Introduction to targeted drug delivery systems.

 

Introduction.

• The medication is distributed throughout the body by systemic blood circulation in traditional drug delivery systems such as oral ingestion or intravascular injection. 

• Most therapeutic agents only reach a small portion to the affected area, such as chemotherapy, where roughly 99% of the drugs administered do not reach the tumor site. 

• Targeted drug delivery delivers medication in the affected tissues while reducing the relative concentration of the drug in the other tissues. 

• For example, by avoiding the host's defense mechanisms and inhibiting non-specific distribution in the liver and spleen, a system can reach the intended site of action in higher concentrations. Targeted delivery is believed to improve efficacy while reducing side-effects. 

• The concept of targeted drugs was first proposed in 1906 by scientist Paul Ehrlich.

What is drug targeting? 

• The interaction of drug molecules with cell- or cell membrane-related biological events at receptor sites in a concentration-dependent manner determines a drug's therapeutic response. 

• Selective and efficient localization of the pharmacologically active moiety at the pre-identified target(s) in a therapeutic concentration, while preventing access to the non-target(s) normal cellular linings, thereby minimizing toxic effects and maximizing the therapeutic index.

Why it is needed:

Advantages of Targeted Drug Delivery System:

1. Reduced toxicity.

2. Decreased harmful effects. 

3. Smaller dose. 

4. Avoidance of first-pass metabolism. 

5. Increased absorption of large molecules like peptides and proteins. 

6. No peak in plasma concentration. 

7. Selective targeting to infected cells compared to normal cells. 

8. Decreased toxicity of drugs to non-target cells.

Disadvantages of Targeted Drug Delivery System:

1. Requires highly sophisticated technology for formulations. 

2. Requires skilled staff for manufacturing. 

3. Drug deposition at targeted sites may cause toxic symptoms. 

4. Difficult to maintain the stability of the dosage form, E.g. re-sealed RBC at 4°C. 

5. Drug loading is usually low, E.g. micelles, liposomes.

6. High cost of storing and formulating.

Ideal Characteristics for a Targeted Drug Delivery System:

1. Should be non-immunogenic.

2. Should be both physically and chemically stable in vivo and in vitro.

3. should limit the distribution of drugs to organs, tissues, or cell targets.

4. Plasma distribution should be uniform.

5. The drug release rate should be predictable and controllable.

6. Drug release does not affect drug action.

7. Therapeutic amount of drugs should be released.

8. Carriers used must be biodegradable or readily eliminated from the body without a problem and no carrier-induced modulation and diseased state.

9. Preparation should be easy or reasonably simple, reproductive and cost-effective.

Commonly Asked Questions.

1. What is a Targeted Drug Delivery SYstem? Explain its ideal characteristics.

2. Give advantages and disadvantages of Targeted Drug Delivery Systems.

3. Write a short note on Targeted Drug Delivery Systems.