Substance misuse - Prescribing for alcohol misusers

Measuring extent of liver damage and assessing likely drug interactions is key.

Ascites may need to be controlled with diuretics in endstage disease
Ascites may need to be controlled with diuretics in endstage disease

There are no definite scientifically proven limits to what constitutes safe alcohol consumption, but there are consensus guidelines on when drinking becomes dangerous to health.

The best way to assess the level of drinking is by using the AUDIT questionnaire (Alcohol Use Disorder Identification Test)1 or one of its derivates, such as AUDIT-PC, which is designed to be used in primary care. It is a better test to detect problematic alcohol use than any blood test2 and is regarded as the standard screening tool to identify harmful and dependent drinking.

Two organs are significantly affected when alcohol is consumed: the liver including intestines, and the brain including peripheral nerves.

Liver
The term cirrhosis is a histo-pathological term used when looking at a liver biopsy. Cirrhosis is the endstage of fibrosis, which is the replacement of normal liver tissue with collagen.

Alcohol is the most common cause of chronic liver disease in western civilisations, but other contributing factors may also be present. Conditions such as hepatitis C are treatable and can make a difference to prognosis.

There are other, less invasive and more practical tests than a liver biopsy. The most widely used is the LFT. This is a misleading term, as it does not actually measure the functioning of the liver, but the degree of liver cell damage.

The test measures blood levels of the enzymes AST, ALT, ALP and GGT, and looks at the amount of enzymes released by damaged cells.

Two other measurements commonly part of LFTs, bilirubin and albumin, are products or precursors of products of the liver. This is important to remember when assessing patients with suspected liver damage. In cases where there is very little liver remaining, LFTs might be normal.

A more sensitive and specific marker of liver function is to measure clotting time, as this is exclusive to the liver.

The INR level is a very good indicator of how well the liver is functioning.

Albumin, bilirubin and INR, together with the grade of ascites and encephalopathy, are part of the Child-Pugh score, which is the standard to assess liver failure.

In most cases, an ultrasound of the liver will reveal any structural abnormalities and this completes the assessment. Some specialists also measure the degree of fibrosis with a modified ultrasound scan.

Brain
Alcohol has direct toxic effects on brain and nerve cells.

The main concern is a lack of thiamine due to malnutrition, which can result in Wernicke's encephalopathy and, in the long term, may result in Wernicke-Korsakoff syndrome.

This represents irreversible brain damage.

Considering this, it is good practice to prescribe thiamine supplements to harmful, hazardous and dependent drinkers. As the absorption of thiamine tablets is not very good, some sources recommend giving thiamine as an IM injection. However, the formulation used for this can be quite painful when injected and patients often prefer the tablet form.

Prescribing considerations

  • Consider prescribing a PPI and thiamine supplement for hazardous or harmful drinkers.
  • Benzodiazepines or opioids can be dangerous. Some benzodiazepines are metabolised using the cytochrome P450 pathway, which might potentiate their sedating effect in a damaged liver.
  • There is reduced ability to metabolise drugs through the liver. There is no easy way to remember which drugs are affected. If in doubt, check the Summary of Product Characteristics.
  • Anti-inflammatories such as aspirin have a considerable risk of GI bleeds in patients who misuse alcohol.
  • Prescribe opioids over NSAIDs for analgesia, but be careful with the dosage and consider co-prescribing of laxatives if needed.
  • Drug interactions can be rare and unfamiliar to the prescriber. Regular clinical reviews are important when starting any new drug.
  • Anti-craving medication such as acamprosate is usually safe to prescribe even in advanced liver failure.

Palliative care
Palliative care is very important for patients with endstage liver failure, but who are not suitable for a liver transplant.

Apart from symptom control, which is not different to any other endstage disease, there are some specific considerations, especially preventing GI bleeding with PPIs and controlling ascites with diuretics.

  • Dr Grimm is a GPSI in substance misuse in West Yorkshire, and a clinical lead for the RCGP alcohol certificate

References
1. Saunders JB, Aasland OG, Babor TF et al. Development of the alcohol use disorders identification test (AUDIT): WHO collaborative project on early detection of persons with harmful alcohol consumption - II. Addiction 1993; 88: 791-803.

2. Coulton S, Drummond C, James D et al. Opportunistic screening for alcohol use disorders in primary care: comparative study. BMJ 2006; 332(7540): 511-17.

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