From the Guidelines
It is not recommended to give a 50mg diphenhydramine capsule to a patient with liver cirrhosis due to the risk of decreased drug clearance and potentially toxic accumulation of the medication. Diphenhydramine is primarily metabolized by the liver, and patients with cirrhosis have impaired liver function, which can lead to increased levels of the drug in the system 1. For patients with liver cirrhosis, the dose of diphenhydramine should typically be reduced by 50-75%, meaning a 12.5mg to 25mg dose would be more appropriate.
The concern with normal dosing in these patients is that the drug may stay in the system longer, increasing the risk of side effects such as excessive sedation, confusion, urinary retention, and anticholinergic effects 1. These side effects could be particularly problematic in patients with advanced liver disease who may already have hepatic encephalopathy. In fact, the French recommendations for the diagnosis and management of hepatic encephalopathy suggest avoiding certain medications, including benzodiazepines, in patients with decompensated cirrhosis 1, and it is reasonable to exercise similar caution with diphenhydramine due to its potential to exacerbate hepatic encephalopathy.
Some key considerations for managing patients with liver cirrhosis include:
- Monitoring blood sodium levels in decompensated cirrhosis to prevent severe hyponatraemia, a predisposing factor for hepatic encephalopathy 1
- Limiting the prescription of proton pump inhibitors to their strict validated indications 1
- Avoiding the prescription of benzodiazepines in patients with decompensated cirrhosis 1
- Controlling precipitating factors for the development of hepatic encephalopathy, such as gastrointestinal bleeding, infection, dehydration, and constipation 1
If an antihistamine is needed for a patient with cirrhosis, it would be better to consult with their healthcare provider who might recommend an alternative medication with less hepatic metabolism or a reduced dose of diphenhydramine with careful monitoring.
From the Research
Diphenhydramine Administration in Liver Cirrhosis
- The administration of diphenhydramine in patients with liver cirrhosis requires careful consideration due to potential changes in drug disposition and pharmacokinetics 2.
- A study from 1984 found that diphenhydramine disposition was altered in patients with chronic liver disease, with a decreased plasma clearance and increased apparent volume of distribution, although these differences were not significant 2.
- The half-life of diphenhydramine was increased in patients with cirrhosis, which correlated with the severity of the disease 2.
Dosage Considerations
- There is limited information on the safe use of diphenhydramine in patients with liver cirrhosis, and dosing recommendations are often based on expert opinion 3.
- A review article from 2013 suggests that lower doses of medications are generally recommended in patients with cirrhosis due to altered pharmacokinetics, but data are limited on the correlation between pharmacodynamic effects and the degree of liver impairment 3.
- It is not explicitly stated in the available evidence whether a 50mg diphenhydramine capsule can be given to a patient with liver cirrhosis, but it is recommended to exercise caution and consider the potential for altered drug disposition and pharmacokinetics.
Alternative Considerations
- Other studies have investigated the use of alternative medications and treatments in patients with liver cirrhosis, such as propofol sedation for upper gastrointestinal endoscopy 4, and balloon-occluded retrograde transvenous obliteration for recurrent hepatic encephalopathy 5.
- A review article from 2018 discusses the pathophysiological mechanisms and treatment options for hepatic encephalopathy, a serious complication of liver cirrhosis 6.
- However, these studies do not provide direct guidance on the administration of diphenhydramine in patients with liver cirrhosis.