Pharmacology session 1:

Pharmacokinetics and Pharmacodynamics

 

session 1

 

Albumin is a protein that usually binds medications

Protein binding – when a drug is binding a protein is in the reservoir.

  • drugs that cannot bind are “free” and can be absorbed
  • Starving people will have fewer circulating protein and cause there to be more than usual amount of the drug to be free creating a toxic environment.
  • only the free drug is metabolized

 

Prodrug: a form of a drug given that are converted to the active drug by the body.

 

CYP 450 Cytochrome enzyme system

  • 12 channels
  • 90% of drugs go through 6 of them
  • competition for channels occurs when multiple drugs are used
  • drugs can turn on and of the channel
    • inducers
    • inhibitors
  • Induction – liver produces more enzymes and makes the drug breakdown quicker

 

generic drug

  • Dose can be 80-120% of drug
  • The distribution of the drug may not be half and half on the score

 

Weight of a drug (gm or mg)is not an end all for the response compared to a different drug, they are not related.

 

ED 50 – effective dose for 50% of population

LD 50 – lethal for 50% of the population

TI = LD/ED – therapeutic index closer to 1 = a more dangerous dose

 

Dosing schedule – we are looking for a schedule that is often enough to produce the desired effect without being toxic.

  • Plateau: this is what we are looking for in a dosing schedule drug. It may take 4-5 half lives(also doses) before this plateau occurs.

 

Peak level is the highest plasma level of the drug about 1-2 hours after oral, and 30 mins after IV.

Trough level is 10-15 mins before a dose when the plasma drug level is the lowest

 

Most drugs need to be taken with a full glass of water to help the pilll dissolve, and before meals.

 

If a pt has kidney failure excretion can take 25 hours as opposed to 1.5 hours in a pt with healthy kidneys.

 

Side Effects

    • secondary predictable known effect from a drug

 

  • Mild, tolerable!

 

    • ie. nausea, GI issues, dry mouth, dizziness

Adverse reaction  

 

  • severe!

 

  • unexpected response to a drug, and can be very intense
  • can be permanent, cause many other health issues including death
  • often occurs in the young and old

 

Elderly

  • renal function test is creatinine clearance
  • high gastric pH can cause bad  absorption
  • narrow therapeutic index.

 

Toxicity

  • excessive dose
  • causes adverse reactions
  • DNA can make a person more or less susceptible

 

Idiosyncratic effect

  • Genetics causing an uncommon response to a drug

 

Iatrogenic Disease

  • A physician produced the disease

 

Teratogenic effect

  • to make a birth defect from a medication.

 

medications that require close attention – Anticoagulants, Nephrotoxic drugs, Antiepileptic, digoxin.

 

Allergies and nursing responsibility

  • ask pt and family
  • document
  • allergy bracelet
  • stop drug if reaction occurs
  • notify provider, stay at bedside
  • ready emergency equipment
  • monitor during administration of antihypersensitivity agent

 

Drug to drug interactions

  • potentiation: drugs in same class or acting on the same system can add up in there effects.
    • sedatives + alcohol = SEDATION , coumadin + aspirin = bleeding
  • interference: action on the 450 enzyme system on drug speeds up or slows down the metabolism or excretion of another drug.
    • erythromycin + digoxin = increased serum levels of digoxin
    • +coumadin = increased action of coumadin
  • Displacement: two drugs, one receptor.
  • Antagonism: one drug cases the decreases the action of another
  • food can affect a drug action
    • vit K reduces anticoagulants
    • tetracycline and milk causes the drug not to not to be absorbed
    • Grapefruit + CCblockers will increase drug effects
    • Acidic food increases absorption of Fe
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