Pharmacokinetics and Pharmacodynamics
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
- Induction – liver produces more enzymes and makes the drug breakdown quicker
- 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.
- secondary predictable known effect from a drug
- Mild, tolerable!
- ie. nausea, GI issues, dry mouth, dizziness
- 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
- renal function test is creatinine clearance
- high gastric pH can cause bad absorption
- narrow therapeutic index.
- excessive dose
- causes adverse reactions
- DNA can make a person more or less susceptible
- Genetics causing an uncommon response to a drug
- A physician produced the disease
- 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
- 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