Skip to main content

Renin Angiotensin Mechanism.

Controlled Drug Delivery System: Advantages, Disadvantages, Selection of Drug Candidates.

 

Introduction:

  • Controlled drug delivery is one which delivers the drug at a predetermined rate, locally or systemically, for a specified period of time.

  • The rationale of controlled release dosage form can be summarized as below:

    • To provide a location-specific action within the GIT.

    • To avoid an undesirable local action within the GIT.

    • To provide a programmed drug delivery pattern.

    • To increase the rate and extent of absorption/bioavailability.

    • To extend the duration of action of the drug.

Advantages of Controlled Drug Delivery Systems:

  1. Maintains the drug level within the desired range.

  2. Useful for delivery of ‘difficult’ drugs: the slow release of water-soluble drugs, and/or fast release of poorly soluble drugs,

  3. Reduces dosing frequency,

  4. Avoids over or underdosing,

  5. Prevention or reduction of side effects,

  6. Reduction in total health care cost,

  7. Improved efficacy in the treatment,

  8. Reduction in adverse side effects and improvement in tolerability

  9. Improved patient compliance,

  10. Uses less amount of total drug,

  11. Minimizes or removes local or systemic side effects.

  12. Minimal drug accumulation on chronic usage

  13. Cures or controls the condition more promptly

  14. Reduces the fluctuation in drug level

  15. Improves the bioavailability of some drugs.

Disadvantages of Controlled Drug Delivery Systems:

  1. May be costly,

  2. Unpredictable and often provide poor in-vitro – in-vivo correlations,

  3. May cause dose dumping, if the release design is failed,

  4. Provides less scope for dosage adjustment,

  5. May increase the first pass clearance,

  6. Poor systemic availability in some cases,

  7. Effective drug release period is influenced and limited by the gastric residence time.

  8. All drugs are not suitable for formulating into ER dosage form.

Selection of Drug Candidates for Controlled Drug Delivery Systems:

  • All the drugs cannot be formulated as their controlled release dosage forms. 

  • A drug must have the following characteristics for the formulation of controlled release dosage forms.

Parameter

Preferred Value.

Molecular weight/ size

< 1000

Solubility

> 0.1 μg/ml for pH 1 to pH 7.8

Pka Non ionized moiety

> 0.1% at pH 1 to pH 7.8

Apparent partition coefficient

High

Absorption mechanism

Diffusion

General absorbability

From all GI regions.

Release

Should not be influenced by pH and enzymes

  • Characteristics that may make a drug unsuitable for Control release dosage form,

    • Short elimination half-life

    • Long elimination half-life

    • Narrow therapeutic index

    • Poor absorption

    • Active absorption

    • Low or slow absorption

    • Extensive first pass effect

Commonly Asked Questions.

  1. What is a Controlled Drug Delivery System? Give its advantages and disadvantages.

  2. Give its advantages and disadvantages of Controlled Drug Delivery System. Discuss which drug candidates are suitable for the Controlled Drug Delivery System? 
Labels:

Popular posts from this blog

Rate of Drying Curve.

  Definition Drying is defined as the removal of liquid from a product usually with application of heat. Rate of Drying Curve. Drying process can be divided into three periods Initial Adjustment Period. Constant drying rate period. First falling drying rate period. Second falling rate period. Initial Adjustment Period (A-B): Also called the “ Heating up” period . In this period the substance gets heat and increases in temperature. Drying has not yet started. Constant drying rate period (B-C): During this period the temperature of the solid and the rate of drying remain constant. The moisture evaporating from the surface is replaced by water diffusing from the interior of the solid at a rate equal t o the rate of evaporation.  The moisture content at the end of constant rate (point C) is referred to as the critical moisture content (CMC).  At CMC, dry spots start appearing and drying rate starts falling . First falling drying rate period (C-D): This period is also called the period of
Read more

Heat Exchangers and Heat Interchangers.

  In pharmaceutical industries many types of equipments are used for transfer of heat, they can be classified as follows, Heat Exchangers. Heat Interchangers. Heat Exchangers: These devices are used for transferring heat from a fluid (Hot Gas or Steam) to another fluid (Liquid) through a metal wall. Heat Interchangers: These devices are used for transferring heat from a One liquid to another liquid or one gas to another gas through a metal wall. HEAT EXCHANGERS; The equipment used for heat transferring are known as heat exchangers. Some of the processes that involves heat transfer in pharmaceutical industries are: Preparation of starch paste (in steam jacketed kettle). Crystallization. Evaporation. Distillation.  Classification of heat exchangers On the basis of transfer of heat, heat exchangers are classified as: Direct transfer type:  The hot and cold fluids are separated by a metal wall through which the heat is transferred from hot fluid to cold fluid. E.g. shell and tube heater, 
Read more

Flash Distillation.

  Principle: When a hot mixture is allowed to enter from a high-pressure zone into a low pressure zone, the entire liquid mixture is suddenly vaporized. This process is known as flash vaporization .  During this process, the chamber is cooled.  The less volatile fraction is condensed and the more volatile component remains in the vapor phase .  This process requires time, hence liquid and vapor are kept in intimate contact until equilibrium is achieved. Flash distillation is also called equilibrium distillation because separation of two liquids takes place when liquid and vapor phases are at equilibrium. Equipment used for Flash Distillation: Construction: It consists of a pump, which is connected to a feed reservoir.  Pumps help in pumping the feed into the heating chamber.  The heating chamber is heat supplied by steam.  The other end of the pipe is directly introduced into the vapor-liquid separator through a reducing valve.  The vapor outlet is provided at the top of the separato
Read more