Introduction general Pharmacology
Friends, welcome all of you to Clinical Trial blog. You might be thinking that “Pharmacology” will be very difficult, so let me tell you that you do not need to panic. In this article, we will learn in simple language what the Pharmacology means. I will tell you the meaning of Pharmacology in simple language.
Pharmacology is divided into two words, Pharmaco means drug and logy means to study. Pharmacology means that it is the study of Pharmacokinetic and Pharmacodynamics.
It is the branch of science which deal with the study of Pharmacodynamic and Pharmacokinetics.
It is all about study of drug and effect of drug on body and body’s response for the drugs.
Now we will learn about the Pharmacokinetic and Pharmacodynamic principles.
Pharmacodynamics in General Pharmacology
Pharmacodynamics means the branch of pharmacology concerned with the effect of drugs and the mechanism of their action .
Pharmacodynamics divided into two Parts : Pharmaco-Drug and Dynamics :effect
In simple language what does drug to the body and Mechanism of drug action to the body.
Pharmacokinetics in General Pharmacology
A subfield of pharmacology that studies how medications go through the body
What does body’s response to the drug
What does body do to the drug
The Four Criteria for Pharmacokinetics :
1.Absorption
2.Distrubution
3.Metabolism
4 Elimination
In short form ADME
Introduction to Pharmacology Definition, Historical landmarks and scope of General Pharmacology:
Definitions:
1.Pharmacology:This field of study focuses on the applications, side effects, and mechanism of action of pharmaceuticals.
2.Clinical Pharmacology: drug research and clinical applications.
3.Drugs: A medications or other material which offer therapies action when taken into body.
4.Pharmacokinetics: It is branch of pharmacology concerned with the movement of drug in body or study about absorption ,distribution ,Metabolism and Excretion of drug in body.
5.Pharmacodynamics: It is branch of pharmacology concerned with the effect of drugs on body.
6.Toxicology: It is branch of science concerned with the study of poisons, toxic substances and their antidote or treatment.
7.Chemotherapy: It is branch in which we study about the chemical use of chemical drugs for the disease(effect of drugs).
8.Adverse reaction: In Pharmacology, any unexpected or dangerous reaction to a drug .
an unintended consequence of taking medication.
9.Bioavailability: The rate and extent of the active substance’s absorption from a pharmaceutical form and availability at the site of action” is the definition of this term.
Historical Landmark in General Pharmacology
The Knowledge of drugs and their uses for diseases are old as history mankind.
Primitive man(Ancient) gather the knowledge of healing and medicines by observing the nature ,noticing the animals while ill and person experience after consuming plants and herbs as remedies.
They discovered that extracts from plants, animals and minerals had medicinal had medicinal effects on body tissue.
Landmark in General Pharmacology
1. Hippocrates (460-375 BC) – A Greek Physician consider “Father of Medicines”.
He was the first person who recognize disease as abnormal reaction of the body.
He introduces the use of metallic salts in medicine.
2. Paracelsus (1493-1541)– Grand father of pharmacology.
He presents the idea of using chemicals to treat illnesses.
Modern in General Pharmacology
1.Oswald schmiedeberg (1838-1921)
Father of Pharmacology
He established Pharmacology as an independent discipline.
Estimation of chloroform in blood.
2.John Jacob Abel (1857-1938)
Isolation of histamine (to start allergic response like vasodilation) from pituitary.
Preparation of pure crystalline insulin.
3.Paul Enrlich (1854-1915)
Paul Enrlich– Nobel Prize winner and Father of chemotherapy.
Find a cure for syphilis in 1909.(Used arsenical in syphilis)
4.Alexandar flemming (1881-1955)
He is Scottish Physician.
He discovered world’s first broadly effective antibiotic substances which is named Penicillin.
5. Ramnath Chopra (1882-1973)
He was an Indian Medical service officer.
Father of Indian Pharmacology.
Systemic study of Indian Medicinal Plant.
