Drug Absorption

Question 1

Oral route: bioavailability and rate of onset

Answer 1

• bio: 0-100%, varies widely

- relatively slow rate of onset

Question 2

Rectal route: bioavailability and rate of onset

Answer 2

• bio: variable but greater than oral

- onset not rapid

Question 3

Siglingual - Buccal route: bioavailability and rate of onset

Answer 3

• bioavailability generally high

- onset of action within minutes

Question 4

intravenous route: bioavailability and rate of onset

Answer 4

• bioavailability 100%

- most rapid onset of action (<5 min)

Question 5

intramuscular route: bioavailability and rate of onset

Answer 5

• ~100% bioavailability

- aqueous solns absorbed rapidly with rapid onset (5-10 min)

Question 6

subq route: bioavailability and rate of onset

Answer 6

~100% bioavail

-slower, constant rate of absorption

Question 7

inhalation route: bioavailability and rate of onset

Answer 7

• bioavail ~100%

- <5 min

Question 8

oral route: advantages and disadvantages:

Answer 8

Adv: slower, sustained and uniform absorption; decreased frequency of administration, maintenance of therapeutic effect overnight, elimination of peaks and troughs in plasma levels
Dis: greater inpt variability in systemic levels obtained and dosage from failure resulting in “dose-dumping” and drug toxicity

Question 9

rectal route: advantages and disadvantages:

Answer 9

Adv: useful when oral route precluded by V, unconsciousness, post-GI surgery, presence of GI irritation or uncooperative patient
Dis: pt acceptance is not high

Question 10

sublingual route: advantages and disadvantages:

Answer 10

Adv: venous drainage from mouth is to the superior vena cava protecting drug from rapid hepatic first pass metabolism plus faster onset of action
• Useful for drugs that are lipid soluble and relatively potent (< 1 mg doses) as there is a smaller surface area for absorption relative to GI tract

Question 11

IV route: advantages and disadvantages:

Answer 11

Adv: Most direct route of administration, Accuracy and immediacy of drug delivery exceeds all other routes, Often used for drugs with narrow therapeutic index
Dis: Bypasses absorption barriers –> can result in introduction of infectious agents, Most hazardous route, easy to reach toxic levels rapidly, reversal of effect often difficult

Question 12

IM route: advantages and disadvantages:

Answer 12

Adv: Can be used if drug too irritating for subcutaneous administration
Dis: pain, tissue necrosis (if high pH), and microbial contamination

Question 13

Subq route: advantages and disadvantages:

Answer 13

Adv: Period of drug absorption can be altered intentionally
Dis: Only for non-irritating drugs, volume of dose is limited

Question 14

Inhalation route: advantages and disadvantages:

Answer 14

Adv: Rapid rate of absorption due to large surface area and high blood flow in pulmonary tissue

Question 15

Transdermal route: advantages and disadvantages:

Answer 15

Adv: 1st pass metabolism is avoided
Dis: Prolonged drug levels can be achieved - potential for unexpected drug accumulation and toxicity, Drug must be potent (doses < 2 mg); must be able to permeate skin sufficiently for systemic effects; must be nonsensitizing, nonirritating

Question 16

local inhalation route: advantages and disadvantages:

Answer 16

Adv: Application of aerosolized particles at site of action in lungs increases local topical effects and reduces systemic effect
Dis: Effects dependent on particle size: < 0.5 µM –> exhaled (no effect), 1-5 µM –> deposited in small airways (therapeutic effect), > 10 µM –> deposited in oropharynx (side effects); Irritant drug may induce bronchospasm

Question 17

local topical route: advantages and disadvantages:

Answer 17

Adv: Generally minimal systemic absorption, Greater potential for systemic availability in children due to greater ratio of body surface area to weight