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What is Pharmacology?

What is Pharmacology?. derived from the Greek word for drug A science that studies drug effects within a living system, biochemical and physiological aspects

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What is Pharmacology?

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  1. What is Pharmacology? • derived from the Greek word for drug • A science that studies drug effects within a living system, biochemical and physiological aspects • Deals with all drugs used in society today, legal or illegal, including street, prescription, and non-prescription or over –the-counter medications

  2. Drug • A drug is defined as any substance; chemical agent; used in the • Diagnosis • Cure • Treatment • prevention of a disease or condition

  3. Drug Names • Chemical Name • Generic Name • Trade Name

  4. Chemical Name • Describes its molecular structure and distinguishes it from other drugs

  5. Generic name • Determined by the pharmaceutical company along with a special organization known as the U.S. Adopted Names Council (USAN)

  6. Trade Name • Or brand name- the manufacturer selects alone…can become a registered trademark. • They are the only one who can advertise and market the drug under that name.

  7. How is the Trade Name Chosen? • The particular spelling of a brand name drug is proposed by a manufacturer for one of several reasons.

  8. 1. To indicate the disease process being treated • Azmacort- treats asthma • Rythmol- treats cardiac arrhythmias

  9. 2. To simplify the generic name • Pseudoephedrine to Sudefed • Haloperidol to Haldol • Ciprofloxacin to Cipro

  10. 3. To indicate the duration • Slow-K slow release potassium supplement

  11. Prescription Drugs • Or legend drugs • Means in order to obtain drug, you must have a legal prescription

  12. Non-Prescription Drugs • Or Over-the-Counter (OTC) drugs • Drug that may be purchased without a prescription

  13. Sources of Drugs Drugs have been identified or derived from four main sources: • Plants • Animals • Minerals and Mineral Products • Synthetic or Chemical Substances Made in the Laboratory

  14. Routes of drug administration

  15. Important Info Routes of Drug Administration The route of administration (ROA) that is chosen may have a profound effect upon the speed and efficiency with which the drug acts

  16. The main routes of drug entry into the body may be divided into two classes: • Enteral • Parenteral

  17. Enteral Routes • Enteral- drug placed directly in the GI tract: • sublingual - placed under the tongue • oral - swallowing (p.o., per os) • rectum - Absorption through the rectum

  18. Sublingual/Buccal Some drugs are taken as smaller tablets which are held in the mouth or under the tongue. • Advantages • rapid absorption • drug stability • avoid first-pass effect

  19. Sublingual/Buccal • Disadvantages • inconvenient • small doses • unpleasant taste of some drugs

  20. Oral • Disadvantages • Sometimes inefficient - only part of the drug may be absorbed • First-pass effect - drugs absorbed orally are initially transported to the liver via the portal vein • irritation to gastric mucosa - nausea and vomiting

  21. Oral • Disadvantages • destruction of drugs by gastric acid and digestive juices • effect too slow for emergencies • unpleasant taste of some drugs • unable to use in unconscious patient

  22. First-pass Effect • The first-pass effect is the term used for the hepatic metabolism of a pharmacological agent when it is absorbed from the gut and delivered to the liver via the portal circulation. • The greater the first-pass effect, the less the agent will reach the systemic circulation when the agent is administered orally

  23. First-pass Effect Magnitude of first pass hepatic effect:Extraction ratio (ER) ER = CL liver / Q ; where Q is hepatic blood flow (usually about 90 L per hour. Systemic drug bioavailability (F) may be determined from the extent of absorption (f) and the extraction ratio (ER): F = f x (1 -ER)

  24. First-pass Effect

  25. RECTAL ADMINISTRATION: • Absorption across the rectal mucosa occurs by passive diffusion. • This route of administration is useful in children, old people and unconscious patients. • Eg., drugs that administered are: aspirin, acetaminophen, theophylline, indomethacin, promethazine & certain barbiturates. KLECOP, Nipani

  26. Rectal Advantages: Suitable for unconscious patients and children 2. suitable if patient is nauseous or vomiting 3. easy to terminate exposure 4. good for drugs affecting the bowel such as laxatives Disadvantages: absorption may be variable irritating drugs contraindicated

  27. Parenteral Routes • Intravascular (IV, IA)- placing a drug directly into the blood stream • Intramuscular (IM) - drug injected into skeletal muscle • Subcutaneous- Absorption of drugs from the subcutaneous tissues • Intrathecal : into CSF