Scope of General Pharmacology
SOURCEOFDRUGS:
| SOURCE | SPC. & DRUGS | CATEGORY |
| PLANTS | FOX GLOVE: DIGITALIS | CARDIAC GLYCOSIDE |
| MICROBES | PENICILLIUM NOTATUM: PENICILLIN | ANTIBIOTIC |
| ANIMALS | PORK, BEEF: INSULINE | ANTIDIABETICS |
| MINERALS | GOLD | ANTIARTHRITIS |
| SYNTHETICS | ASPIRIN | ANTI-INFLAMMATORY |
| GENETICAL | HUMAN RECOMBINANT GENE |
DIFFERENT THERAPEUTICS USES OF DRUGS IN GENERAL PHARMACOLOGY
CURATIVE USE:
•DRUG REMOVE CAUSES & ELIMINATE DISEASE.
•Antibiotics destroy organisms and eliminate the causes of infection.
SUPPRESSIVE & SYMPTOMATIC USE:
•DO NOT CURE DISEASE BUT SUPPRESS SYMPTOMS.
•Analgesics relieve arthritis pain, but they do not treat it.
PROPHYLACTIC OR PREVENTIVE:
•PREVENT SPECIFIC PATHOLOGICAL CONDITION.
•ANY VACCINE
DIAGNOSTIC USES:
••THE DIAGNOSIS OR IDENTIFY UNDERLYING PATHOLOGY OR CAUSE OF DESEASE:
•X-RAY FILM, BARRIUM SULPHATE.
AUXILLIARY USE:
•TWO DRUG ADMINISTRATE TOGETHER.
•ONE DRUG SUPORT OTHER.
• PROBENECID REDUCES RENAL ELIMINATION, WHILE PENICILLIN KILLS ORGANISM.
PLACEBO:
•NO ACTIVE CONSTITUTE, ONLY PSYCOLOGICAL TREATMENT.
WHATS HAPPENS TO A DRUG WHEN IT ENTERS IN TO BODY?
ABSORPTION:
SITE OF ADMINISTRATION TO SYSTEMIC CIRCULATION”
BIOAVAIBLITY:
•ALL DRUG THAT IS ADMINISTERED MAY NOT GO INTO THE CIRCULATION
(EXCEPT INTRAVANOUS ROUTE), SOME FRACTION IS WASTED.
“FRACTION OF TOTAL ADMINISTERED DRUG THAT ENTERS INTO
CIRCULATION”
•IT IS THE PARAMETER THAT MEASURES THE RATE AND EXTENT OF ABSORPTION.
•IT IS ALTER BY VARIOUS FACTORS.
DISTRIBUTION IN GENERAL PHARMACOLOGY
TRANSPORT OF DRUG FROM CIRCULATION TO VARIOUS COMPARTMENT” VOLUME OF DISTRIBUTION:
•AFTER ABSORPTION, A FRACTION ATTACHED TO PLASMA PROTEINS AND A
FRACTION REMAINS FREE.
•FREE PORTION IS AVAILABLE FOR DISTRIBUTION ALL OVER BODY.
•TRANSFERRED INTO DIFFERENT COMPARTMENTS LIKE EXTRACELLULAR FLUID OR INSIDE THE CELLS OF DIFFERENT ORGANS.
“SO THE TERM VOLUME OF DISTRIBUTION COVER THE FREE FRACTION OF DRUG INTO
THE CIRCULATION”
IT IS ALSO KNOWN AS APPERENT VOLUME OF DISTRIBUTION BECAUSE IT DOESN’T
INDICATE REAL VOLUME.
Eg: SUPPOSE 500 mg DRUG IS ADMINISTERED BY IV ROUTE AND PLASMA CONC. PRODUCE BY IT IS SUPPOSE 10mg/L THE APPERENT VOLUME OF DISTRIBUTION IS 500/10 = 50L
FACTOR AFFECTING THE DRUG DISTRIBUTION
PLASMA PROTEIN BINDING.
