Fusion protein

Fusion proteins are produced by the combination of two genes or proteins or peptides. They can exist naturally or can be prepared in the laboratory.

PEGylated dosage forms

PEGylated dosage form refers to the attachment of the polythylene glycol polymer chains to a drug concealing the agent from the immune sytem of the body reducing immunogenicity resulting in prolonged circulatory time.

Examples:
PEGylated interferon alpha is in use for the treatment of hepatitis B and C.
PEGylated liposome having doxorubicin is used in the treatment of cancer.

Ophthalmic Inserts

Ophthalmic inserts are solid or semisolid sterile preparations for placement in the conjunctival sac of the eye. These are sustained release drug delivery systems for the eye.

Osmotic Systems

Osmotic systems make use of osmotic pressure for controlled delivery of active ingredients.
This method can be used both for systemic and targeted drug delivery.

Mechanism:
Osmotic pressure as a result of imbibitions of the fluid by the osmotic agents directly affects the rate of drug delivery from osmotic systems such as osmotic pumps.

Components of Osmotic Pump:
1. Drug
2. Osmotic agent or osmogent such as magnesium sulfate, sodium chloride or sodium bicarbonate
3. Semipermeable membrane
4. Plasticizers such as polyethylene glycols, triethyl citrate or ethylene glycol monoacetate

Factors affecting Osmotic drug delivery:
1. Size of the opening of delivery point
2. Solubility of the components
3. Intrinsic character of the rate controlling membrane
4. Osmotic pressure of the components

These factors are important to develop an optimized and desired osmotic system.

Mucoadhesive system

Mucoadhesion refers to adhesion with with moist lining in the body passages of mammals containing cells which secrete mucus and opens to the external environment.

Mucoadhesive system refers to the adhesion of natural or synthetic polymer and soft tissues of mucous membrane for an extended period. Cross linked polymer device, containing drug, will adhere to biological membrane and will transfer the drug to the body at the given site, decreasing frequency of administration.

Theories of mucoadhesion:
Following theories have been proposed in the mucoadhesion of the drug:
1. The wetting theory
2. The diffusion theory
3. The electronic theory
4. The adsorption theory
5. The cohesive theory
6. The Fracture theory
7. The mechanical theory

Controlled release microchips

It represents the slow and controlled release of medicaments from microfabricated device. These are the types of small programmable devices.

In this microchip, micrometer scale pumps, valves and flow channels are incorporated or microfabricated into the active devices. Microchip of solid state silicon can be used in this technique. These microchips have following properties:

1. They can store a large amount and number of chemicals or medicaments
2. They have the ability of controlling the time of release of chemicals or medicaments
3. They have the ability of controlling the rate of release of chemicals or medicaments

These microchips have a tiny power supply. The control of microchips are done by remote control, microprocessors and/or biosensors.

The chemical release takes place through electrochemical dissolution of membranes of thin anode covering microreservoirs which are filled with chemicals in the form liquid, solid or gel.

Uses:
This microchip technology has found uses in many areas such as chemical detection, drug delivery, medical diagnostics and combinatorial chemistry.

References:
January 20, 1999. A commentary on the controlled release microchip. http://web.mit.edu/newsoffice/1999/microchipcom.html. Accessed March 28, 2011.
Santini, J. T. Jr.; Cima, M. J.et al. 1999. A controlled-release microchip. Nature, 397, Pages 335-338.

Santini, J. T. Jr.; Richards, A. C. et al. 2000. Microchips as Controlled Drug-Delivery Devices. Wiley-VCH, 39, Pages 2396-2407.

Phonophoresis

It represents the use of ultrasound for the delivery of drugs through the skin. Through this process topical application of anti-inflammatory drugs and analgesics can be increased.