Term
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Definition
| movement of a drug through the body, how the body affects the drug. |
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Term
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Definition
| Mechanism of action leading to the therapeutic and toxic effects of the drug, how the drug affects the body. |
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Term
| List and describe the 4 components of pharmacokinetics. |
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Definition
Absorption-rate and transfer of the drug from the site of administration to the blood. ***bioavailability***-the percentage or fraction of the administered dose which reaches the systemic circulation. The higher the bioavailability, the more drug is absorbed.
Distribution-the transportation of a drug from the bloodstream to various tissues in the body.
Metabolism-the chemical inactivation of a drug, primarily occurs in the liver
Elimination-the process by which drugs and their metabolites are removed from the body. The kidney is the main organ involved, liver second. |
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Term
| List and describe the factors that affect absorption. |
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Definition
1. Drug characteristics
A. bioavailability
B. drug concentration
C. Lipophilic drugs formulations-nonionized medications are more lipid soluable and more readily absorbed.
D. Acidity of the medication
2. Routes of administration
First pass effect-
3. Blood flow
4. Cell membranes
Passive vs active transport of medication across cell membranes. |
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Term
| generic drug should have a bioavailability within what range of the brand name drug? |
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Definition
| between 80 and 125% of the brand name drug. |
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Term
| Explain the concept of Volume of Distribution. |
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Definition
| The size of a compartment necessary to account for the total amount of drug in the body if it were present throughout the body at the same concentration found in the plasma. The total area to which a drug is distributed. Influenced by lipid vs water solubility of drug and plasma and tissue protein binding properties of the drug. |
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Term
A patient is started on a drug that has a half-life of 14 hours, when
would you expect steady-state to be reached? |
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Definition
| 56-70 hours Steady-state is achieved in 4-5 half-lives |
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Term
| Which routes of administration have less of a first-pass effect? |
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Definition
| IV/IM, sublingual, inhalation, rectal, topical |
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Term
Describe some pharmacokinetic differences in pediatric patients
compared to adult patients |
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Definition
Absorption-related: decreased gastric acidity, gastric emptying time, GI
motility, pancreatic enzyme activity, increased GI surface area, and
increased skin permeability (esp. in premature neonates)
Distribution-related: increased water to lipid ratio, decrease in blood
brain barrier, decrease in plasma proteins
Metabolism-related: decreased liver function through infancy then
somewhat increased in children compared to adults
Elimination-related: decreased renal blood flow, decreased glomerular
filtration, decreased tubular function |
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Term
Describe pharmacokinetic differences in geriatric patients compared
to younger adult patients. |
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Definition
Altered GI tract functioning:
Delayed gastric emptying
↓ gastric acidity
↓ splanchnic blood flow
↓ number of gastric mucosal cells
Effects of above on absorption:
Extent of drug absorption not usually altered with aging; however rate may decline
↓ gastric acidity may affect absorption of some drugs that require acidic environment for adequate absorption (e.g.ketoconazole, itraconazole)
Body composition changes:
↓ total body water
↓ lean body mass
↑ body fat
↓ creatinine production
↓ albumin
↑ alpha-1-acid glycoprotein
Effects the above can have on drug distribution:
Lipophilic drugs- prolonged effect (e.g. diazepam)
Hydrophilic drugs-higher peak concentrations (e.g. aminoglycosides)
Protein bound to albumin-↑ unbound drug and greater effect (e.g. phenytoin)
Protein bound to AAG (alpha-1-acid glycoprotein)-↓ unbound drug and decreased effect (e.g. lidocaine)
Changes that can effect drug metabolism or elimination:
↓ hepatic blood flow
↓ in phase I reactions (e.g. oxidation)
No change in phase II reactions (e.g. glucuronidation)
↓ number of nephrons
↓ renal blood flow
↓ glomerular filtration and tubular secretion rate
Approximate 10% decline in creatinine clearance per decade of life after the age of 40 |
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