DM Pharmacology Flashcards
Biguanides
indication
Indication: Monotherapy with diet and exercise OR in combination with other agents/insulin for T2DM
- Off label: polycystic ovarian syndrome (PCOS).
Biguanides
moa
MOA:
Primary: decrease hepatic glucose production (inhibits gluconeogenesis in liver = increase AMP-activated protein kinase)
Secondary: increase peripheral/muscle glucose uptake and utilization (increase insulin sensitivity)
Biguanides
(Dosages and administration)
Metformin IR
250mg 500mg 850mg 1000mg
Start with 500-850mg OD
Increase by 500-850mg OD every 1-2 weeks in divided doses.
Max dose 2500 – 2550 mg OD.
Metformin XR
500mg 750mg 1000mg
Start with 500mg OD
Increase by 500mg weekly.
Max dose 2000mg OD. May divide dose to 1000mg BD if glycaemic control not achieved with OD dosing.
If dose >2000mg needed, switch to IR
Biguanides
PD PK
PD
Onset within days max 2 weeks
PK
A: Oral, F 40-60%, DOA: 8-12h
D: Rapidly distributed, minimal plasma protein binding. T1/2 3h
M: NA
E: Renal elimination, 90% in urine unchanged.
Biguanides
ADR
Common:
GI disturbances (diarrhoea, N/V, indigestion), anorexia, loss of appetite, metallic taste.
Usually transient and to take with food and increase dose regularly to minimise GI disturbance.
Long term:
May decrease serum B12.
Consider periodic measurement esp in those with anemia, peripheral neuropathy, or symptoms such as numbness, tingling.
Rare but fatal:
Lactic acidosis (3/100,000 patients/year)
Symptoms – N/V, abdominal pain, shallow/labored breathing, mental confusion.
Biguanides
DDI
DDI
EtOH/alcohol:
Increase risk of lactic acidosis.
Iodinated contrast material (for radiologic procedures e.g., x-rays, CT scan):
Temporarily withhold metformin for ≥48 hours after administration. Restart when renal function is stable and acceptable post procedure.
(Metformin may accumulate)
Organic cationic transporters (OCT) inhibitors/inducers e.g., cimetidine, dolutegravir, ranolazine):
May increase metformin by decreasing its renal elimination.
Biguanides
Contra
Contraindications
Severe renal impairment (GFR <30ml/min)
Hypoxic states/hypoxia risk (increased risk of lactic acidosis)
E.g.,
HF (avoid use in acute decompensated heart failure), sepsis, respiratory failure, liver impairment, alcoholism, ≥80 yo
Biguanides
Special population
May be considered for pregnancy patients with T2DM (low risk)
Require renal dose adjustment.
Metformin IR suitable for children ≥10 years; metformin XR not suitable for children.
Biguanides
Comments
Decreases A1c by 1.5%.
Negligible weight gain and hypoglycaemia.
- Good for obese patients (loss of appetite) and elderly patients (low risk of hypoglycaemia)
Possible reduction in CV with T2DM.
Prevent and delay T2DM.
OK for pregnancy.
thiazolidinediones
(Drug Dosage Administration
Pioglitazone 15mg , 30mg (tablet)
Start with 15mg or 30mg OD
Increase dose by 15mg
Max 45mg OD
thiazolidinediones
MOA
Peroxisome proliferator activated receptor gamma ( PPARgamma ) agonist to promote
glucose uptake into target cells (skeletal muscle/adipose tissue)
- ↓insulin resistance; ↑ increase insulin sensitivity
- No effects on insulin secretion
thiazolidinediones
PD PK
PD
Up to one month for max effect
PK
Liver elimination
thiazolidinediones
(ADR)
Hepatotoxicity
Monitor LFT prior to initiation and periodically thereafter.
Do not initiate therapy/discontinue if ALT > 3xUNL.
If ALT > 1.5xULN during therapy, repeat LFT weekly until normal.
Discontinue if s/sx of hepatic dysfunction regardless of ALT level.
Fluid retention
Caution use in NYHA Class I and II HF
Monitor s/sx of HF after initiation/dose adjustment.
Monitor weight gain from fluid retention.
Fracture (increased risk, esp women)
Risk of bladder cancer
Increased risk of hypoglycaemia with insulin therapy.
thiazolidinediones
(Contraindications
Contraindications
Active liver disease
Symptomatic or history of HF (esp class III to IV)
Active/history of bladder cancer.
thiazolidinediones
DDI
DDI
CYP3A4 AND CYP2C8 inhibitors and inducers
thiazolidinediones
(comments)
Decreases A1c by 0.4 - 1.4%.
**has some weight gain effects
**
Appears beneficial to patients with fatty liver disease (NAFLD and NASH)
CV effects
Potential reduction in risk of stroke
Increase risk of HF
Progression of diabetes kidney disease (neutral)
sulfonylureas
MOA
Primary: stimulate insulin secretion by blocking K+ channel of b-cells in pancreas islets (NEED BETA CELLS TO WORK).
- Targets the b-cell ATP-sensitive potassium (K ATP) channel, which controls the b-cell membrane potential.
- Binds to the SU receptor protein subunits of the K ATP channel inhibits K ATP channel mediated K+ efflux depolarisation opens voltage gated Ca channel trigger calcium dependent exocytosis of insulin granules from b-cells.
Secondary: decrease hepatic glucose output and increase insulin sensitivity.
glipizide (Drug Dosage Administration PD PK )
Glipizide
5mg 10mg (tablet)
5 mg BD (max dose 40mg/day)
Onset 12-24 hours
Inactive metabolite
A: F>95%
Onset: 1/2h
DOA: 12-24h
D: Binds extensively (99%) to plasma proteins (primarily albumin)
T1/2 4h
M: Hepatic 90%, hydroxylation
E: <10% excreted unchanged in urine + faeces. metabolites are excreted in urine + faeces.
sulfonylureas
DDI
DDI
Betablockers
May mask the signs and symptoms of hypoglycaemia.
EtOH/alcohol
Disulfiram-like reactions
(1st gen»> 2nd/3rd gen)
Flushing, tremors. Usually, 1-2 glasses a day is okay, however if patient drinks a lot, to avoid dosing.
CYP2C9 inhibitors e.g., amiodarone, 5FU, fluoxetine)
sulfonylureas
ADR
Hypoglycaemia
Use with caution in patients with irregular meal schedules.
Use with caution in elderly patients as more likely to have kidney failure titrate dose.
Weight gain (appx 2-5kg)
Exercise to minimise weight gain.
Sulfonylurea
Contraindications
Contraindications
Hypersx due to SUs