Advantages and Disadvantages of Implantation Therapy

Implants possess several advantages, but also disadvantages, as drug delivery systems depending on the nature of the drug being delivered. A brief overview of both the advantage and disadvantages of implantable drug delivery is given below.

Advantages:

The advantages of implantation therapy include.

Convenience:-
Effecting drug concentrations in the bloodstream can be maintained for long periods by methods such as continuous intravenous infusion or frequent injections. However, under these regimens patients are often required to stay in hospital during administration for continuous medical monitoring. A short-acting drug exacerbates the situation, as the number of injections or the infusion rate must be increased, in order to maintain a therapeutically effective level of the drug. In contrast, implantation therapy permits patients to receive medication outside the hospital setting with minimal medical surveillance. Implantation therapy is also characterized by a lower incidence of infection related complications in comparison to indwelling catheter-based infusion system

Compliance:
By allowing a reduction, or complete elimination, of patient-involved dosing compliance is increased immensely. A person can forget to take a tablet, but drug delivery from an implant is largely independent of patient input. Some implantable systems involve periodical refilling but despite this factor the patient has less involvement in delivering the required medication.

Potential for controlled release:-
Implants are available which deliver drugs by zero-order controlled release kinetics. Zero order controlled release offers the advantages of

(a)    Avoiding the peaks (risk of toxicity) and troughs (risk of ineffectiveness) of conventional therapy;
(b)    Reducing  the dosing frequency;
(c)    Increasing patient compliance.

Potential for intermittent release:
Externally programmable pumps can facilitate intermittent release. Intermittent release can facilitate drug release in response to such factors as :

(a)    Circadian rhythms;
(b)    Fluctuating metabolic needs;
(c)    The pulsatile release of many peptides and proteins.

Potential for bio-responsive release:
Bio-responsive release from implants is an area of ongoing research.

Improved drug delivery:
Using an implant system the drug is delivered locally or to be systemic circulation with minimal interference buy biological or metabolic barriers. For example, the drug moiety by passed the gastrointestinal tract and the liver. The bypassing effect is particularly of benefit to drugs, which are either absorbed poorly or easily inactivated in the gastrointestinal tract and/or the liver before systemic distribution.

Flexibility:
Considerable flexibility is possible with these systems, in the choice of materials, methods of manufacture, degree of drug loading, drug release rate  etc.

Commercial an implantable dosage form diversifies the product portfolio of a given drug. From a regulatory perspective, it is regarded as a new drug product and can extend the market protection of the drug for an additional 5 years (for a new drug entry) or 3 years (for existing drugs)

Disadvantages:

The disadvantages of implantation therapy include such factors as:

Invasive:
Either a minor or a major surgical procedure is required to initiate therapy. The requires the appropriate surgical personnel, and may be traumatic, time-consuming. Cause some scar formation at the site of implantation and in a very small portion of patient may result in surgery-related complications. The patient may also feel uncomfortable wearing the device.

Termination:
Non-biodegradable polymeric implants and osmotic pumps also be surgically retrieved at the end of treatment. Although a biodegradable polymeric implant does not require surgical retrieval. its continuing biodegradation makes it difficult to terminate drug delivery. or to maintain the correct does at the end of its lifetime.

Danger of device failure:
There is no concomitant danger with this therapy that the device may for some reason fail to operate. which again requires surgical intervention to correct.

Limited to potent drugs :
The size of an implant is usually small. in order to minimize patients discomfort. Therefore most systems have a limited loading capacity so that often only quite potent drugs such as hormones. May be suitable for delivery by implantable devices.

Possibility of adverse reactions:
The site of implantation receives a high concentration of the drug delivered by an implant. This local high drug concentration may trigger adverse reactions.

Biocompatibility issues:
Concerns over body responses to a foreign material often raise the issues of biocompatibility and safety of an implant.

Commercial disadvantages:
Developing an implantable drug delivery system requires an enormous amount of R&D investment in terms of cost, effort and time. If a new biomaterial is proposed to fabricate an implant its safety and incompatibility must be thoroughly evaluated to secure the approval of regulatory authorities. These issues can attribute to significant delay in the development marketing and cost of a new implant.