NURS 8024 PHARM EXAM 1
2 Major drug administration routes - ANSWERS-Enteral
Parenteral
Enteral Drug Administration - ANSWERS-Easily self-administered,
• Drug absorption pathways complicated
• First-pass metabolism can limit the
amount of drug that enters systemic
circulation
• Influenced by food and other drugs
Parenteral Drug Administration - ANSWERS-• Intravenous, intramuscular and
subcutaneous
• More control over actual dose of drug
• Direct into systemic circulation
•
→ Bypasses first-pass effect and harsh GI environment
• Can be used for drugs poorly absorbed GI
• Rapid onset of action
Disadvantages of parenteral drug administration - ANSWERS--Can't take it back
,- infection risk
Other routes of administration - ANSWERS-• Inhalation
• Rapid delivery, large surface area - (good for gases, aerosols, respiratory drugs)
• Nasal
• Intrathecal/intraventricular
• Topical
• Transdermal
• Rectal - 50% of circulatory drainage bypasses portal circulation
Drug transport Mechanisms - ANSWERS-passive diffusion, facilitated diffusion,
active transport
Drug absorption - ANSWERS-• Drugs are typically weak acids or weak bases
• Acidic drugs release a Hᶧ causing a charged anion to form
• Drug passes readily when uncharged
Role of size and molecular weight in drug absorption - ANSWERS-• Drugs can vary
in size from MW of 7 (lithium) to 50,000
(thrombolytic enzymes)
• Most drugs have molecular weight from 100-1000
• Smaller size
,→ easier to cross membranes
Concentration of a drug depends on - ANSWERS-• pH of the drug
• compartment site
• pka of drug
pKa of a drug - ANSWERS-the pH of a solution when 50% of the drug is ionized
Factors in Absorption and Distribution - ANSWERS-Chemical properties
• Solubility
Hydrophilic (lipophobic)
Lipophilic (hydrophobic)
• Chemical nature - pH and pKa
• Molecular weight
• Partition coefficient
Lipid Barriers - ANSWERS-separate aqueous compartments in the body
Lipid:aqueous partition coefficient
pKa - ANSWERS-the pH at which the concentrations of the ionized and
non-ionized forms are equal
, Partition Coefficient - ANSWERS-• ratio of lipid solubility to aqueous solubility
• the higher the partition coefficient, the more membrane soluble
is the substance
Factors influencing GI Absorption - ANSWERS-• Blood flow- Intestinal blood flow >
stomach blood flow
• pH - especially w/ H2 receptor blocker or proton pump inhibitor (PPI)
• Intestinal surface area (microvilli) (1000x more than stomach)
• Contact time with absorptive surface- Variables
• Rapid vs slow GI transport
• Parasympathetic input -
↑ rate of gastric emptying
• Sympathetic input
→ delayed gastric emptying
• Food
→ delayed absorption
Bioavailability - ANSWERS-Fraction of chemically unchanged drug that
reaches systemic circulation
Factors influencing bioavailability - ANSWERS-• First pass metabolism
• Solubility
2 Major drug administration routes - ANSWERS-Enteral
Parenteral
Enteral Drug Administration - ANSWERS-Easily self-administered,
• Drug absorption pathways complicated
• First-pass metabolism can limit the
amount of drug that enters systemic
circulation
• Influenced by food and other drugs
Parenteral Drug Administration - ANSWERS-• Intravenous, intramuscular and
subcutaneous
• More control over actual dose of drug
• Direct into systemic circulation
•
→ Bypasses first-pass effect and harsh GI environment
• Can be used for drugs poorly absorbed GI
• Rapid onset of action
Disadvantages of parenteral drug administration - ANSWERS--Can't take it back
,- infection risk
Other routes of administration - ANSWERS-• Inhalation
• Rapid delivery, large surface area - (good for gases, aerosols, respiratory drugs)
• Nasal
• Intrathecal/intraventricular
• Topical
• Transdermal
• Rectal - 50% of circulatory drainage bypasses portal circulation
Drug transport Mechanisms - ANSWERS-passive diffusion, facilitated diffusion,
active transport
Drug absorption - ANSWERS-• Drugs are typically weak acids or weak bases
• Acidic drugs release a Hᶧ causing a charged anion to form
• Drug passes readily when uncharged
Role of size and molecular weight in drug absorption - ANSWERS-• Drugs can vary
in size from MW of 7 (lithium) to 50,000
(thrombolytic enzymes)
• Most drugs have molecular weight from 100-1000
• Smaller size
,→ easier to cross membranes
Concentration of a drug depends on - ANSWERS-• pH of the drug
• compartment site
• pka of drug
pKa of a drug - ANSWERS-the pH of a solution when 50% of the drug is ionized
Factors in Absorption and Distribution - ANSWERS-Chemical properties
• Solubility
Hydrophilic (lipophobic)
Lipophilic (hydrophobic)
• Chemical nature - pH and pKa
• Molecular weight
• Partition coefficient
Lipid Barriers - ANSWERS-separate aqueous compartments in the body
Lipid:aqueous partition coefficient
pKa - ANSWERS-the pH at which the concentrations of the ionized and
non-ionized forms are equal
, Partition Coefficient - ANSWERS-• ratio of lipid solubility to aqueous solubility
• the higher the partition coefficient, the more membrane soluble
is the substance
Factors influencing GI Absorption - ANSWERS-• Blood flow- Intestinal blood flow >
stomach blood flow
• pH - especially w/ H2 receptor blocker or proton pump inhibitor (PPI)
• Intestinal surface area (microvilli) (1000x more than stomach)
• Contact time with absorptive surface- Variables
• Rapid vs slow GI transport
• Parasympathetic input -
↑ rate of gastric emptying
• Sympathetic input
→ delayed gastric emptying
• Food
→ delayed absorption
Bioavailability - ANSWERS-Fraction of chemically unchanged drug that
reaches systemic circulation
Factors influencing bioavailability - ANSWERS-• First pass metabolism
• Solubility
