The formalin test for nociception, which is predominantly used with rats and mice, involves moderate, continuous pain generated by injured tissue. In this way it differs from most traditional tests of nociception which rely upon brief stimuli of threshold intensity. In this article we describe the main features of the formalin test, including the characteristics of the stimulus and how changes in nociceptive behaviour may be measured and interpreted. The response to formalin shows an early and a late phase. The early phase seems to be caused predominantly by C-fibre activation due to the peripheral stimulus, while the late phase appears to be dependent on the combination of an inflammatory reaction in the peripheral tissue and functional changes in the dorsal horn of the spinal cord. These functional changes seem to be initiated by the C-fibre barrage during the early phase. In mice, the behavioural response in the late phase depends on the ambient temperature. We argue that the peripheral tissue temperature as well as other factors influencing the peripheral inflammation may affect the response, possibly confounding the results obtained with the test. Furthermore, we discuss the methods of recording the response and the value of observing more than one aspect of behaviour. Scoring of several behavioural variables provides a means of assessing motor or sensorimotor function as possible causes for changes in behaviour. In conclusion, the formalin test is a valuable addition to the battery of methods available to study nociception.

The effect of different formalin concentrations on the nociceptive response in the formalin test was examined in mice. Subcutaneous formalin injection induces 2 distinct periods of high licking activity: an early phase lasting the first 5 min, and a late phase lasting 20-30 min after the injection. Formalin concentrations of 0.02-0.2% induced only the early phase, while concentrations of 1% or more induced both the early phase and the late phase. The ability of the test to show the antinociceptive effect of morphine and acetylsalicylic acid was similar for high and low formalin concentrations. For both these analgesics, a lower dose was needed to induce antinociception in the late phase than in the early phase using the same formalin concentration. Indomethacin had no effect in the early phase. In the late phase indomethacin induced antinociception when 1% formalin was used, while no significant effect was observed using 5% formalin. Clear histological changes in the paw were demonstrated after formalin concentrations that induced both phases. Lower formalin concentrations induced only very small changes. Using a low formalin concentration (0.2%), repeated testing using the same paw could be performed at intervals of 1 week without any significant change in the response. It was concluded that the formalin concentration should be kept as low as possible to minimize the suffering of the animal. Formalin concentrations of 0.05-0.2% are recommended for studying the early phase. Formalin concentrations of 1% or higher have to be used when studying the nociceptive response in the late phase.

Background:Residents living in long-term care facilities are a vulnerable population. For many residents, a nursing home is their place of death. Palliative care and end-of-life decisions are important components of their care provision.Aim:To study the views of cognitively able residents and relatives on advance care planning, end-of-life care, and decision-making in nursing homes.Design:A qualitative study with in-depth interviews with nursing home residents and focus group interviews with relatives of nursing home residents. Analysis is based on interpretive description.Setting/participants:In total, 43 informants from nine nursing homes participated in the study (25 nursing home residents and 18 relatives). All included residents had capacity to provide informed consent and lived in long-term care.Results:The main findings of this study were the differing views about decision-making and advance care planning of residents and relatives. Residents do trust relatives and staff to make important decisions for them. The relatives are in contrast insecure about the residents’ wishes and experience decision-making as a burden. The majority of the residents had not participated in advance care planning. None of the residents stated challenges connected to end-of-life care or mentioned the wish for euthanasia.Conclusion:Although most residents seem to be satisfied with decision-making and end-of life care, there is a need for systematic advance care planning. Advance care planning could help to explore future wishes for care and ease decision-making for the relatives, physicians, and staff and should be offered to all cognitively able nursing homes residents.

MP 32 mg daily did not provide additional analgesia in patients with cancer receiving opioids, but it improved fatigue, appetite loss, and patient satisfaction. Clinical benefit beyond a short-term effect must be examined in a future study.