Module 2: Absorption Flashcards

Question

What is a drug that has enteric coating? | - Provide an example

Answer 1

Drugs with enteric coating are covered with a special coating that prevents their dissolution in the acidic environment of the stomach. - Ex. Drugs that cause damage to the stomach

Answer 2

Once the drug passes into the more alkaline duodenum

Answer 3

Bioavailability is the fraction of a dose of drug that reaches the systemic circulation unchanged.

Answer 4

1. Drug formulation 2. Route of Administration 3. Degree of Metabolism

Answer 5

Involves placing a drug under the tongue. - The drug dissolves and is absorbed across the oral mucosa - Venous drainage from the oral mucosa is to the superior vena cava, the superior vena cava takes blood to the heart - Drugs administered sublingually avoid first pass metabolism through the liver - Lipophilic and uncharged.

Answer 6

Typically patches, ointments, sprays or lotions which provide constant plasma drug levels with minimal peaks and troughs

Answer 7

The epidermis provides a lipid barrier... therefore, drugs must be lipophilic enough to penetrate the skin - Drugs must also be relatively hydrophilic in order to dissolve in the extracellular fluid

Answer 8

... lipophilicity and some degree of hydrophilicity and are usually small (< 600 Da) molecules

Answer 9

Tolerance may develop unless drug-free periods are enforced | - Typically, patches are removed for 6 – 10 hours per day to avoid tolerance.

Answer 10

1. Thickness of the skin – Transdermal absorption is inversely proportional to skin thickness. 2. Hydration – Transdermal absorption is increased when the skin is well hydrated. 3. Hair follicles – Provide routes for drugs to bypass the barrier function of the epidermis. - In general, the greater the number of hair follicles, the greater the transdermal absorption is. 4. Application Area – The greater the application area, the greater the transdermal absorption. 5. Integrity of the barrier – In conditions such as psoriasis, burned or abraded skin, transdermal absorption is increased.

Answer 11

Useful when the patient is unconscious or vomiting.

Answer 12

Approximately 50% of rectally administered drugs bypass the liver (an important site for drug metabolism).

Answer 13

Administration: The drug is inserted into the rectum as a suppository - The suppository dissolves and the drug cross the rectal mucosa into the blood.

Answer 14

Disadvantages include incomplete absorption and some drugs may irritate the rectal mucosa.

Answer 15

Drug is injected directly into a peripheral vein - Most commonly used veins are those on the back of the hand or the median cubital vein at the elbow although any visible vein may be used.

Answer 16

1) In IV bolus a single dose is administered over a short time period. 2) In an IV drip a drug is administered under continuous infusion over a prolonged period - Drugs are typically diluted in a “vehicle” such as saline in an IV bag

Answer 17

Advantages: - No barriers to absorption, bioavailability is 100%. - Allows precise control of drug dosage & duration of action. - Allows administration of poorly soluble drugs that must be diluted in a large volume. - Allows injection of drugs that are irritants (i.e. chemotherapeutic drugs) they can be injected slowly, diluted in blood Disadvantages: - Expensive, invasive and inconvenient. - Drug cannot be removed once injected. - Risk of infection and fluid overload. - Risk of injecting wrong formulation (IM formulation sometimes injected IV by accident).

Answer 18

Drug is injected beneath the skin into the subcutaneous tissue.

Answer 19

The only barrier to absorption is the capillary wall.

Answer 20

• Irritant drugs must not be injected subcutaneously as this will cause severe pain and/or tissue sloughing.

Answer 21

1) Blood flow | 2) Water solubility

Answer 22

Drug is injected directly into muscle tissue.

Answer 23

Absorption is determined by the ability of the drug to pass through fenestrations in the capillary wall - Blood flow

Answer 24

Advantages: - Can be used for poorly soluble drugs - Can use it to administer depot preparations (preparations in which the drug is absorbed slowly over time). Disadvantages: - Pain/discomfort - May cause local tissue and/or nerve damage if the injection is done improperly

Answer 25

Blood flow is different depending on which muscle is used for injection - In general blood flow is deltoid > vastus lateralis> gluteal - Exercise increases blood flow and may therefore increase absorption for IM drugs. - Blood flow may be decreased in heart failure, severe hypotension and hypothermia

Answer 26

Gaseous and volatile drugs can be inhaled and absorbed into the blood through the pulmonary epithelium. 1) Absorption is very rapid (almost instantaneous) due to the large surface area of the lung. 2) In the case of pulmonary disease (i.e. asthma), the drug is delivered to its site of action which is a major advantage. Drugs such as general anaesthetics used in surgery are also often administered by the pulmonary route of administration.