Pharmacology - Diabetes Mellitus Flashcards
(69 cards)
What is the mechanism of action of metformin?
→ Reduces gluconeogenesis in the liver by activating AMP-activated protein kinase
→ May also enhance tissue sensitivity to insulin – ↑tissue glucose uptake
What is the bioavailability of metformin?
40-60% by PO
What is the duration of action of metformin?
8-12h
How long does it take for the onset of clinical effect of metformin?
Days
Max effects take up to 2 week
How much plasma protein binding does metformin exhibit?
minimal
What is the half-life of metformin?
3h
How is metformin eliminated?
90% excreted unchanged in urine
Does metformin require dose adjustments?
Yes, for renal impairment
What is the initiation dose for metformin IR?
500-850mg oD
What is the max dose for metformin IR?
2500-2550mg daily
How should metformin IR be titrated upwards?
Can titrate upwards in 500-850mg intervals Q1-2 weeks divided OD-TDS
What is the initiation dose for metformin XR?
500mg OD
How should metformin XR be titrated upwards?
Can titrate upwards in 500mg intervals weekly
What is the max dose for metformin XR?
2000mg divided into OD or BDX
If >2000mg needed, switch to IR
What are the adverse effects of metformin?
→ Anorexia – bec it ↓appetite, but may reduce it TOO MUCH
→ GI disturbances – diarrhoea (weight loss), vomiting, indigestion
→ Metallic taste
→ ↑ risk of vit B12 malabsorption – B12 deficiency in long-term
→ Use w caution in patients w renal impairment – cannot excrete fast enough, accumulates in kidneys
→ Use in caution in patients at risk of lactic acidosis – esp in patients w hepatic, cardiovascular issues
What are the contraindications for metformin?
→ GFR < 30ml/min
→ Hypoxic states or at risk for hypoxemia – ↑ risk for lactic acidosis
eg Sepsis, respiratory failure, liver impairment, alcoholism, ≥80yo, HF, acute decompensated HF
What DDIs are there with metformin?
→ Alcohol – increases risk for lactic acidosis
→ Iodinated contrast material – stop for ≥48h after admin, restart when renal function is stable
→ Inhibitors/Inducers of OCT
When should metformin be taken?
Can be taken regardless of meals
If GI Sx, take with or immediately after meal
What is the mechanism of action of pioglitazone?
→ PPARgamma agonist – promotes glucose uptake into skeletal muscle and adipose tissue
→ Does not affect insulin secretion but increases insulin sensitivity
How long does it take for the effects of pioglitazone to show up?
1 month for max effect
How is pioglitazone eliminated?
liver
Can pioglitazone be used in liver impairment?
Yes, but use w caution (monitor LFTs)
What are the adverse reactions associated with pioglitazone?
→ Hepatoxicity – monitor liver function test before initiating and periodically thereafter
→ Fluid retention – monitor for HF after initiation/dose adj (Use w caution in NYHA Class I or II)
→ ↑ Fracture risk (more in women)
→ Dose-related weight gain
→ Risk of bladder cancer
→ Increased risk of hypoglycemia if also on insulin
What are the contraindications for pioglitazone?
→ Active liver disease
→ Symptomatic or Hx of HF (esp NYHA Class III-IV)
→ Active or Hx of bladder cancer