
6. Thermal Stability:
For processes like tablet coating or hot-melt extrusion, polymers need to be thermally stable.
7. Viscosity:
The polymer's solution viscosity can influence the drug release and processability of the formulation.
8. Mechanical Properties:
The flexibility, tensile strength, and elasticity determine the polymer's suitability for various dosage forms.
Advantages of Polymers
1. Versatility:
Polymers can be tailored to provide a desired drug release profile, be it immediate-release, sustained-release, or delayed-release.
2. Improved Patient Compliance:
By allowing for controlled and sustained drug release, the frequency of dosage can be reduced.
3. Targeted Delivery:
Certain polymers can be designed to target specific sites within the body, thereby improving drug efficacy and reducing side effects.
4. Protection of Labile Drugs:
Polymers can offer protection to drugs that are sensitive to environmental factors like pH or enzymes.
5. Enhanced Bioavailability:
Controlled release systems can sometimes enhance the bioavailability of drugs that have a short half-life or are poorly soluble.
6. Stability:
Polymers can provide a stable environment for encapsulated drugs, thereby extending shelf life.
7. Flexibility in Formulation:
Polymers can be used in a variety of dosage forms, from tablets and capsules to injectables and transdermal patches.
Application of Polymers in Formulation of Controlled Release Drug Delivery Systems
1. Tablets and Capsules:
Polymers like hydroxypropyl methylcellulose (HPMC) and ethyl cellulose can be used to formulate controlled release tablets or capsules.
2. Hydrogels:
Superabsorbent polymers swell in the presence of water, releasing the drug in a controlled manner.
3. Transdermal Patches:
Polymers help in the formulation of adhesive layers that can release drugs over an extended period when applied to the skin.
4. Microspheres and Nanospheres:
Biodegradable polymers like polylactic acid (PLA) or poly(lactic-co-glycolic acid) (PLGA) can encapsulate drugs and release them in a controlled manner.
5. Liposomes:
While not strictly polymers, they often incorporate polymers to stabilize or modify the drug release.
6. Implants:
Biodegradable polymer implants can provide long-term, localized drug delivery.
7. Colon Targeted Delivery:
Using polymers that degrade specifically in the colonic environment, drugs can be targeted to the colon.
8. Mucoadhesive Systems:
Polymers can adhere to mucosal surfaces, enabling prolonged drug release at these sites.
9. In situ Gelling Systems:
Polymers that undergo a sol-gel transition based on specific triggers (like pH or temperature) can be used for controlled drug delivery.
