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Tutorial 1

Tutorial 1. January 18, 2013. Contact Details. Two TAs Julian Chesterman julian.chesterman@chee.queensu.ca Biosciences 1424 Cody Brown c.brown @ queensu.ca HMRC 5- 201. Quick Overview of Course to Date. Definition of drug/objectives of drug dosage formulation

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Tutorial 1

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  1. Tutorial 1 January 18, 2013

  2. Contact Details • Two TAs • Julian Chestermanjulian.chesterman@chee.queensu.caBiosciences 1424 • Cody Brown c.brown@queensu.ca HMRC 5-201

  3. Quick Overview of Course to Date • Definition of drug/objectives of drug dosage formulation • Drug - substance or mixture of substances advertised for treatment or prevention of disease or symptoms, e.g. Aspirin • Drug dosage – include excipients to facilitate/control delivery of drug, protect drug from degradation, conceal taste/odor • Want predictable and repeatable therapeutic response

  4. Time after Administration Key Definitions • Bioavailability: extent of absorption and the rate at which an administered dose reaches systemic circulation in its active form • Therapeutic Window: Minimum Toxic Concentration Plasma Concentration (Cp) Minimum Effective Concentration

  5. Hepatic First Pass Effect • Everything absorbed in the intestines enters the portal vein and is transported directly to the liver • Liver (poison filter) is responsible for metabolizing chemicals in the blood • Consequently a portion of the drug will be metabolized before it ever reaches systemic circulation

  6. Routes of Administration –Pros/Cons • Oral • Pro: Patient Compliance • Con: Hepatic first-pass effect/Too slow for emergencies • Rectal • Pro: Avoids some hepatic first-pass effect • Con: Low buffering capacity of fluid

  7. Routes of Administration –Pros/Cons • Buccal/Sublingual • Pro: Rapid absorption/no first-pass effect • Con: Bad taste of drugs/small doses • Parenteral (Intravenous/Subcutaneous, etc.) • Pro: 100% available/rapid delivery (emergencies) • Con: Patient compliance (fear of needles/need for training)

  8. Routes of Administration –Pros/Cons • Transdermal • Pro: Convenient/sustained release (good for drugs with narrow therapeutic window or requiring frequent delivery by other methods) • Con: Drug must be potent and effective when delivered slowly • Nasal • Pro: bioavailability similar to injection for some drugs • Con: Formulation complexity/shelf-life

  9. Routes of Administration –Pros/Cons • Pulmonary • Pro: Large surface area and thin membrane • Con: More complex to formulate

  10. Drug Absorption Simple diffusion Because viscosity of the phospholipid bilayer is 100 to 1000 times higher than that of water, movement across cell membranes (hydrophobic region) is the rate-limiting step in drug absorption by simple diffusion (Stokes-Einstein equation). Not all molecules can diffuse across phospholipid bilayer.

  11. Drug Absorption Facilitated Diffusion: Transport across cell membrane via carrier proteins. Transport from high concentration to low concentration. Active Transport: Transport across cell membrane against a concentration gradient . Requires expenditure of energy by cell.

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