Pharmacokinetics Flashcards
The movement of drugs in the body.
Pharmacokinetics
Absorption, distribution, metabolism, and excretion.
What are the advantages to absorption with the IV route?
No barriers to absorption. Rapid onset, control, use of large fluid volumes, use of irritant drugs
What are the disadvantages to absorption with the IV route?
High costs, difficulty, and inconvenience. Irreversibility, fluid overload, infection, embolism.
What are the influencing factors on the rate of absorption?
Rate of dissolution, surface area, blood flow, lipid solubility
Absorption IM and subcutaneous routes?
No significant barrier to absorption. Factors affecting the rate of absorption include water solubility (quick absorption) and blood flow to the site of the injection
What are the advantages of absorption injections?
Drugs that do not dissolve completely. Drugs to be absorbed over a long period of time.
What are the disadvantages of absorption injections?
Patient feels pain with each dose. Takes time and skill to avoid injury.
Absorption oral route?
Barriers to absorption include the lining of the stomach. Factors that influence it are the solubility and stability of the drug, gastric and intestinal pH, gastric emptying time, food in the gut, co-administration of other drugs, special coatings on the drug preparation.
Advantages of the absorption via the oral route?
Easy, convient, and no added costs. Oral medications may be retrieved if needed (inducing emesis, catharsis. Preventing absorption in to the blood stream)
Disadvantages of the absorption via the oral route?
Variability, inactivation, patient requirements, local irritation
Absorption- drug forms for oral route?
Chemical equivalence Bioavailability Difference in tablets Enteric coated tablets Sustained release capsules
Absorption- additional routes of administration other than injection, IV, oral?
Topical (applied to surfaces for local therapy)
Transdermal (through the skin)
Inhaled
Rectal and vaginal suppository
Direct injection into specific site (intracardiac, intraarticular, intrathecal)
Major factors that affect drug distribution?
Blood flow to the tissues
Ability of the drug to exit the vascular system (blood brain barrier, placenta, protein binding like albumin)
Ability of drugs to enter cells
Also known as biotransformation. Occurs in the liver. Special considerations?
Metabolism.
First Pass Effect, age, nutritional status
Possible consequences of metabolism?
Accelerated renal excretion of drugs, drug activation, increased therapeutic action, activation of “prodrugs,” increased toxicity, decreased toxicity
Excretion, what are ways drugs and metabolites exit the body?
Urine, bile, sweat, saliva, breast milk, expired air
Time it takes for a drug to elicit a therapeutic response.
Time it takes for the drug to reach its maximum therapeutic response.
Time that drug concentration is sufficient to elicit a therapeutic response.
Onset
Peak
Duration
Medication goes from the site of administration to the blood
Medication goes from blood flow to the tissues
Absorption
Distribution
The drug’s lowest plasma level
Trough concentration
When a drug has a narrow therapeutic range, measuring the peak and trough concentrations can assist in what?
Ordering doses of the drug that will keep the plasma levels between the minimum effective concentration (MEC) and the toxic concentration.
For drugs whose half lives are long, achieving plateau?
Could take days or weeks. When plateau must be achieved quickly, a large initial dose can be administered. This large initial dose is called a loading dose.
After high drug levels have been established with a loading dose?
Plateau can be maintained by giving smaller doses. These smaller doses are referred to as maintenance doses.
When a drug is discontinued how much of the drug will be eliminated from the body?
Most (94%) of the drug in the body will be eliminated over an interval equal to about four half-lives.
