Sunday, 9 June 2013


It can be defined as the process of development of new medical entity or it can also be defined as the process of developing a new improved medical entity for a existing medicine .it is the blanket term used for defining the process of introducing new drug to the market .broadly drug development can be done into two parts:
  1. Preclinical
  2. clinical
preclinical studies are based on NEW DRUG ENTITY these are the compound which emerge from the process of drug discovery .these will have promising activity against particular biological target thought to be important in disease ,however little will be known about the safety ,toxicity,pharmacokinetic and metabolism of this NCE  .while increasingly these test can be made by experimenting  animals .it is legal requirement that an assessment of major organ toxicity be performed as well as effects on other body parts that might be affected by the drug. many test can only be made by using experimental animals , since it is only in an intact organism that the complex interplay of metabolism and drug exposure on toxicity can be examined 
Clinical trials often involve patients with specific health conditions who then benefit from receiving otherwise unavailable treatment .in early phases participants are healthy volunteers who receive financial incentive for their participation .during dosing period study subjects typically remain on the site at the unit for duration of 1 to 40 days and occasionally longer,although this is not always the case 
usually one or more pilot experiment are conducted to gain insight for design of the clinical trial to follow . in medical jargon , effectiveness is how well a treatment work in practice and efficacy is how well it work in a clinical trial .in the us the elderly comprise only 14% of the population .but they consume  over one third of the drugs . in coordination with the panel of experts investigation ,the sponsor decide what to compare the new agent and what kind of patient will be benefited with that product . if the sponsor cannot obtain enough patient with the specific disease or condition at one location who can obtain same kind of patient to receive the treatment would be recruited into study 
The clinical aspect of drug development is usally dependent over various phases which are on both animals and humans these tests are based on three phases which can be given as follows :
  1. PHASE 0
  2. PHASE 1
  3. PHASE 2
  4. PHASE 4
Phase o is a recent designation for exploratory  ,first in human trials conducted in accordance with the united state food and drug administration guideline on exploratory investigational new drug study. PHASE 0 trial are also known as human micro dosing studies and are designed to speed up the development of promising drugs or imaging agent by establishing very on weather drug or agent  behave in human subjects as was expected from preclinical studies . deceptive feature of phase 0 trial include the administration of single subtherapeutic dose of study drug to a smaller no of subjects to gather preliminary data on the agents Pharmacodynamics and pharmacokinetics
A Phase 0 study gives no data on safety or efficacy ,being by definition a dose  too low causes any therapeutic effect . drug development companies carries out Phase 0 studies to rank the candidate in order to decide which has the pest pharmacokinetic parameters in human to take forward into further development 
Phase 1 trials are the first stage of testing in human subjects .normally a small group of 20-100 healthy volunteers well be recruited this phase is designed to asses the safety , tolerability , pharmacokinetics and pharmacodynamics of a drugs . these trials are often conducted in clinics where the subject is observed full time staff . this phase also include dose -ranging also called dose escalation study ,so that the best dose and safest dose can be found .
once a dose or range of dose is determined the next goal is to evaluate weather the drug have any bio logical  activity of effect . phase 2 trials are performed on the lager group of individuals ie 100-300 and are designed to find out that how well the drug is performing 
Phase 2 studies are sometimes divided into phase 2 A and Phase 2 B
Phase 2a is specifically designed to assess dosing requirement 
Phase 2b is designed he efficacy of drug
Phase 3
is generally designed to assess the effectiveness of new intervention and there its value in clinical practice .phase 3 studies are randomize controlled multicenter trials on large patient groups 300-3000 and are aimed at being the definitive assessment of how effective the drug is. becoz of there size the phase 3 trials are very long ,most expensive ,time consuming and difficult trials to run and design
Phase 4
these trials are also known as post marketing surveillance trial . phase 4 trial involve safety surveilance and ongoing technical support of a drug after it receive permission to be sold . these trial may be under taken by sposering company or regulatig authority 

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