Opiates

Question 1

pKa 8
VD (L/kg) 3.5
Unionised fraction % 23
Relative potency 1
Relative lipid solubility 1
Protein binding % 30
Oral bioavailability 25

Answer 1

Morphine

Question 2

pKa 7.6
VD (L/kg) 5
Unionised fraction % 37
Relative potency 2
Relative lipid solubility 250
Protein binding % 40
Oral bioavailability low

Answer 2

Diamorphine

Question 3

pKa 8.2
VD (L/kg) 5.5
Unionised fraction % pro-drug
Relative potency 0.1
Relative lipid solubility pro-drug
Protein binding % 7
Oral bioavailability 50

Answer 3

Codeine

Question 4

pKa 8.7
VD (L/kg) 4
Unionised fraction % 5
Relative potency 0.1
Relative lipid solubility 30
Protein binding % 60
Oral bioavailability 50

Answer 4

Pethidine

Question 5

pKa 8.4
VD (L/kg) 4
Unionised fraction % 9
Relative potency 100
Relative lipid solubility 600
Protein binding % 83
Oral bioavailability 33

Answer 5

Fentanyl

Question 6

pKa 6.5
VD (L/kg) 0.8
Unionised fraction % 90
Relative potency 20
Relative lipid solubility 90
Protein binding % 90
Oral bioavailability N/A

Answer 6

Alfentanyl

Question 7

pKa 7.1
VD (L/kg) 0.4
Unionised fraction % 68
Relative potency 100
Relative lipid solubility 20
Protein binding % 70
Oral bioavailability N/A

Answer 7

Remifentanyl

Question 8

Half life

Answer 8

Time taken for plasma conc of a drug to reduce to half its original value

Question 9

Elimination

Answer 9

Amount of drug cleared from blood per unit time

Question 10

Clearance

Answer 10

Volume of blood cleared of drug per unit time

Question 11

Elimination half life

Answer 11

Time taken for conc of drug to decrease by half its starting dose in the body