RATE OF BLOOD FLOW IN VARIOUS ORGANS.
CELLULAR BINDING.
CONCENTRATION IN FATTY TISSUE.
BLOOD BRAIN BARRIER
PLASMA PROTEIN BINDING IN GENERAL PHARMACOLOGY
•MOST DRUGS IN THE VASCULAR COMPARTMENT BIND REVERSIBLY TO MACROMOLECULES IN THE PLASMA.
•THESE ARE ALBUMIN, GLOBULIN, TRANSFERRIN, CERULOPLASMIN, GLYCOPROTEINS
AND α AND β LIPOPROTEINS.
•ACIDIC DRUGS MAINLY BINDS TO ALBUMIN, WHEREAS BASIC DRUGS BINDS TO PLASMAPROTEIN AND ALBUMIN.
•BINDING INFLUENCES DRUG DISTRIBUTION, METABOLISM AND ELIMINATION
BECAUSE ONLY FREE DRUG TAKE PART IN P’COKINETIC PROCESSES.
•SO, DRUG CIRCULATE IN BOTH FREE AND BOUND FORM AND HAS DYNAMIC EQUILIBIRIUM BETWEEN THESE TWO FORMS.
•ONLY FREE FORM OF THE DRUG IS PHARMACOLOGICALLY ACTIVE FORMAND DIFFUSE THROUGH CAPILLARY WALLS TO REACH THE SITE OF ACTION.
•SO THE EXTENSIVE BINDING REDUCE THE INTENSITY OF DRUG ACTION.
•SOME DRUGS ARE DISTRIBUTED TO SITES OTHER THAN THE PLASMA.
•LIPID SOLUBLE DRUGS MAY ENTER FAT STORES. Eg: VERAPAMIL, LIGNOCAIN ETC.
•TISSUE BINDING ALSO SEEN AND THIS DELAYS ELIMINATION FROM THE BODY AND PROLONG THE t1/2 OF THE DRUG.
Eg. DIGOXIN BINDS TO CARDIAC MUSCLES AND CHLOROQUINE TO RATINA.
RATE OF BLOOD FLOWS INTO VARIOUS ORGANS IN GENERAL PHARMACOLOGY
•IT INFLUENCE DRUG DELIVERY TO THE SITE OF ACTION.
Eg. IV INJECTION OF A LIPID SOLUBLE DRUG, THE BRAIN CONC. RISE
•RAPIDLY DUE TO GOOD TISSUE PERFUSION AND EQUILIBRIUM BETWEEN FREE AND BOUND DRUG IS ATTAINED.
•IN MUSCLES THESE PHENOMENON HAPPENS SLOWLY.
•SO THE FAT CONTENT MUSCLES RESTRICTED THE BLOOD FLOW SO DRUG ABSORB SLOWLY.
•CONC. OF DRUGS IN FATTY TISSUE IT ALSO INFLUENCES DRUG DISTRIBUTION.
•DRUGS WITH HIGH LIPOPHILICITY GLUTHIMIDE IS STORED IN FAT AND SERVE AS DEPOT. WHEN PLASMA LEVEL OF THE DRUG ARE LOWERED BY METABOLISM, PLASMA LEVEL ARE PROMPTLY RESTORED BY METABOLIZATION OF DEPOT STORAGE SITES.
THE BLOOD BRAIN BARRIER IN GENERAL PHRAMCOLOGY
•CAPILLARIES FOUND IN OTHER PARTS OF THE BODY THE CAPILLARIES IN THE BRAIN ARE HIGHLY SPECIALIZED AND MUCH LESS PERMEABLE TO WATER-SOLUBLE DRUGS.
•THE BRAIN CAPILLARIES CONSIST OF ENDOTHELIAL CELLS WHICH ARE JOINED TO ONE ANOTHER BY CONTINUOUS TIGHT INTERCELLULAR JUNCTIONS COMPRISING WHAT IS CALLED AS THE BLOOD-BRAIN BARRIER.
