Renal: Introduction

Last updated: Friday, August 03, 2018

NB: See learning outcomes for this tutorial mapped to competencies, a PDF of the whole text, and a one-page summary.

☞ Why this subject matters...

Renal impairment is common in hospitals and pharmacists are often asked to help choose medicines that are safe in these patients, or to advise on dose reduction.

Prescribing in patients with renal failure is not an exact science. The practical knowledge of clinical professionals combined with some published evidence, and the basic principles of drug clearance provide the backbone of information available.

Drugs eliminated by the kidney

Most systemically administered drugs are eliminated at least partly by the kidney, even if it is only a tiny proportion of the dose. However, for some drugs, the kidney is the major site for elimination of unchanged drug and these are particularly liable to require careful dose adjustment in renal dysfunction to prevent accumulation. Examples of drugs principally eliminated unchanged by the kidney include:
In addition, there are drugs with therapeutic activity at least partly dependent upon metabolites that are excreted unchanged by the kidney. An example is allopurinol, which has an active metabolite called oxipurinol which works in the same way as the parent drug. Some drugs have toxic metabolites that are eliminated renally. For example nor-pethidine, a major metabolite of pethidine, can accumulate in renal failure to cause CNS toxicity such as convulsions.