Pharmacology: Pharmokinetics, pharmacodynamics and teratogenic Flashcards
(28 cards)
What is pharmokinetics
What body does to drug:
- Absorption
- Distribution
- Elimination
Do lipid + water soluble drugs cross membranes easily?
Lipids - yes
water - no, need facilitated diffusion/active transport
What is bioavailability?
Amount of drug that reaches circulation
What is volume distribution?
volume of water in which the drug would be uniformly distributed
What are the 2 phases of hepatic elimination?
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)
Which drugs that are eliminated from the liver are then excreted by bile → faeces?
molecular weight >300Da
What does renal elimination depends on?
GFR
renal function
What physiological changes in pregnancy effect pharmacokinetics?
Increased blood volume Increased renal blood flow & GFR Increased 3rd space (AF + oedema) Increased fat content Reduced albumin progressive insulin resistance
Which drugs are commonly effected by increased clearance?
Anticonvulsants
Mood stabilisers (lithium)
Thyroxine
Why does warfarin have reduced levels in pregnancy
Decreased plasma albumin (warfarin is protein bound)
Why does chloroquine have reduced levels in pregnancy
Fat soluble, increased fat reservoir
What is pharmacodynamics?
What the drugs does to the body
What are the 4 major ways a drugs can effect the body?
Receptors
Enzyme interaction
Membrane ion channels
Metabolic processes
What is the effect of phenytoin in COCP & why?
Reduced efficacy of COCP
Phenytoin potent inducer of C P450
Other inducers: Rifampicin, spironolactone
How does ampicillin effect the efficacy of the COCP?
Ampicillin alters the gut flora and leads to reduced enters-hepatic recirculation
Why should you avoid adding additional drugs to an epileptic woman on anti epileptics
Increased risk of teratogenesis
Which drugs do not cross the placenta?
Heparin LMWH
Tubocurarine
Insulin
Tetraogenesis is split into 3 main time periods, what are theses and how does the drugs effect on the fetus change during these periods?
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
What % of women with epilepsy have a normal pregnancy
90%
Which anti-epileptic had the highest risk? What side effect is seen in the fetus
Sodium valproate
Neural tube defect
Which anti epileptic is considered safest?
Lamotrigine
What congital malformation is seen with phenytoin + carbamaezipine
Cleft palate
microcephalt
cardiac abnormalities
mental retardation
Carb + neural tube defects
How to minimise risk if patient on anti epileptics?
Pre conception folic acid
avoid poly pharmacy
lowest level to control seizures
Vit K to mothers from 36/40 and to baby
Tetracycline effect
permanent teeth discolouration and impaired bone growth