•MOREOVER, THE PRESENCE OF SPECIAL CELLS CALLED AS ASTROCYTES, WHICH ARE THE ELEMENTS OF THE SUPPORTING TISSUE FOUND AT THE BASE OF ENDOTHELIAL MEMBRANE, FORM A SOLID ENVELOPE AROUND THE BRAIN CAPILLARIES.
•AS A RESULT, THE INTERCELLULAR PASSAGE IS BLOCKED AND FOR A DRUG TO GAIN ACCESS FROM THE CAPILLARY CIRCULATION INTO THE BRAIN, IT HAS TO PASS THROUGH THE CELLS RATHER THAN BETWEEN THEM.
METABOLISM OR BIOTRANSFORMATION OF THE DRUG IN GENERAL PHARMACOLOGY
CONVERSION OF DRUGS INTO A FORM THAT GETS EXCRETED EASILY”
DEPENDING UPON THE BIOLOGICAL ACTIVIRY IT IS CLASSIFIED IN FOLLOWING
WAYS:
1) INACTIVTON:
•CONVERSION OF ACTIVE DRUG IN TO INACTIVE METABOLITES.
2) ACTIVATION:
•IN THIS SITUATION THE METABOLITE IS BIOLOGICALL ACTIVE.
Eg: DIAZEPAM AFTER METABOLISM CONVERT IN TO OXAZEPAM IS ALSO BIOLOGICAL ACTIVE.
•IN SOME CASE PHARMACOLOGICALLY INACTIVE SUBSTANCE AFTER
METABOLISM CONVERT IN TO ACTIVATION FORM.
Eg: L-DOPA IS INACTIVE BUT ITS METABOLITE DOPAMINE IS ACTIVE. THIS TYPE OF DRUG IS KNOWN AS PRO DRUG.
SIGNIFICANCE OF PRODRUGS SIGNIFICANCE OF PRODRUGS IN GENERAL PHRAMCOLOGY
1)PRODRUGS ARE SOMETIMES BETTER ABSORBED THAN DRUGS.
Eg: TALAMPICILLIN IS THE PRODRUG OF AMPICILLIN IS BETTER ABSORBED THAN AMPICILLIN.
2)PRODRUG REDUCE TOXICITY.
Eg: BENORYLATE PRODUCES LESS GI ADVERSE EFFECTS THAN
ASPIRIN.
3)USEFUL FOR THE PROPER DISTRIBUTION.
Eg: L-DOPA CROSS THE BBB WHILE DOPINE NOT.
DEPENDING UPON THE CHEMICAL REACTION IN GENERAL PHARMACOLOGY
ACCORDING TO CHEMICAL REACTION IT IS DEVIDED IN TO TWO PHASE
| PHASE I | PHASE II |
| 1)NON SYNTHETIC REACTION 2)INCLUTE PROCESS LIKE OXIDATION, REDUCTION HYDROLISIS. 3)METABOLITES OF IT CAN BE ACTIVE, INACTIVE OR TOXIC. | 1)SYNTHETIC REACTION 2)CONJUGATION IS THE MAIN CHEMICAL PROCESS 3)METABOLITES OF PHASE II REACTION NECESSARILY INACTIVE. |
1)ELIMINATED UNCHANGED WITHOUT METABOLISM
2)ELIMINATED ONLY BY PHASE I REACTION.
3)ELIMINATE ONLY BY PHASE II REACTION.
ELIMINATE BY PHASE I AND II REACTION.
PHASE I REACTION IN GENERAL PHARMACOLOGY
1)HYDROLYSIS:
DRUG CONTAINIG FUNCTIONAL GROUPS SUCH AS CABOXYLIC ACID, ESTER, AMIDE, THIOESTER, ACID ANHYDRIDE UNDERGO HYDROLYSIS.
2)REDUCTION:
DRUG CONTAINING AN ALDYHIDE, KETONE, DISULFIDE, SULFOXIDE, QUININE, ALKENE ETC ARE UNDERGO REDUCTION.
