Prescribing for patients with kidney disease and electrolyte disorders Flashcards
What are the five grades of CKD based on eGFR?
Stage 1 - evidence of kidney damage with normal or increased GFR >=90
Stage 2 - evidence of kidney damage with mild reduction in GFR 60-89
Stage 3 - moderate reduction in GFR 30-59
Stage 4 - severe reduction in GFR 15-29
Stage 5 - Kidney failure <15 or on dialysis
How do NSAIDs cause a worsening of renal function?
One of the main actions of these drugs is the inhibition of COX enzymes and prostaglandin synthesis. This results in altered renal blood flow and reduced GFR. Patients with renal artery stenosis, cardiac failure and liver cirrhosis are more vulnerable to NSAID-induced changes in glomerular filtration pressure. Also more likely if used in combination with diuretics and/or ACEi.
They may also cause acute interstitial nephritis.
How do NSAIDs worsen hypertension and cardiac failure?
Salt and water retention
Which diuretics should be given to patients with renal failure?
Thiazides can be used in patients with GFR above 3, but are less effective below this. Loop diuretics can be given to patients with GFR<30, but beware of inducing AKI by over-diuresis.
What is the risk of giving spironolactone to a patient with CKD?
Hyperkalaemia
Can you give beta blockers in CKD?
Carvedilol, metoprolol and propanolol are metabolised by the liver and can be used at normal doses. Atenolol is renally excreted and bisoprolol is partially renally excreted, and may need reduction in the dose or frequency titrated to the patient’s BP and pulse.
Which drugs are first line for antihypertensives in patients with nephropathy?
ACEi and ARB, especially for those with proteinuria. The initial dose may need to be lower than usual, and a small number of patients e.g. those with bilateral renal artery stenosis, may develop nephrotoxicity. Baseline serum creatinine should be checked prior to starting and a rise in creatinine of above 30-50%, a fall in eGFR over 15% or hyperkalaemia should prompt investigation and possibly stopping treatment.
Why is nitrofurantoin ineffective in patients with a creatinine clearance <60?
It is concentrated in the urine.
How should the dose of digoxin be altered in CKD and what precautions should be taken?
A reduction in both initial and maintenance doses of digoxin may be required in patients with CKD because of reduced excretion and volume of distribution.
Serum digoxin levels should be checked regularly and it is important to avoid hypokalaemia.
Why does NICE recommend that metformin should not be used if eGFR <30?
Increased chance of lactic acidosis.
