Prescribing in Renal failure

This article describes about the various remedies which can be prescribed in Renal Failure.

Most of the drugs are eliminated through kidney and in case of renal failure they may accumulate causing toxicity. this article will discuss the drugs to be prescribed or not or if prescribed then how and when.
Even when principles of drug dosing in renal failure are followed, a substantial risk of drug related adverse events remain. If there is some residual renal function, drug may aggravate established renal impairment or aggravate the metabolic problems of renal failure or cause toxicity due to accumulation of drugs.

Drugs prescription avoided in renal impairment

The five commonest classes of drugs that aggravate renal impairment are aminoglycosides, ACE inhibitors, ARB, NSAIDs and radiological contrast media. Others are Vancomycin, Amphotericin B, Cisplatin and cyclosporine.

Nephrotoxicity due to Aminoglycoside is usually reversible but ototoxicity may cause irreversible vestibular damage. Concominant use of loop diuretics greatly increases the risk of ototoxicity. Renal impairment due to ACE inhibitors is usually but not always irreversible on withdraw of the drugs. Among radiological contrast, non-ionic contrasts are safer but do not eliminatethe risk. Fluid depletion aggravates the risk. Concominant use of metformin enhances renal toxicity and should be withdrawn 48 hours before the use of contrast.

Drugs whicch causes hyperkalemia should be avoided for example Potassium sparing diuretics, ACE inhibitors tablets, ARB and NSAIDS tablets. Tetracycline causes release of intracellular potassium. Second generation tetracyclines like doxycycline and minocyclines are safer.

Corticosteroids cause moderate rise in urea. Acetazolamide and metformin are contraindicated in renal failure as they cause metabolic acidosis. Aspirin in low dose is safe but needs to be stopped before surgery to prevent coagulopathy. Some drugs accumulate in renal failure and cause toxicity. Their dosing intervals are increased to decrease toxicity for example nitrofurantoin(peripheral neuropathy), acyclovir(confusional state),morphine(coma), digoxin(cardiotoxicity), fibrates(myopathy) and allopurinol(rash).

The loading dose of drugs do not vary much from the initial dose given to patients with normal renal functions except digoxin for which 50-70% of loading dose is reduced by for anticonvulsants and antiarrythmics.

Drug prescription safe in renal impairment

Certain drugs require no renal adjustment for example

Cefoparazone, Ceftriaxone, Moxifloxacin, Azithromycin, erythromycin,clarithromycin, clindamycin, metronidazole and piperacillin. Rifampicin used in tuberculosis is safe. Oral penicillins and cephalosporins except cephalexin and cefuroxime should be given in half the dose and intravenous Cephalosporins given once a day. Dose of piperacillin and tazobactum should be reduced. Imipenams and meropenams dosing interval is doubled.

Antifungals and antivirals
Ketoconazoles and miconazoles are safe. Voriconazole should be avoided, fluconazole and itraconazole dose should be halved. Griseofulvin is avoided.
Among antivirals lamivudine, stavudine require double dosing interval. Other anti retroviral require no change.

Oral hypoglycemics
Among the oral hypoglycemics pioglitazone and repaglinide are safe. Metformin should be avoided. Glimiperide and glipizide should be used in half the dose. Acarbose should be avoided when glomerular filteration rate in less than 10ml/min.

Among other important drugs PPI(proton pump inhibitors) like omeprazole, pantoprazole require no adjustment. Famotidine is given in one fourth of the dose. Antiplatelets and anticoagulants requires no adjustment except enoxaparin dose to be halved. Antilipidemic agents are safe. In beta blockers atenolol and sotalol require half thee dose. In ARB no adjustment is required except for Candesertan. All ACE inhibitors requirese 50% of the dose.

Though the list is unending and most commonly used drugs hin common diseases has been discussed.I suffice to say that prescribing for renal patients should be systematic and careful due to incidence of drug reaction in this group.



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