Metformin

Question 1

How much does Metformin lower A1C?

Answer 1

1-2%

Question 2

How does Metformin affect lipids?

Answer 2

Decreased TG and LDL by 8-15% and increases HDL by 2%

Question 3

How is Metformin eliminated?

Answer 3

90% renal, tubular secretion and glomerular filtration

Question 4

Primary target of Metformin?

Answer 4

Lowers hepatic gluconeogenesis and therefore lowers fasting blood glucose

Question 5

Which other drug lowers hepatic gluconeogensis?

Answer 5

Thiazolidinediones - but generally not used, due to ADRs

Question 6

Metformin’s secondary MOAs?

Answer 6

Increases insulin sensitivity in peripheral muscles

Reduces intestinal glucose absorption

Question 7

How does Metformin reduce intestinal glucose absorption?

Answer 7

By increasing anaerobic glucose metabolism

Question 8

Initial and Max dose for Metformin?

Answer 8

initial, 500mg BID

Max dose, 2,550mg

Max effective dose, 2,000mg/day

Usual dose: 1,000mg BID

Question 9

Metformin given with or without meals?

Answer 9

WITH meals, to reduce GI effects

Question 10

Metformin ADRs

Answer 10

Mostly GI - diarrhea, bloating, N/V, anorexia
metallic taste – 30% prevalence

Up to 30% patients develop B12 deficiency w macrocytic anemia&raquo_space;> The B12-intrinsic factor complex uptake by ileal cell membrane receptors is known to be calcium-dependent, and metformin affects calcium-dependent membrane action.

Question 11

Metformin Black Box Warning

Answer 11

Lactic Acidosis: RARE, metformin contraindicated w renal impairment or history of metabolic acidosis

Question 12

When might you need to hold Metformin dosing temporarily?

Answer 12

If patient undergoes radiographic dye studies - hold just prior to and a few days after

Question 13

Avoid use in these patients

Answer 13

Elderly, esp >80yrs

Renal impairment