A Pharmacist's Guide to Prescribing in Liver Impairment

In primary care clinical practice, pharmacists encounter two key considerations when dealing with liver impairment: (1) prescribing in hepatic impairment, and (2) monitoring requirements that may involve liver function tests (LFTs). It is crucial to differentiate between these two aspects in order to correctly interpret information from guidelines.

1. Prescribing in Hepatic Impairment: When the British National Formulary (BNF) advises caution or recommends avoiding certain drugs in cases of mild, moderate, or severe hepatic impairment, it's important to understand that this advice may not directly correspond to liver enzyme levels. Not all cases of liver impairment will show elevated enzyme levels. For instance, some patients with significant liver fibrosis may present with normal enzyme levels within the reference range.

Liver disease is generally classified into four stages:

• Stage 1 (Mild): Characterized by inflammation and temporary liver damage.

• Stage 2 (Moderate): Progression to fibrosis, where scar tissue formation occurs.

• Stage 3 (Severe): Unchecked fibrosis leads to cirrhosis, with more scar tissue than healthy tissue, significantly impairing liver function.

• Stage 4 (Liver Failure): Represents end-stage liver disease.

In determining the stage of a patient's liver disease, a complete clinical picture is required which can be obtained from a combination of consultations from the patient journal, correspondence from hepatology or gastroenterology, patient history, and blood test results.

Here is an example of advice in the hepatic impairment section for statins in the BNF:

2. Monitoring Requirements and LFTs: Individual drug monographs in the BNF provide essential information on potential hepatotoxicity. They specify the frequency of LFT monitoring and indicate when treatment should be stopped, often providing specific enzyme level thresholds, such as 3x the Upper Limit of Normal (ULN).

Here is an example of the Monitoring requirements section for statins in the BNF:

Another resource, "LIVER TOX", is also useful in this context, offering insights into drugs that can cause hepatotoxicity. BNF drug monographs and "LIVER TOX" provide clinical guidance in relation to pharmacodynamics- what the drug does to the body.

The BNF also gives guidance on how liver impairment affects the pharmacokinetics of the drug. What the body does to the drug in regards to: drug absorption, distribution, metabolism, and excretion (ADME).

Conclusion: Understanding the nuanced relationship between liver impairment stages, LFTs, and medication management is crucial for pharmacists in primary care. This knowledge ensures safe and effective medication use in patients with varying degrees of liver impairment.