Pharmacology

Question 1

Cell cycle phases

Answer 1

G0 - resting
G1 - cell enlarged and makes new protein
S - DNA replication
G2 - preparation for division
M - cell division (mitosis)
Cytostatic agents - G1 - cell remains viable
Checkpoint inhibitors at end of G1 - point at which cell commits to completing cell cycle
Cytotoxic agents - S-M phase - cell dies

Question 2

How do you calculate the relative bioavailability?

Answer 2

Relative bioavailability = (AUCA x DoseB) / (AUCB x DoseA)

Question 3

How do you calculate the therapeutic index of a drug?

Answer 3

• Therapeutic index (or ratio), is a comparison of the amount of a therapeutic agent that causes the therapeutic effect (for 50% of patients) to the amount that causes toxic effects (for 50% of patients)
• Therapeutic index = dose for toxic effect/therapeutic dose

Question 4

How do you calculate a corrected sodium in hyperglycaemia?

Answer 4

Sodium (corrected) = Sodium (measured) + (glucose / 4) (all values in mmol/L).

Question 5

P450 CYP3A4 inhibitors - action and examples

Answer 5

• Increase other medications (Inhibitors)
• Grapefruit, pomegranate
• Erythromycin, clarithromycin
• Doxycycline
• Metronidazole, fluconazole, ketoconazole
• HIV protease inhibitors
• Chloramphenicol
• CCBS - nifedipine, verapamil

Question 6

P450 CYP3A4 inducers - action and examples

Answer 6

• Decrease other medications (inDucers)
• St Johns Wort
• Rifampicin, isoniazid
• Carbamazepine, phenobarbitone, phenytoin

Question 7

Rituximab targets?

Answer 7

CD20

Question 8

Infliximab targets?

Answer 8

TNFa

Question 9

Anakinra targets?

Answer 9

IL-1

Question 10

Tocilizumab targets?

Answer 10

IL-6

Question 11

Tricyclic antidepressant overdose

Answer 11

• e.g. amitriptyline, nortriptyline, imipramine
• Blind as a bat (dilated pupils)
• Mad as a hatter (confusion, grabbing invisible objects)
• Red as a beet (flushed skin, tachycardia)
• Hot as hell (hyperthermia)
• Dry as a bone (dry mouth, urinary retention)
• ECG: wide QRS, QT elongation, arrhythmia
• Can develop seizure and coma
• Can develop ileus, prolonging toxicity
• > tx with sodium bicarbonate - maintain pH 7.5-7.55, may need I+V (hyperventilate)

Question 12

Flumazenil is an antidote for?

Answer 12

Benzodiazepine overdose

Question 13

Fomepizole is an antidote for?

Answer 13

Ethylene glycol (antifreeze) overdose, methanol overdose

Question 14

Sodium Ethylenediaminetetraacetic acid (EDTA) is an antidote for?

Answer 14

Heavy metals (eg. Lead, cyanide)

Question 15

Discuss the use of hydroxyurea in sickle cell disease

Answer 15

• MOA unknown, may be due to inhibition of ribonucleotide reductase
• It is the only medication proven to reduce painful episodes and also has been shown to improve quality of life and overall survival
• It is myelosuppressive and may lead to anaemia, neutropaenia and thrombocytopaenia

Question 16

Inhibitors of cytochrome P450

Answer 16

• Cause a build up of medication, leading to side effects

- e.g. grapefruit juice, fluconazole, fluoxetine, sodium valproate, ciprofloxacin, erythromycin

Question 17

Inducers of cytochrome P450

Answer 17

• Cause a decrease of medication, leading to decreased activity. Need larger doses to achieve desired effect
• e.g. carbamazepine, phenytoin, phenobarbitone

Question 18

Volume of distribution

Answer 18

Vd = total amount of drug in body / concentration of drug in plasma

Question 19

How does cytochrome P450 metabolise drugs?

Answer 19

Oxidation, hydrolysis, hydroxylation

Question 20

How do you calculate the clearance of a drug?

Answer 20

Cl = conc in urine x volume of urine / conc in plasma