  28. Intravascular Absorption phase is bypassed (100% bioavailability) 1.precise, accurate and almost immediate onset of action, 2. large quantities can be given, fairly pain free Disadvantages a-. greater risk of adverse effects b-high concentration attained rapidly C- risk of embolism

  29. Intramuscular 1. very rapid absorption of drugs in aqueous solution 2. Slow release preparations Disadvantages pain at injection sites for certain drugs

  30. Subcutaneous slow and constant absorption 2. absorption is limited by blood flow, affected if circulatory problems exist 3. concurrent administration of vasoconstrictor will slow absorption

  31. Inhalation 1. gaseous and volatile agents and aerosols 2. rapid onset of action due to rapid access to circulation a. large surface area b. thin membranes separates alveoli from circulation c. high blood flow

  32. Topical • Mucosal membranes (eye drops, antiseptic) • Skin • a. Dermal - rubbing in of oil or ointment (local action, sun screen, an callus removal) • b. Transdermal - absorption of drug through skin (systemic action) • i. stable blood levels • ii. no first pass metabolism • iii. drug must be potent or patch becomes too large

  33. Intra nasal administration • Drugs generally administered by intra nasal route for treatment of local condition such as perennial rhinitis, allergic rhinitis and nasal decongestion etc.

  34. Route for administration -Time until effect- • intravenous 30-60 seconds • intraosseous 30-60 seconds • endotracheal 2-3 minutes • inhalation 2-3 minutes • sublingual 3-5 minutes • intramuscular 11-30 minutes • subcutaneous 14-30 minutes • rectal 5-30 minutes • ingestion 30-90 minutes • transdermal (topical) variable (minutes to hours)

  35. Aspects of Drug Pharmacokinetics (ADME) Drug at site of administration Absorption Drug in plasma Distribution Drug/metabolites in tissues Metabolism Elimination Drug/metabolites in urine, feces, bile

  36. Absorption • Definition : The process of movement of unchanged drug from the site of administration to systemic circulation. • The ultimate goal is to have the drug reach the site of action in a concentration which produces a pharmacological effect. • No matter how the drug is given (other than IV) it must pass through a number of biological membranes before it reaches the site of action.

  37. LIPID BILAYER KLECOP, Nipani

  38. DIFFUSION THROUGH MEMBRANES the Rate dependent on polarity and size. • Polarity estimates partition coefficient. • The greater the lipid solubility – the faster the rate of diffusion • Smaller molecules penetrate more rapidly. • Highly permeable to O2, CO2, NO and H2O . • Large polar molecules – sugar, amino acids, phosphorylated intermediates – poor permeability • These are essential for cell function – must be actively transported

  39. MOVEMENT OF SUBSTANCES ACROSS CELL MEMBRANES KLECOP, Niani

  40. MECHANISMs OF DRUG ABSORPTION • Passive diffusion • Carrier- mediated transport a) Facilitated diffusion b) Active transport • PINOCYTOSIS KLECOP, Nipani

  41. PASSIVE DIFFUSION Also known as non-ionic diffusion. It depends on the difference in the drug concentration on either side of the membrane. Absorption of 90% of drugs. The driving force for this process is the concentration or electrochemical gradient.

  42. 2) CARRIER MEDIATED TRANSPORT MECHANISM • Involves a carrier (a component of the membrane) which binds reversibly with the solute molecules to be transported to yield the carrier solute complex which transverses across the membrane to the other side where it dissociates to yield the solute molecule • The carrier then returns to its original site to accept a fresh molecule of solute. • There are two types of carrier mediated transport system: a) facilitated diffusion b) active transport

  43. a)Facilitated diffusion This mechanism driving force is concentration gradient. In this system, no use of energy is involved (down-hill transport), therefore the process is not inhibited by metabolic poisons that interfere with energy production.

  44. b) Active transport More important process than facilitated diffusion. The driving force is against the concentration gradient or uphill transport. Since the process is uphill, energy is required in the work done by the barrier. As the process requires energy, it can be inhibited by metabolic poisons that interfere with energy production.

  45. Drug AbsorptionActive vs. Passive • Active transport: • Carrier-mediated • Energy-dependent • Against conc gradient • Shows carrier saturation kinetics • Passive transport • Energy-independent • No carrier involved • Along conc gradient • No saturation kinetics ATP Carrier-mediated energy-dependent active transport ADP + Pi Passive diffusion of a water-sol drug via aqueous channel AH B Passive diffusion of a lipid-sol drug A- BH+

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