3)OXIDATION:
IN THIS PROCESS CYTOCHROME P450, NADPH, Fe+3 ETC ARE INVOLVED.
PHASE II REACTION IN GENERAL PHARMACOLOGY
THESE CONJUGATION REACTION INCLUDE GLUCORONIDATION,SULFONATION, ACETYLATION, METHYLATION, CONJUGATION WITH GLUTATHION AND WITH AMINO ACID SUCH AS GLYCIN, GLUTAMIC ACID.
PHASE II REACTION ARE GENERALLY FASTER THAN PHASE I
ELIMINATION OR EXCRETION IN GENERAL PHARMACOLOGY
“REMOVAL OF DRUG FROM BODY”
DRUGS ARE EXCRETED BY DIFFERENT ROOTS:
1) RENAL EXCRETION:
A) GLOMERULAR FILTRATION B) TUBULAR SECRETION C)TUBULAR REABSORPTION
2) FECAL ELIMINATION:
•UNABSORBED PART OF THE DRUGS.
•SOME DRUGS DIFFUSE BACK FROM BLOOD IN TO INTESTINE
•MANY DRUGS GOING TO LIVER ARE SECRETED IN TO BILE AND ELIMINATED.
Eg: NEOMYCIN, DOXYCYCLINE.
3) PULMONARY ELIMINATION:
•MAINLY ALCOHOLIC AND VOLATILE DRUGS.
4) ELIMINATION IN BREAST MILK:
•IT IS NOT SIGNIFICANT FOR THE MOTHER BUT TOXIC FOR BABY.
•MILK IS SLIGHTLY ACIDIC IN NATURE SO BASIC DRUGS ARE PREFERBLY
CONCENTRATED IN MILK.
Eg: CORTICOSTEROID SUPPRESS ADRENAL FUNCTION
CHLORAMPHENICOL GRAY BABY SYNDROM/BONE MARROW DEPRESIONSALIVA, TEARS ARE ALSO THE ADDITIONAL ROUTE OF ELIMINATION
CONCEPT OF CLEARANCE IN GENERAL PHARMACOLOGY
ELIMINATION RATE:
•AMOUNT OF SUBSTANCE REMOVAL FROM THE CIRCULATION PER UNITE TIME.
CLEARANCE (ML/MIN):
•VOLUME OF PLASMA THAT IS CLEARED OF DRUG PER UNIT TIME.
THE RELATION BETWEEN CLEARANCE, ELIMINATION RATE AND PLASMA CONCENTRATION, EXPRESSED AS;
CL=ELIMINATION RATE (µg/min) / PLASMA CONCENTRATION (µg/ml)
TOTAL BODY CLEARANCE = CLRenal + CLHepatic + CLLungs
ELIMINATION KINETICS IN GENERAL PHARMACOLOGY
FIRST ORDER KINETICS OR EXPONETIAL KINETICS:
•WHEN CONCENTRATION OF DRUGS IN BODY INCREASES ELIMINATION RATE IS ALSO INCREASES.
•HERE, THE RATE OF ELIMINATION IS DIRECTLY PROPOSNAL TO
CONCENTRATION.
ZERO ORDER KINETICS:
•HERE, DRUG ELIMINATION RATE IS NOT DEPEND ON TO CONCENTRATION.
•MEANS IF THE CONC. OF DRUGS INCREASE IN BLOOD ELIMINATION DOES NOT INCREASE IN SAME PROPOSION.
•THIS TYPE OF KINETIC KNOWN AS SATURATION KINETICS.
PHARMACODYNAMIC IN GENERAL PHARMACOLOGY
WHAT A DRUG DOES TO A BODY”
DRUGS CAN PRODUCE THEIR EFFECTS IN A VARIETY OF WAYS:
MECHANISM OF ACTION OF DRUGS
PHYSICAL ACTION:
•BULK LAXATIVE ABSORB WATER AND SWELL.
