Drug Choice & Special Case Prescribing

Question 1

What are the six steps of WHO good prescribing?

Answer 1

Define pts. problem
Specify therapeutic objective
Verify suitability
Start treatment
Give information
Monitor/stop treatment

Question 2

What is the Cockroft-Gault equation?

Answer 2

Calculates creatinine clearance (renal function)
CL(creatinine) = 1.23(m)/1.04(f) * (140-age) * Weight/
serum creatinine

Question 3

What is the eGFR?

Answer 3

Estimated Glomerular Filtration Rate (mL/min/1.73m2)

Question 4

What does the eGFR value reflect?

Answer 4

Renal function
>90 - Normal function
89-60 - Mild impairment
30-59 - Moderate impairment
15-29 - Severe impairment
<15 - Established renal failure

Question 5

How should prescribing change in renal impairment?

Answer 5

Use short acting agents (gliclazide)
Increase dosage interval (gentamicin)
Non-renally excreted alternatives (amlodipine)
Avoid some drugs (metformin)
Be aware of renal-requring drugs (thiazides)

Question 6

What are the four main pharmacokinetic changes in pregnant women?

Answer 6

Increased volume of distribution
Decreased plasma concentration
Increased renal excretion
Increased hepatic meabolism

Question 7

What drugs cross the placenta?

Answer 7

EVERY DRUG
Not Heparin (large mw, polar)

Question 8

What drugs cause the main problems in pregnancy prescribing? - The AuNTIes

Answer 8

Antiepileptics
Anticoagulants
Antibiotics
Antihypertensives
Antidiabetics
Antidepressants

Question 9

At what date are most pregnancies detected?

Answer 9

8-10 weeks

Question 10

What effects does Phenytoin (antiepileptic) cause in pregnancy?

Answer 10

Craniofacial abnormalities
Hypoplasia of distal phalanges
Growth deficiency
Mental deficiency

Question 11

What effect does Valproate (antiepileptic) cause in pregnancy?

Answer 11

Neural tube defects

Question 12

What effects does Carbamazepine (antiepileptic) cause in pregnancy?

Answer 12

Similar to Phenytoin

Lower risk

Question 13

How should treatment with antiepileptics be modified during pregnancy?

Answer 13

Continuation of treatment preferable
Can be planned discontinuation
Carbamazepine w/ 5g folic acid
Lamotrigine in tonic/clonic

Question 14

What effect does pregnancy have on the clotting system?

Answer 14

Produces a thombophilic state

Prevents post partum haemmorhage

Question 15

What effect does Warfarin have in pregnancy?

Answer 15

Teratogenic
-Chondroplasia punctata
-Optic atrophy
-Mental retardation
Avoid in T1/3 (LMWHs)

Question 16

What drugs commonly interact with oral contraceptives?

Answer 16

Antiepileptics (phenytoin/carbamazepine/phenobarbital are inducers)
Broad spectrum antibiotics
Rifampicin (inducer)

Question 17

What effects does hepatic impairment cause that affect prescribing?

Answer 17

Reduced clearance
Protein binding
Sodium retention
Coagulation
Gastric effects
CNS effects
Sedation