Pharmacology 2060A/B Lecture Notes - Lecture 2: Subcutaneous Tissue, Drug Metabolism, Sublingual Administration
11 Apr 2016
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Pharm Module 2 – Pharmacokinetics – Absorption
Pharmacokinetics: the study of drug movement in the body
• What the body does to the drug
• Composed for 4 basic processes:
1. Absorption
2. Distribution
3. Metabolism
4. Excretion
Absorption: the movement of the drug from the site of administration into the blood
• Rate of absorption determine how quickly the drug effect will occur
• Amount of drug absorption determines how intense the effect of the drug will be
Factors Affecting Absorption
1. Rate of Dissolution: dissolving in solution, drugs must dissolve before they can
be absorbed
• Drugs with a fast rate of dissolution will have a faster onset of action than
drugs with slow dissolution
2. Surface area: major determinant of drug absorption, the larger the surface area,
the faster the drug absorption. The intestine has thousands of finger-like
projections called villi, which make the surface area very large.
3. Blood flow: absorption is fastest in areas of high BF, high BF maintains a
concentration gradient which drives absorption. Exercise increases BF to certain
tissue such as muscle and can increase drug absorption. BF is decreased in
heart failure, severe hypotension, hypothermia, and circulatory shock.
4. Lipid solubility: drugs with high lipid solubility (lipophilic drugs) are absorbed
more rapidly that water soluble (hydrophilic) drugs. Lipophilic drugs are able to
cross cell membrane whereas hydrophilic drugs cannot directly penetrate the
membrane.
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5. pH Partitioning: drug absorption is greater where there’s a difference between
the pH at the site of administration and the blood, such that the drug is ionized in
the blood. Remember the effect of pH dependant ionization from module 1.
6. Activity of drug transport proteins: the rate and extent of drug absorption can
be significantly impacted by drug transporters. Uptake drug transporters increase
the absorption of drugs. Efflux drug transporters decrease the absorption of
drugs.
find more resources at oneclass.com
find more resources at oneclass.com
Route of Administration
1. Oral (PO = per os which is latin for “by mouth”)
2. Sublingual
3. Transdermal
4. Rectal
5. Intravenous
6. Subcutaneous (SubQ or SC)
7. Intramuscular (IM)
8. Pulmonary
• Routes of admin are often referred to as enteral or parenteral
• Enteral – routes of admin that involve the GI tract
• Parenteral – routes of admin that do not involve the GI tract
1. Oral absorption
Intestine vs Stomach
• Intestine has a much larger SA = much faster absorption
• Absorption is greater in intestines rather than stomach
• Drugs that are weak acids should be better absorbed in the acidic enviro of the
stomach because they would non-ionize
o However, the SA of the stomach is small and the stomach is covered in a
thick layer of mucus
o Therefore, the rate of drug absorption in the intestine will be greater than
the stomach, even if the drug is ionized
o Oral absorption is greatest in the intestine
Pharmaceutical Phase
• Occurs after the patient swallows a tablet
• Involves the disintegration of the tablet and the dissolution of the drug
• If the drug does not completely disintegrate or does not go into solution,
absorption is reduced
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pharmacokinetics: the study of drug movement in the body. Pharm module 2 pharmacokinetics absorption: what the body does to the drug, composed for 4 basic processes, absorption, distribution, metabolism, excretion. The intestine has thousands of finger-like projections called villi, which make the surface area very large: blood flow: absorption is fastest in areas of high bf, high bf maintains a concentration gradient which drives absorption. Exercise increases bf to certain tissue such as muscle and can increase drug absorption. Bf is decreased in heart failure, severe hypotension, hypothermia, and circulatory shock: lipid solubility: drugs with high lipid solubility (lipophilic drugs) are absorbed more rapidly that water soluble (hydrophilic) drugs. Remember the effect of ph dependant ionization from module 1: activity of drug transport proteins: the rate and extent of drug absorption can be significantly impacted by drug transporters. Uptake drug transporters increase the absorption of drugs. Efflux drug transporters decrease the absorption of drugs.
