Drug Processing

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Drug Processing

• Pharmacokinetics movement of drugs across body
  membranes to reach the target organ
• Absorption
• Distribution
• Metabolism
• Excretion
• Influences the determination of proper dosing
  schedule

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Pharmacokinetics (cont.)

• Absorption
• Movement of a drug from its administration site
  through or across tissue into the systemic
  circulation
• Degree rate of absorption depend on the
  administration route, pt age physical
  condition, potential interactions with other
  drugs or foods
• Degree of absorption also depends on the drugs
  mechanism of absorption (diffusion,
  carrier-mediated diffusion), active transport, or
  pinocytosis

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Pharmacokinetics (cont.)

• Distribution
• Movement of a drug from the systemic circulation
  into the tissue
• May be affected by the BLOOD-BRAIN barrier,
  cardiac output, blood supply to target tissue,
  the degree of vessel constriction or dilation,
  and the degree to which the drug binds to plasma
  proteins such as albumin

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Pharmacokinetics (cont.)

• Metabolism
• Alteration of a drug to a more active or less
  active form, usually in the liver
• May be affected by genetic factors, pts age and
  physical condition, and the drug itself (drugs
  lipid solubility)

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Pharmacokinetics (cont.)

• Excretion
• Elimination of a drug from the circulation
• Most drugs are excreted by the kidneys into the
  urine into the bile, then the feces by the
  lungs into the air or into the breast milk

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Pharmacokinetics (cont.)

• Dosing schedule
• Onset of Action the time when a drugs effects
  first become noticeable
• Peak Concentration Level the maximum blood
  concentration level achieved through absorption
  at this level most of the drug reaches the site
  of action provides therapeutic effect
• Duration of Action length of time a drug acts
  on the body
• Half-life the time required for a drugs plasma
  concentration to decrease by 50

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(DP) Pharmacodynamics

• Mechanism by which specific drugs produce
  biochemical and physiologic changes in the body
• Pharmacodynamic Events
• A given drug interacts with specific receptor
  site
• It causes general interaction with cell
  metabolism
• The cellular environment function are altered
  to produce the desired effect

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(DP) Pharmacodynamics

• Therapeutic effect
• Refers to a drugs ability to produce a desired
  effect
• Factors affecting response to a drug includes
  body weight, size, gender, route, medical
  condition psychological factors
• Some drugs must be taken on an empty stomach to
  achieve an optimal effect. Other drugs should be
  taken with food.

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(DP) Pharmacodynamics

• Adverse Drug Reaction
• Undesired drug effects
• Mild, severe or live threatening
• May occur after the first dose, several doses, or
  many doses
• Some drugs are known to produce some adverse
  reactions Ca drugs are highly toxic
• Adverse reactions often are unpredictable

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(DP) Pharmacodynamics

• Allergic reaction hypersensitivity reaction
• May occur with minutes after the drug is given or
  may be delayed for hours or days

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(DP) Pharmacodynamics

• Anaphylactic Shock an extremely serious
  allergic reaction that usually occurs immediately
  after the administration of the drug
• Signs Symptoms
• Respiratory Bronchospasm, dyspnea, wheezing,
  cough
• Cardiovascular Extremely low BP, tachycardia,
  syncope, cardiac arrest
• Integumentary Urticaria, Pruritis, Sweating
• GI Nausea, vomiting, abdominal pain

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(DP) Pharmacodynamics

• Teratogenic Effect drugs given to a mother that
  causes developmental physical defects in a fetus

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(DP) Pharmacodynamics

• Drug Idiosyncrasy is unusual or unexpected
  response to a drug (Benadryl may cause
  hyperexcitability in children, or pt may receive
  hypnotic for sleep, but remain awake and
  experience nervousness or excitement)

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(DP) Pharmacodynamics

• Drug Tolerance is used to describe a decreased
  response to the dose of a drug, usually requiring
  an increase in dosage to give the desired effect
  (may develop when narcotics tranquilizers are
  taken for a long time)

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(DP) Pharmacodynamics

• Cumulative Drug Effect may be seen in those with
  liver kidney disease. The body becomes unable
  to metabolize excrete one (normal) dose of a
  drug before the next dose is given

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(DP) Pharmacodynamics

• Loading Dose refers to administration of one or
  more doses at the onset of therapy to quickly
  reach the therapeutic blood level thereby
  hasten a therapeutic effect commonly the loading
  dose is larger than the maintenance dose

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(DP) Pharmacodynamics

• Minimum Dose smallest amount of drug that will
  produce therapeutic result
• Maximum Dose largest amount of a drug that will
  produce a desired effect without producing
  symptoms of toxicity

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(DP) Pharmacodynamics

• Maintenance Dose required to keep the drug-blood
  level at a steady state in order to maintain the
  desired effect

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(DP) Pharmacodynamics

• Drug Efficacy refers to a drugs maximal
  effectiveness
• Measures of drugs efficacy include vital signs,
  body weight, and easing of symptoms that the drug
  is expected to relieve
• Therapeutic Drug Levels may be monitored to
  individualize drug dosage, to evaluate toxicity
  to monitor compliance

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(DP) Pharmacodynamics

• Drug Interaction
• Drug-Drug Interaction occurs when one drug
  interacts with or interferes with the action of
  another drug
• Drugs known to cause interactions include oral
  anticoagulants, oral hypoglycemics,
  antiinfectives, antiarrhythmics, cardiac
  glycosides alcohol

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(DP) Pharmacodynamics

• Additive Drug Reaction
• when the combined effect of two drugs is equal to
  the sum of each drug given alone (heparin
  alcohol will increase bleeding, 112)
• Synergistic Reaction
• when two drugs interact with each other produce
  an effect that is greater than the sum or their
  separate action (person taking hypnotic takes
  also alcohol will experience effect that is
  greater than if either of two agents were taken
  alone)
• Antagonistic Reaction
• when one drug interferes with the action of
  another, causing a neutralization or decrease in
  the effect of one of the drugs (Heparin/protamine
  sulfate MS/Narcan Coumadin/Aquamephytoin

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(DP) Pharmacodynamics

• Drug-Food Interaction when a drug is taken on an
  empty stomach it is absorbed at a faster rate
  then when taken with food in the stomach
• Toxic Reactions drugs are capable of producing
  toxic or poisonous reaction if administered in
  large dosage or when blood concentration levels
  exceed the therapeutic level. Some toxic effects
  are immediately visible others may not be
  evident for weeks or months

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(DP) Pharmacodynamics

• Factors influencing drug response
• Age (infants elderly may require smaller
  dosage) the practice of polypharmacy may lead to
  an increase in the number of adverse reactions
• Weight in general, dosages are based on a weight
  of approx 70 kg
• Gender women may require a smaller dose of some
  meds (different body fat water ratio than men)
• Route of Administration IV, IM, SQ, PO (antacids
  are given only orally)

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(DP) Pharmacodynamics

• Common Responses to Medications
• Desired effect the drug does what it is supposed
  to do (temp reduction after taking aspirin)
• Side effect mild, but annoying responses to meds
  (gastric burning caused by aspirin)
• Adverse effects more severe symptoms or problems
  (severe gastric bleeding from an ulcer caused by
  aspirin)

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(DP) Pharmacodynamics

• Idiosyncratic response strange, unique, or
  unpredicted reactions (blood in the urine caused
  by aspiring rare event)
• Allergic Response antigen-antibody reaction
  hives, rashes, itching, or swelling of skin
  rash or SOB occasionally seen in pts allergic to
  aspirin
• Anaphylactic Response severe form of allergic
  reaction that is life threatening severe SOB,
  apnea, or cardiac collapse

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