Revision

• Lipophillic drugs?


  fat soluble drugs that can pass easily across cell membrane. they can move across the gut wall and so are often given orally as they can be easily taken up by the GI tract.
• Hydrophillic drugs?


  These readily dissolve in solution as they are ionised. They cannot pass across the cell membrane readily and require an active transport process to do this. They are usually given parenterally by injection.
• Topical?


  Drugs are administered on the surface of the body or its mucous membranes, some will remain in the area applied whilst others will be absorbed across the topical surface and diffuse into plasma.
• Inhaled?


  drugs are administered via a gaseous carrier or inhaler and the animal breathes in the drug. these drugs then pass from the alveoli of the lungs in the blood stream.
• Oral?


  drugs administered into the animals mouth and drug is ingested.
• Parenteral?


  By injection. 3 main routes iv, im, sc.
• Absorption?


  Process by which drugs are taken up into the body from the site of administration.
• Oral absorption- non-selective (passive)?


  Absorption which occurs by the movement of the molecules from an area of high concentration (SI) into area of low concentration (BS), where it enters the hepatic portal circulation and into the plasma.
• the less lipid soluble the drug- what affect does it have on absorption?


  Slower absorption as they have to pass across the lipid cell membrane.
• Step 1: movement of drugs from S/C injection?

  drug moves from interstitial spaces of the s/c tissues.
• Step 2: s/c movement


  diffuses into the plasma of the blood supply to the area. Once in plasma it is distributed around the body

  
• Step 3: s/c movement?


  It leaves the plasma, re-entering into the interstitial fluid
• Step 4: s/c movement?


  then entering the intracellular fluid when it reaches the target cell/tissue.
• Factors affecting absorption?


  Tissue perfusion and GIT factors.
• Absorption- what are GIT factors>


  abnormal gut function can reduce rate of absorption and decrease bioavailability of drugs. Vomiting expels the drug before it reaches the SI for absorption.
• Distribution?


  process by which the drug is delivered to the target cell/tissue via the animals blood stream.
• factors affecting distribution?


  Protein binding, tissue perfusion, formulation of the drug, BBB
• Distribution- protein binding (free drugs)?

  Free drugs move by diffusion from the blood stream into tissue quickly as nothing is preventing their movement.
• Distribution- protein binding (protein bound)?


  Bound drugs remain in the plasma until the protein releases them, this occurs when the concentration of free drug in the plasma falls.
• distribution- drug fromulation?


  lipophilic drugs can cross cell membrane easily. Hydrophilic drugs can pass through gaps between cells in the capillary wall.
• Distribution- BBB?


  Lipid soluble drugs can pass across the BBB more readily so they are distributed more effectively to the CNS.
• Agonist?


  Drugs fully bind the cell receptors and in doing so can cause a specific biochemical effect. they are perfect fit for the receptors.
• Antagonist?


  drugs reduce or prevent cell receptor activation so they can can combine with the receptor but are not an exact fit. Block receptors so agonist drugs cannot access receptors.
• Non-specific drugs?


  Drugs can bind to large number of different receptors so cause wider range of effects.
• Specific drugs?


  Will bind to a specific receptor/s. Allows the drug to have its desired effect on the specific receptors without having adverse effects on others.
• Up-regulation of receptors?


  Makes animals more sensitive to the drug. Cell receptors increases or present ones becomes more sensitive to the drug when continually exposed to antagonist. Lower doses to have same effect.
• Down-regulation?


  animal is less sensitive to the drug effect of the drug. Cell receptors exposed to agonist decrease in numbers or may become tolerant. Higher doses to achieve same effect.
• Half-life?


  time it takes for the concentration of the drug in the blood stream to decrease by half through metabolism and elimination.
• What does half-life determine?


  When repeat dosing will be required to maintain therapeutic levels.
• Therapeutic index?


  Indicator of safety of drug, drug with high TI are safest.
• Affinity?


  Measures how well a drug binds to a receptor.
• Efficacy?


  Ability of the drug to initiate a response once bound to a receptor.
• High efficacy?


  are more efficient at causing an effect. Strong attraction and binding.
• Potency?


  Has high affinity and efficacy.
• Adverse reactions?


  drug causes an undesirable effect, some may be mild whist other may be fatal.
• Examples of adverse reaction?


  Oral drugs which irritate GI tract, some drugs unsuitable for I/M or I/V route, I/V route can cause anaphylactic reaction.
• 2 ways kidneys excrete drugs?

  Glomerular filtration and tubular secretions.
• excretion- glomerular filtration?


  Glomerulus in kidneys filter drug molecules out of the blood into glomerular filtrate, which is then eliminated as urine.
• Excretion- tubular secretion?


  kidney tubule cells secrete metabolites out of the capillaries surrounding the tubule and into the glomerular filtrate, which then becomes urine.
• First pass effect?


  drugs are transported directly to the liver before they are distributed around the body.