Extremes Of Weight

Question 1

how do you calculate BMI and what do the numbers mean

Answer 1

weight(kg)/height^2 (m2)
less than 18- underweight
18-25-normal
25-30-overweight
30 above-obese

Question 2

what are the pK differences in obese and underweights patients?

Answer 2

TBW increased in BOTH- increased VD of hydrophilic drugs
Fat increased in OBESE, decreased in UNDERWEIGHT- increase VD of fat sol drugs in OBESE
LBW increased in OBESE, decreased in UNDERWEIGHT- increased drug clearance in OBESE
Plasma protein increased in OBESE, decreased in UNDERWEIGHT- increased binding in OBESE
Cardiac output increased in OBESE, decreased in UNDERWEIGHT- increased blood flow in OBESE so increased clearance

Question 3

explain paracetamol dosing in less than 40kg, 41-49kg and 50kg plus

Answer 3

less than 40- 500mg QDS (max 2g)
41-49- 1G TDS (max 3g)
50 plus- 1G QDS (max 4g)

Question 4

what blood thinners are ok in 120kg plus?

Answer 4

warfarin, apixaban or rivaroxaban- ideally warfarin cuz DOACs are lipophilic so go to fat tissue and decrease plasma concn so clot risk, increased enzymes so increased clearance and increased cardiac output also increases clearance

Question 5

what is the issue of DOACs in less than 50kg?

Answer 5

renal function- may be overestimated- less muscle so less creatinine so looks good

Question 6

what emergency contraception isnt effected by weght

Answer 6

CU-IUD

Question 7

who can have levo 1.5mg EC?

Answer 7

anyone less than 70kg

Question 8

who can have UA EC?

Answer 8

anyone under 85kg

Question 9

who should get levo 3mg ec?

Answer 9

anyone above 70kg if breastfeeding or on enzyme inducers like carbemazepine or st johns wart