Published: 1 March 2018

Aspirin in Chloroform — More Harm than Help?

Prescriber Update 39(1): 2-3
March 2018

Key Messages

  • The Centre for Adverse Reactions Monitoring (CARM) has received a report of hepatotoxicity suspected to be linked to the topical use of aspirin in chloroform.
  • Chloroform is a possible human carcinogen and has been associated with hepatotoxicity.
  • Patients and pharmacy staff are exposed to chloroform when applying or compounding aspirin in chloroform.
  • The benefit-risk balance of topical aspirin in chloroform is unfavourable and the use of this mixture should be avoided.

The Centre for Adverse Reactions Monitoring (CARM) has received a report of the death of a 72-year-old female, who developed hepatotoxicity suspected by the treating physicians to be linked to topical application of aspirin in chloroform.

Aspirin in chloroform is compounded by pharmacists and pharmacy technicians and is used in the treatment of post herpetic neuralgia. It is an unapproved medicine in New Zealand but is currently funded by PHARMAC1.

A study conducted in 1993 found that chloroform did not improve the efficacy of the topical aspirin preparation, but improved its solubility2. There is no convicing evidence in scientific literature that aspirin dissolved in chloroform is effective for post-herpetic neuralgia.

Chloroform is classified by the International Agency for Research on Cancer as a group 2B carcinogen, being possibly carcinogenic to humans3. It is readily absorbed into the body after inhalation and oral or dermal exposure4.

Significant exposure to chloroform has been associated with hepatotoxicity in humans3,5. This is a potential risk for patients who are applying aspirin in chloroform multiple times per day for extended periods of time.

Acute exposure to chloroform can cause headaches, vertigo and dizziness5. Pharmacy staff and patients may experience these symptoms when compounding or applying aspirin in chloroform.

CARM has also received one report of a patient experiencing chemical burns after applying topical aspirin in chloroform.

Given the lack of evidence for efficacy and significant risk of harm, the benefit-risk balance for topical aspirin in chloroform is unfavourable and prescribers should use alternative medicines for their patients.

  1. PHARMAC. 2018. New Zealand Pharmaceutical Schedule 25(0). URL: (accessed 31 January 2018).
  2. King, R.B. 1993. Topical aspirin in chloroform and the relief of pain due to herpes zoster and postherpetic neuralgia. Archives of Neurology 50: 1046–53.
  3. World Health Organization. 1999. International Agency for Research on Cancer Monographs on the Evaluation of Carciongenic Risks to Humans: Some Chemicals that Cause Tumours of the Kidney or Urinary Bladder in Rodents and Some Other Substances 73: 131–82. URL: (accessed 31 January 2018).
  4. World Health Organization. 2004. Concise International Chemical Assessment Document 58: Chloroform. URL: (accessed 31 January 2018).
  5. U.S. Department of Health and Human Services. 1997. Toxicological Profile for Chloroform September 1997. URL: (accessed 31 January 2018).