Advantages Of Novel Drug Delivery Systems Biology Essay

For many a years the treatment of an acute disease or a chronic disease has been mostly accomplished by the delivery of drugs using various dosage forms such as tablet, capsules, pills, suppositories, ointments, liquids, aerosols, and injectables. All these are the conventional drug delivery systems. These systems are the primary pharmaceutical products commonly seen in the prescriptions and they will be available as over the counter. The release of these drug delivery system shows significant fluctuation in drug levels in the body. To avoid these several technical advancements have resulted in the development of new techniques for drug delivery. These techniques are capable of controlling the rate of drug delivery, sustaining the duration of therapeutic activity and the most important one targeting the delivery of drug to a tissue. These are known as novel drug delivery systems and they have revolutionized the method of medication which provides a number of therapeutic benefits1.

1.2 Advantages of novel drug delivery systems

These systems

Improves the therapy by increasing the duration of action and reducing the side effects.

Increases the patient compliance and provides convenient route of administration.

Achieve the targeting of drugs to a specific sites which reduces the unwanted side effects and obtain maximum efficacy.

Reduces the dose and thus reduces the side effects of drugs.

1.3 Types of novel drug delivery systems2

There are number of novel drug delivery systems are available. They are

1. Hydrogels

2. Colloidal drug carrier systems

a) Micelles

b) Microspheres

c) Nanoparticles

Liposomes and neosomes

3. Mucoadhesives

4. Transdermal drug delivery

5. Ocular drug delivery

6. Nasal drug delievery

1. Hydrogels

Hydrogels are three dimensional hydrophilic polymeric networks capable of absorbing large amount of water or biological fluids. These networks are composed of homopolymers or copolymers and are insoluble because of the presence of chemical or physical crosslinks like entanglements or crystallites. The hydrogels exhibit thermodynamic compatibility with water which allows them to swell in aqueous medium. They are used to control the drug release in reservoir based controlled release system or as carriers in swellable and swelling control release devices3.

2. Colloidal drug carrier systems

Colloidal drug carrier systems like micellar solutions, vesicle and liquid crystal dispersions, microspheres, nanoparticles, consisting of small particles, ranging from 10nm to 400nm diameter. They show great promise as drug delivery systems. When developing these formulations the aim is to obtain systems with optimized drug loading and release properties, long shelf life and low toxicity.

a) Micelles

Micelles formed by the self assemble of amphiphilc block copolymers in aqueous solutions. The size ranges from 5 to 50 nm. They will provide grate interest in drug delivery applications. The drugs can be physically entrapped in the core of block co polymer micelle and transported at concentration that can exceed their intrinsic water solubility.

b) Microspheres

Microspheres are the delivery systems that contain a matrix of the polymer in which the drug in micron size is uniformly dispersed. Microcapsules are those where the drug is coated with the polymer. The microcapsules and microspheres prolong drug release where as microspheres are used for drug targeting4.

c) Liposomes and niosomes

Liposomes are a form of vesicles that consists of many or one phospholipid bi layer the polar character of the liposomal core enables polar drug molecules to be encapsulated. Amphiphillic and lipophilic molecules are solubilised with in the phospholipid bi layer according to their affinity towards phospholipids. Presence of non ionic surfactant instead of phospholipids in the formation of bilayers results in the formation of neosomes.5

d) Nanoparticles

The size ranges from 10 to 1000nm. They can absorb and encapsulate a drug thus protecting it from chemical and enzymatic degradation. The nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a unique polymer membrane. Nanospheres are matrix systems in which the drug is physically and uniformly dispersed. Nanoparticles as drug carriers will be formed from both biodegradable and non biodegradable polymers. They will provide massive advantages regarding drug targeting, delivery, and release6.

3. Mucoadhesive systems

Mucoadhesives are synthetic or natural polymers that interact with the mucus layer covering the mucosal epithelial surface and mucin molecules. They can adhere to the gastric mucosa or the buccal mucosa. This concept has altered the possibility that these polymers can be used to overcome physiological barriers in long term drug delivery. This mucoadhesive drug delivery system gives more effective and safe treatment not only for topical disorders but also for systemic problems7.

4. Transdermal drug delivery

Transdermal drug delivery is the administration of drugs across the skin. If the skin is the site of action then high concentration of drugs can be localized at the skin, which results in reducing the systemic drug levels and also reducing the systemic side effects. It is an alternative route for the delivery of systemically acting drugs. This route have several advantages when compared with oral drug administration. It bypasses the lever there by the dose is reduced and the side effects are minimized 8

5. Ocular drug delivery

Ocular drug delivery is the one of the most challenging drug delivery system. This field has improved significantly over the past 20 years. The improvements have largely focused on maintaining the drug in eyes for an extended period of time un like conventional eye drops.

6. Nasal drug delivery.

The nasal route appears to be an alternative to parenterals for administrating drugs intended for systemic effects9. The nasal route provides rich vascularity high permeable structure for absorption. It avoids hepatic first pass metabolism. Proteins such as insulin are reported to have fast and sustained action when administered through the nasal route.

1.4 Targeted drug delivery systems

The word drug targeting was put forward by Dr. Paul ehrlich. Most of the drugs introduced to clinical medicine produce their effects by interacting with cell and cell membrane related structures and function through concentration dependent, reversible interactions at specific receptor sites10-11. To obtain a desirable therapeutic response the correct amount of the drug should be transported to the site of action with the control of drug input rate. The efficacy of many drugs is limited by their potential to reach the therapeutic site of action. In most cases only a small amount of the administered dose of the drug reaches to the site. While most of the drug is distributed to the rest of the body.

Most of the drugs when administered in conventional or controlled release dosage forms, they will travel freely throughout the body leading to uptake by cells tissues or organs. This distribution of the drug to other tissues is unnecessary, wasteful and causes severe toxicity. This lack of target specificity can be attributed to the barriers that the body presents to a drug.