•FORM MASS IN LARGE INTESTINE AND FACILITATE THE PASSAGE OF STOOLS.
CHEMICAL ACTION:
•ANTACIDS NEUTRALIZE ACID IN STOMACH AND REDUCE ACIDITY.
ACTION THROUGH ENZYME:
•MOST COMMON MODES OF ACTION
A) COMPETITIVE ACTION IN GENERAL PHARMACOLOGY:
ANGIOTENSIN I CONVERT IN TO ANGIOTENSIN II BY THE HELP OF ANGIOTENSINOGEN CONVERTING ENZYME (ACE), WHICH PRODUCE VASOCONSTRICTION.
LISINOPRIL IS STRUCTURLY SIMILAR TO ANGIOTENSIN I SO ACE BIND WITH LISINOPRIL AND INHIBIT THE CONVERSION FROM IANGIOTENSIN I TO II.
B) NON COMPETITIVE ACTION IN GENERAL PHARMACOLOGY :
•CYCLOOXIGENASE IS THE ENZYME PRODUCE PROSTAGLANDIN, THE SUBSTANCE REQUIRE FOR THE INFLAMATION.
NSAIDS (IBUPROFEN, DICLOFENAC, ETC) INHIBITE THE ENZYME AND PREVENT FORMATION OF ENZYME AND REDUCE INFLAMATION
C) ACTION BY STIMULATING ENZYME:
•DRUGS LIKE STEPTOKINASE OR UROKINASE STIMULATE ENZYME
PLASMINOGEN AND PROMOTE BREAKDOWN OF BLOOD CLOT.
ALTERATION IN TRANSPORT SYSTEM:
•DRUG CAN ALTER ENTRY AND EXIT OF DIFFERENT IONS INSIDE CELLS.
Eg: CALCIUM CHANNEL BLOCKERS LIKE NIFEDIPINE, VERAPAMIL PREVENT ENTRY OF CALCIUM INSIDE CELL AND PREVENTS CONTRACTION OF MUSCLES.
SPECIFIC ACTION:
A)DRUGS CAN ALTER CONSTITUTION OF CELL MEMBRANE.
Eg: GENERAL ANEASTHETICS ALTER LIPIDS, PROTEINS AND WATER IN THE NERVE CELL MEMBRANE AND PRODUCE ANEASTHETICS ACTION.
B)DRUGS CAN ALTERS SPECIFIC METABILIC PROCESSES INSIDE THE HUMAN CELL AND AFFECT THE MICROORGANISM. Eg: PENICILLINS INHIBIT THE CELL WALL SYNTHESIS OF THE MICROORGANISM BUT NOT THAT ACTION ON HUMAN CEL WAL
RECEPTORS IN GENERAL PHARMACOLOGY
•MOST OF THE DRUGS PRODUCE THEIR ACTION THROUGH RECEPTORS.
•IT IS A MACROMOLECULES RESIDE ON THE SURFACE OF THE CELL OR INSIDE THE CELLS.
•BINDS TO SPECIFIC MOLECULES AND PRODUCE SPECIFIC EFFECTS.
“IT IS THE SITE THAT PROVIDES SPACE FOR ATTACHMENT OF SOME SUBSTANCE AND REGULATE THE FUNCTIONING OF THE CELL”
PHYSIOLOGICAL RECEPTORS:
•PROVIDE SITE FOR PHYSIOLOGICAL SUBSTANCE ATTACHMENT Eg: ADRENERGIC RECEPTORS PROVIDE SPACE FOR ADRENALINE.
DRUG RECEPTORS IN GENERAL PHARMACOLOGY:
•PROVIDE SITE FOR SPECIFIC DRUG ATTACHMENT
Eg: BENZODIAZEPINE GET ATTACHED TO BENZODIAZEPINE RECEPTORS.
