What is agonist, antagonist, Partial agonist?

Agonist:
A drug that binds with receptor and activate them to produce a pharmacological response is called agonist.

Antagonist:
Drugs that bind with receptor but no activating effect are termed antagonist.

Partial antagonist:
Drugs that bind with receptor and are capable of exert low degree of activity are termed partial agonist.

What are the difference between alkaloid and glycoside?

Alkaloid	Glycoside
1. Alkaloids are basic nitrogenous compound of plant origin.	1. Glycosides are condensation products of a sugar and non sugar part.
2. Soluble in alcohol not in water	2. Solubility depends on sugar part present in that particular glycoside
3. It give salt with acid	3. Does not form salt with acid
4. Name of alkaloids usually ends in –ine	4. Name of glycosides usually ends in –in.

What is plasma half life? What are the importance of plasma half life?

Plasma half life:
It is the time by which plasma concentration of a drug reduced to it's half.

Importance:

• Plasma half life gives idea about
• Duration of action of drug
• Amount of drug to be administered
• Frequency of administration
• Useful in estimating the time to steady state.
• Useful in estimating time required for drug removal from the body.
• Useful in estimation for appropriate dosing interval.

What is bioavailability? Significance of bioavailability. Factors modifying bioavailability.

Bioavailability: The rate at which and the extent to which the unchanged drugs become available for systemic action at the site of action, following administration is called bioavailabilty.

Significance of Bioavailability: 

• For comparing different formulation of same drug.
• For comparing different formulation of same drug produced by different companies.

Factors modifying bioavailability:

• Pharmaceutical factors
• Physical state of drug and particles size.
• Formulation properties.
• Manufacturing variability.
• Presystemic elimination.
• Enterohepatic circulation of drug.
• Biological factors.

What is prodrug? Advantages of prodrug.

Prodrug: Drugs which do not produce any pharmacological effect until they are chemically altered within the body are called prodrug.

Advantages of prodrug:

• Improve absorption from the site of administration.
• Avoid first pass metabolism.
• Reduce local adverse effects of drugs.
• Improve bio-availability of the drug.
• To overcome pharmaceutical formulation.  

What is partition co-efficient.

Partition co-efficient is defined as the ratio of the concentration of the agent in two phases. The movement of drug through biological membrane depends on the partition co-efficient.
e.g. Lipid water partition co-efficient.

What is ionizing constant or PKa of a drug

Ionizing constant or PKa:

The Pka of a drug is that P^H , at which the concentration of ionized and non-ionized form are equal.

Ionization of the drug depends on the Pka of the drug and p^H of the media.

What are the types of glycosides

Types of glycosides:

1. Cardiac glycosides; e.g. Digitalis
2. Aminoglycosides: e.g. Streptomycin
3. Sennoside: e.g. Selicin

Difference between Alkaloid and Glycoside

Alkaloid	Glycoside
1. Alkaloids are basic nitrogenous compound of plant origin	1. Glycosides are condensation products of a sugar and a non-sugar part.
2. Soluble in alcohol, not in water	2. Solubility depends on sugar part
3. It gives salt with acid	3. Does not form salt with acid
4. Name of alkaloids usually ends with –ine	4. Name of glycosides usually ends with -in

Define Drugs. Discuss different sources of drug with example.

Drug: Any substance or product that is used or intended to be used to modify or explore physiological system or pathological states for the benefit of the recipient is called drug. The benefit of the recipient includes:
1. The diagnosis of disease. e.g. Barium salt, Lopamodol
2. The prevention of disease. e.g. Vaccines
3. The control of disease. e.g. Insulin to control diabetes, Anti-hypertensive to control hypertension.
4. The treatment of disease. e.g. Antibiotics to treat infection.

Sources of drugs:

1. Natural
1. Animal source. e.g. Insulin, Heparin, Gonadotropin
2. Plant source. 
• Alkaloids. e.g. Atropine, Morphine, Ergotamine
• Glycosides. e.g. Digoxin, Digitoxin.
• Oil. e.g. Olive oil, Castor oil
• Tannin. e.g. Tincture of catechu
3. Minerals. e.g. Ferous Fumerate, Liquid paraffin
4. Micro-organism. e.g. Penicillin, Chloramphenicol, Tetracycline
2. Synthetic. e.g. Aspirin, Sulfonamides, Paracetamol
3. Semi synthetic. e.g. Pethidine, Ampicillin
4. Recombinant DNA technology. e.g. Human Insulin