Pharmacology: Pharmokinetics, pharmacodynamics and teratogenic

Question 1

What is pharmokinetics

Answer 1

What body does to drug:

• Absorption
• Distribution
• Elimination

Question 2

Do lipid + water soluble drugs cross membranes easily?

Answer 2

Lipids - yes

water - no, need facilitated diffusion/active transport

Question 3

What is bioavailability?

Answer 3

Amount of drug that reaches circulation

Question 4

What is volume distribution?

Answer 4

volume of water in which the drug would be uniformly distributed

Question 5

What are the 2 phases of hepatic elimination?

Answer 5

Phase 1 reduction/oxidation/hydrolysis by cytochrome p450 to become inactive/active/toxic
Phase 2 conjunction with molecule to make more solable (glucuronate - basic drugs, acetate acidic drugs, sulphate - e.g. COCP)

Question 6

Which drugs that are eliminated from the liver are then excreted by bile → faeces?

Answer 6

molecular weight >300Da

Question 7

What does renal elimination depends on?

Answer 7

GFR

renal function

Question 8

What physiological changes in pregnancy effect pharmacokinetics?

Answer 8

Increased blood volume 
Increased renal blood flow & GFR
Increased 3rd space (AF + oedema)
Increased fat content 
Reduced albumin 
progressive insulin resistance

Question 9

Which drugs are commonly effected by increased clearance?

Answer 9

Anticonvulsants
Mood stabilisers (lithium)
Thyroxine

Question 10

Why does warfarin have reduced levels in pregnancy

Answer 10

Decreased plasma albumin (warfarin is protein bound)

Question 11

Why does chloroquine have reduced levels in pregnancy

Answer 11

Fat soluble, increased fat reservoir

Question 12

What is pharmacodynamics?

Answer 12

What the drugs does to the body

Question 13

What are the 4 major ways a drugs can effect the body?

Answer 13

Receptors
Enzyme interaction
Membrane ion channels
Metabolic processes

Question 14

What is the effect of phenytoin in COCP & why?

Answer 14

Reduced efficacy of COCP
Phenytoin potent inducer of C P450

Other inducers: Rifampicin, spironolactone

Question 15

How does ampicillin effect the efficacy of the COCP?

Answer 15

Ampicillin alters the gut flora and leads to reduced enters-hepatic recirculation

Question 16

Why should you avoid adding additional drugs to an epileptic woman on anti epileptics

Answer 16

Increased risk of teratogenesis

Question 17

Which drugs do not cross the placenta?

Answer 17

Heparin LMWH
Tubocurarine
Insulin

Question 18

Tetraogenesis is split into 3 main time periods, what are theses and how does the drugs effect on the fetus change during these periods?

Answer 18

Pre-embryonic <17day - Death/reabsortion/survival
Embryonic day 18-55 (week 2-8) - highest risk for teratogenesis
Post-embryonic 8 weeks to term: IUGR/specific organ function

Question 19

What % of women with epilepsy have a normal pregnancy

Answer 19

90%

Question 20

Which anti-epileptic had the highest risk? What side effect is seen in the fetus

Answer 20

Sodium valproate

Neural tube defect

Question 21

Which anti epileptic is considered safest?

Answer 21

Lamotrigine

Question 22

What congital malformation is seen with phenytoin + carbamaezipine

Answer 22

Cleft palate
microcephalt
cardiac abnormalities
mental retardation

Carb + neural tube defects

Question 23

How to minimise risk if patient on anti epileptics?

Answer 23

Pre conception folic acid
avoid poly pharmacy
lowest level to control seizures
Vit K to mothers from 36/40 and to baby

Question 24

Tetracycline effect

Answer 24

permanent teeth discolouration and impaired bone growth

Question 25

trimethoprim effect

Answer 25

effects folate metabolism

Question 26

nitrofurantoin

Answer 26

neonatal haemolysis

Question 27

When is warfarin contraindicated in pregnancy

Answer 27

6-12 weeks, 5% teratogenic
Only use after 12 weeks if very necessary
No relationship between maternal and fetal INR risk fetal intracranial haemorrhage

Question 28

What drugs are contraindicated in breastfeeding mothers

Answer 28

Cytotoxics 
Mood stabiliser lithium
Sedative bezos/barbituates 
Amiodarone 
Abx tetracycline metronidazole chloamphenicol 
COCP
Theophylline 
Aspirin (Reyes syndrome_