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Pharmacology
 

Pharmacology

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    Pharmacology Pharmacology Presentation Transcript

    • PHARMACOLOGY • PHARMACOLOGY: It is the science which deals with the complete study of drugs, particularly the action of drug on various system of the body • PHARMACOLOGIST: is a doctor, who teaches pharmacology at medical colleges • PHARMACIST: is a technical person, who looks after the manufacture of formulations in the industry • DRUG: It is defined as any substance used for the purpose of diagnosis, prevention, relief or cure of disease
    • PHARMACOLOGY • PHARMACY: It is branch of science of identification, selection, preservation, standardisation, compounding & dispersing of medicine • PHARMACOKINETICS: It is defined as study of the absorption, distribution, metabolism & excretion of drugs & their relationship to Pharmacologic response (What the body does to the drug) • PHARMACODYNAMICS: Which is the quantitative study of the biological & therapeutic effects of drugs (What the drug does to the body) • PHARMACOPOEIA: It is an official code containing a selected list of established drugs & medicinal Preparations Eg. BNF, NF(Indian)
    • ABSORPTION • Passive diffusion (aqueous or lipid environment): most common • Active transport: important for some drugs, particularly larger molecules Aqueous diffusion • Within large aqueous components (e.g.,interstitial space, cytosol)
    • ABSORPTION •Across epithelial membrane tight junctions across endothelial blood vessel lining • Through aqueous pores: allows diffusion of molecules with molecular weights up to 20,000 -30,000 • Driving force: drug concentration gradient
    • ORAL ADMINISTRATION • Most convenient, most economical DISADVANTAGES:  emesis (drug irritation of the gastrointestinal mucosa)  digestive enzymes/gastric acidity destroys the drug  unreliable or inconsistent absorption due to food or other drug effects  metabolism of the drug by gastrointestinal flora
    • ORAL ADMINISTRATION Factors determining rate of drug effect onset Primary factor: • Rate & absorption extent by GI tract • Absorption Site: mainly small intestine because of large surface area
    • DRUG IONIZATION • Non ionized (lipid-soluble) forms favor absorption • Weak acids may be highly ionized in the alkaline intestinal pH (not favoring absorption) but this effect is counterbalanced by the large surface-area effect • Drugs which are weak acids are readily absorbed in the stomach • Uncharged form: lipid-soluble • Charged form: aqueous-soluble, relatively lipidinsoluble (does not pass biological membranes easily)
    • FIRST-PASS EFFECT • Drugs absorbed from the GI tract passes through the portal venous system then through the liver & finally into the systemic circulation, when drugs interact with receptors in target tissues. • Extensive hepatic metabolism/extraction result in minimal drug delivery to the systemic circulation for certain agents
    • FIRST-PASS EFFECT • Drugs with large first pass effect exhibit significant differences in pharmacological effects comparing oral vs. IV administration,Examples: • Propranolol • Lidocaine Avoiding the first-pass effect: • sublingual (e.g. nitroglycerin)-- direct access to systemic circulation • transdermal
    • FIRST-PASS EFFECT Avoiding the first-pass effect: • use of suppositories in the lower rectum {if suppositories move upward, absorption may occur through the superior hemorrhoidal veins, which lead to the liver} • inhalation: first-pass pulmonary loss by excretion or metabolism may occur
    • PARENTERAL ADMINISTRATION • Ensures active drug absorption • Sub-cutaneously intramuscular injection: more rapid/predictable than oral administration route • only route of administration acceptable for: ∗ uncooperative patients ∗ unconscious patients
    • PARENTERAL ADMINISTRATION Advantages of IV administration 1. rapid/precise blood drug levels obtained (e.g., no first-pass effect) 2. Irritant drugs: more comfortably administered (blood vessels relatively insensitive); drug rapidly diluted (particularly if administered into large forearm vein)
    • BIOAVAILABILITY BIOAVAILABILITY: It indicates a measurement of the rate & extent (amount) of therapeutically active drug which reaches the general circulation (The amount of drug available in the blood for action) BIOEQUIVALENT: It means pharmaceutical equivalents or whose rate & extent of absorption do not show a significant difference when administered at the same molar dose of the therapeutic moiety under similar experimental conditions, either single dose or multiple dose
    • AUC
    • AUC Area Under the Curve AUC: It is a measure of the bioavailability of the drug, AUC gives the extent of absorption C max: It is the peak concentration of the drug reached in the plasma T max: It is the time required to reach C max after administration of the drug Plasma Half-life(t1/2): It is the time taken by the drug in the plasma to reduce to 50%(half) from its peak concentration at a particular dosage form
    • HALF- LIFE
    • HALF-LIFE Half-life: (t1/2): It is the time required to decrease the amount of drug in body by 1/2 during elimination (or during a constant infusion) • Useful in estimating time to steady-state • Useful in estimating time required for drug removal from the body • means for estimation of appropriate dosing interval
    • ORAL & IV
    • DRUG RECEPTORS DRUG RECEPTORS: Cell functions are regulated by means of messages substances involved in the transfer of information. These messengers recognized & bind to specific sites on the cell member called as receptors. They are macromolecules proteineous substances, mostly present on the surface of the cell membrane Specific drugs have specific receptors to combine, this combination is known as Drug- Receptor Complex
    • DRUGS RECEPTORS PAETIAL AGONIST: It is a drug with an affinity equal to or less than that of the agonist but less intrinsic activity AGONIST: If the drug is binding to the receptor & initiating a certain activity in the cell then the drug is called as Agonist, E.g Beta receptor agonist – Salbutamol ANTAGONIST:If the drug is binding to the receptor but not initiating any action in the cell then the drug is called Antagonist, E.g Ondensetron – 5 HT3