AFFINITY IN GENERAL PHARMACOLOGY:
•CAPACITY OF SUBSTANCE TO GET ATTACHED TO THE RECEPTORS Eg: ADRENALINE HAS AFFINITY FOR ADRENERGIC RECEPTORS
INTRINSIC ACTIVITY IN GENERAL PHARMACOLOGY:
•CAPACITY OF SUBSTANCE TO BRING OUT SOME CHANGES (OR PRODUCE
SOME ACTION) AFTER GETTING ATTACHED TO RECEPTORS.
Eg: ADRENALINE AFTER ATTACHED TO ADRENERGIC RECEPTORS GENERATE CYCLIC AMP AND INCREASE FORCE OF CONTRACTION AND HEART RATE.
•ACTION AND EFFECT ARE TWO DIFFERENT, ACTION MEANS CHANGES AFTER BINDING AND EFFECT MEANS BIOLOGICAL EFFECTS OBSERVED AFTER ADMINISTRATION OF DRUG.
AGONIST IN GENERAL PHARMACOLOGY:
•ATTACED TO RECEPTORS AND PRODUCE CONFERMATIONAL CHANGES IN RECEPTORS.
•IT HAS AFFINITY AND INTRINSIC ACTIVIRY.
Eg: ADRENALINE AFTER ATTACHED TO ADRENERGIC RECEPTORS GENERATE CYCLIC AMP AND INCREASE FORCE OF CONTRACTION AND HEART RATE, SO IT IS THE AGONIST OF ADRENERFIC RECEPTORS.
COMPETITIVE ANTAGONIST IN GENERAL PHARMACOLOGY:
•SUBSTANCE HAVE AFFINITY BUT NOT INTRINSIC ACTIVITY.
Eg: PROPANOLOL PREVENT THE ATTACHMENT OF ADRENALINE AND PREVENT
INCREASE HEART RATE OR REDUCE HEAR RATE.
•THESE SUBSTANCE ARE STRUCTURLY SIMILAR
PARTIAL AGONIST:
•IT HAS BOTH AFFINITY AND INTRINSIC ACTIVITY BUT INTRINSIC ACITIVITY IS LESS THAN AGONIST.
INVERSE AGONIST:
•PRODUCE ACTION BUT OPPOSITE TO AGONIST.
SPARE RECEPTORS:
SILENT RECEPTORS:
REGULATION OF RECEPTORS IN GENERAL PHARMACOLOGY
DOWN REGULATION:
WHEN RECEPTORS EXPOSED TO AGONISTS FOR A LONG TIME, THE NUMBER OF RECEPTORS AND THEIR SENSITIVITY FOR AGONIST ARE REDUCED.
WHEN THE AGONIST IS DISCONTINUED, THE ACTIVITY OF RECEPTORS REAPPEARS.
Eg: SALBUTAMOL IS USFUL FOR ASTHAM WHEN IT GIVEN IT PRODUCE DILATION OF BRONCHIAL MUSCLES THROU RECEPTORS BUT AFTER A PROLONG TIME ITS ACTION GET DECREASED BY DECREASIN SENSITIVITY TOWARDS THE RECEPTORS.
UP REGULATON: RECEPTORS ARE BLOCKED FOR A LONG TIME, THE NUMBER AND SENSITIVITY OF THE RECEPTORS FOR AGONIST ARE INCREASED
GENE ASSOCIATED RECEPTORS:
•THESE RECEPTORS ARE SITUTED INSIDE THE CELL AND ARE ACCOSIATED WITH GENES.
Eg: STEROID.
G PROTEIN COUPLED RECEPTORS:
•G PROTEINS MEANS GTP ACTIVATED RECEPTORS.
•G PROTEIN ARE OF DIFFERENT TYPES.
•AGONIST STIMULATE RECEPTORS, STIMULATED RECEPTORS PRODUCE ACTION G PROTEIN IN FOLLOWING PATHWAY:
ACTION THROUGH ADENYL CYCLASE AND Camp:
Eg: DOPAMINE RECEPTORS, H2 RECEPTORS. AGONIST
ACTION THROUGH IP3/DAG IN GENERAL PHARMACOLOGY:
