Patients with severe decompensated liver disease usually have associated renal impairment, with obvious consequences for drugs eliminated predominantly by the kidney. Where facilities exist, dosing should be guided by plasma concentration monitoring, e.g. of theophylline, lidocaine and phenytoin.
These changes in drug response (in particular) and in disposition affect prescribing, as is now discussed.
Prescribing for patients with liver disease
If liver disease is stable and well compensated, prescribing of most drugs is safe. Particular care should attend evidence of:
• Impaired hepatic synthetic function (hypoalbuminaemia, impaired blood coagulation)
• Current or recent hepatic encephalopathy
• Fluid retention and /or renal impairment
• high hepatic extraction
• high plasma protein binding
• low therapeutic ratio
• CNS depressant effect.
When a drug undergoes significant hepatic metabolism, a reasonable approach is to reduce the dose to 25-50% of normal and monitor the response carefully. The following are comments on specific examples:
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