Routes of Administration: Pharmacokinetics

Question 1

Pharmacokinetics

Answer 1

The motion of medicines

Question 2

Absorbtion of drug

Answer 2

Movement of a drug from the site of administration to the bloodstream

Question 3

Distribution

Answer 3

Movement of drug around different tissues in the body

Question 4

Metabolism

Answer 4

Change of drugs into compounds which are easier to eliminate

Question 5

Excreation

Answer 5

Irreversible loss of (unchanged) drug from the body

Question 6

ADME

Answer 6

• Drug at site of administerationis absorbed
• Can be bound or unbound to dissolved protiens
• Drug at action site bound to receptor or distribution to diffrent tissues
• Unchanged drug excreated or metabolite excreation

Question 7

Drug plasma concentration

Answer 7

• Exeed Concentation - becomes toxic and side effects can occour
• Below the concentration - becomes not effective
• Onset point - when the drug is absorbed and becomes effective

Question 8

Bioavailability

Answer 8

• IV administeration means entire dose reaches systematic circulation 100% bioavailability
• Dependant on permeability drug route such as capsule or tablet

Question 9

First pass metabolism

(presystemic)

Answer 9

• Drug absorbed go straight through liver as it passess into the the portal heptic system
• Factor that contributes to bioavailability
• e.g. Used to combat opiate overdose rapid onset required

Question 10

Metabolism

Answer 10

• Predominately takes takes place in the liver but can also happen elsewhere
• Can be inhibited by other drugs

Question 11

Phase I metabolism

Answer 11

Oxidation, reduction, hydrolysis
Products are likely to be inactive and more water-soluble

Answer 12

addition of groups to the drug to increase its solubility
Conjugates include glucuronates and sulphates

Question 13

Oral adminstration

Answer 13

• Dosage form travels to the main sites of absorption – stomach and small intestines
• Drug must cross lipophilic barriers to be absorbed
• Amount of drug which enters the systemic circulation depends upon the bioavailability

Question 14

Advantages of parental route

Answer 14

• Useful if drug labile in GI tract
• Fast-acting
• Prolonged effect possible with IM
• Localised effect, e.g. intra-articular
• Drugs can be administered to unconscious patients
• 100% bioavailability for IV

Question 15

Inhalation route

Answer 15

• Drug is delivered directly to the lungs typically via an inhaler or a nebuliser
• Typically used for a local effect

Question 16

Advantages of Inhalation

Answer 16

• Smaller doses can be used
• Reduces the chance of unwanted systemic (side) effects
• Fast onset because drug delivered to the site of action
• Avoids first pass metabolism
• Variety of different dosage forms available

Question 17

Transdermal route

Answer 17

Involves the application of a drug to the skin surface with the intention of achieving a systemic effect

Question 18

Advantages of Transdermal

Answer 18

• Avoids first pass metabolism
• Controlled rate of drug delivery
• Reduces dosage frequency which can increase compliance

Question 19

Rectal route

Answer 19

• Typically used for the local delivery of drugs to the rectum, e.g. haemorrhoids
• Drug usually incorporated into a suppository which dissolves or melts within the rectum
• Foam formulations which expand to fill the rectum are also available
• Issues with pharmacokinetics and cultural acceptability