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Questions and Answers
What is an important factor affecting drug absorption?
What is an important factor affecting drug absorption?
- Age
- Pregnancy
- Inflammation
- All of the above (correct)
Where are acidic drugs absorbed?
Where are acidic drugs absorbed?
- Intestines
- Liver
- Kidneys
- Stomach (correct)
What can alter the absorption rate of a drug?
What can alter the absorption rate of a drug?
- Changes in pH
- Co-administered drugs
- Changes in intestinal motility
- All of the above (correct)
What is the primary elimination route for polar drugs?
What is the primary elimination route for polar drugs?
What determines the distribution of a drug in the body?
What determines the distribution of a drug in the body?
What is the volume of distribution (Vd) of a drug?
What is the volume of distribution (Vd) of a drug?
Why do drugs with low Vd remain mostly in the plasma?
Why do drugs with low Vd remain mostly in the plasma?
What is the significance of a high Vd for a drug?
What is the significance of a high Vd for a drug?
What is the main purpose of Therapeutic Drug Monitoring (TDM)?
What is the main purpose of Therapeutic Drug Monitoring (TDM)?
What factor influences drug absorption through the GI tract?
What factor influences drug absorption through the GI tract?
Which of the following mechanisms is involved in drug absorption through the GI tract?
Which of the following mechanisms is involved in drug absorption through the GI tract?
What is the most common route of administration for drugs?
What is the most common route of administration for drugs?
What affects the diffusion of a drug from the GI tract to the bloodstream?
What affects the diffusion of a drug from the GI tract to the bloodstream?
What is the primary mechanism of drug absorption through the GI tract?
What is the primary mechanism of drug absorption through the GI tract?
Which of the following factors does not influence drug absorption through the GI tract?
Which of the following factors does not influence drug absorption through the GI tract?
What determines the rate of absorption of a drug through the GI tract?
What determines the rate of absorption of a drug through the GI tract?
What is the characteristic of a drug with a high volume of distribution?
What is the characteristic of a drug with a high volume of distribution?
What is the effect of hepatic dysfunction on the drug Carbamazepine?
What is the effect of hepatic dysfunction on the drug Carbamazepine?
What is the most serious side effect of Carbamazepine?
What is the most serious side effect of Carbamazepine?
What is the plasma concentration of Carbamazepine associated with hematologic dyscrasias and possible aplastic anemia?
What is the plasma concentration of Carbamazepine associated with hematologic dyscrasias and possible aplastic anemia?
What is the characteristic of Ethosuximide?
What is the characteristic of Ethosuximide?
What is the therapeutic index of Lithium?
What is the therapeutic index of Lithium?
What is the characteristic of Tricyclic Antidepressants (TCAs)?
What is the characteristic of Tricyclic Antidepressants (TCAs)?
What is the effect of high plasma concentration on the toxicity of Ethosuximide?
What is the effect of high plasma concentration on the toxicity of Ethosuximide?
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Study Notes
Drug Absorption and Distribution
- Acidic drugs are absorbed in the stomach, while basic drugs are absorbed in the intestines due to the pH differences
- Many factors can alter absorption rates, including changes in intestinal motility, pH, inflammation, food, and co-administered drugs
- Genetic variations, age, pregnancy, and pathologic conditions can also affect absorption
Drug Distribution
- Hydrophobic (lipid-soluble) drugs can easily traverse cellular membranes and partition into lipid compartments
- Polar but non-ionized drugs can cross cell membranes but do not sequester into lipid compartments
- Ionized drugs diffuse out of the vasculature at a slow rate
- Polar (water-soluble) drugs are primarily eliminated by the kidneys, while nonpolar (lipid-soluble) drugs are eliminated in feces and bile
Volume of Distribution (Vd)
- Vd is an index that describes a drug's distribution characteristics
- Vd is calculated as Vd = D/C, where D is the IV injected dose and C is the concentration in plasma
- Drugs with low Vd are contained mostly in the plasma due to being ionized and highly water-soluble or highly protein-bound
- Drugs with high Vd are mostly in tissues due to being hydrophobic and lipid-soluble
Therapeutic Drug Monitoring (TDM)
- Definition: analysis, assessment, and evaluation of circulating concentrations of drugs in serum, plasma, or whole blood
- Major purposes of TDM: ensure dosage produces maximal therapeutic benefit and identify when the drug is outside the therapeutic range
Routes of Administration
- Intravenous (IV): injected directly into circulation
- Intramuscular (IM): injected into muscle
- Subcutaneous (SC): injected just under the skin
- Transcutaneous: inhaled or absorbed through the skin
- Suppository: rectal delivery
- Oral Administration: by mouth
Factors Influencing Drug Levels
- Route of Administration
- Rate of Absorption
- Distribution of drug within the body
- Rate of Elimination
Antiepileptic and Psychoactive Drugs
- Carbamazepine (Tegretol): treats various seizure disorders, but has serious toxic adverse effects
- Ethosuximide (Zarontin): controls petit mal seizure, with rare and tolerable toxicities associated with high plasma concentrations
- Lithium: treats manic depression, with a narrow therapeutic index and determination of serum lithium levels done by ion-selective electrode
- Tricyclic Antidepressants (TCAs): treat depression and insomnia, with high protein binding and dose-dependent toxicity
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