Formalin test in mice, a useful technique for evaluating mild analgesics

J Neurosci Methods. 1985 Jun;14(1):69-76. doi: 10.1016/0165-0270(85)90116-5.


A modification of the formalin test appropriate for testing of mice is described. Formalin 1 or 5% was injected into the dorsal surface of a hindpaw, and the time the animal spent licking the paw was recorded. On the basis of the response pattern, two distinct periods of intensive licking activity were identified; an early (0-5 min after injection) and a late response (20-30 min after injection). The following analgesics were investigated (dose range): acetylsalicylic acid (100-400 mg/kg), paracetamol (100-400 mg/kg) and morphine (0.6-10 mg/kg). Acetylsalicylic acid (200-400 mg/kg early response, 300-400 mg/kg late response), paracetamol (200-400 mg/kg early response, 300-400 mg/kg late response) and morphine (2.5-10 mg/kg) inhibited the responses in a dose-dependent manner. The results indicate that the test is useful for evaluating mild analgesics. It may have advantages over some of the tests that are commonly used for testing analgesics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaminophen
  • Analgesics*
  • Animals
  • Aspirin
  • Behavior, Animal / drug effects*
  • Formaldehyde*
  • Hindlimb
  • Male
  • Mice
  • Mice, Inbred Strains
  • Morphine
  • Reaction Time / drug effects


  • Analgesics
  • Formaldehyde
  • Acetaminophen
  • Morphine
  • Aspirin