Treating the pain of land-based envenomations is an acute care priority, since the discomfort may be both severe and long lasting. In some cases, administration of antivenom (or antivenin) can dramatically relieve pain and other symptoms of envenomation, even after failure of other approaches such as opioids and muscle relaxants. While neurotoxic envenomation should prompt close respiratory monitoring, opioids should be administered if clinically indicated for pain relief. The histamine pathway's contributions to terrestrial envenomation symptoms create a role for antihistamines (e.g. diphenhydramine) in treating land-based bites and stings. NSAIDs have been reported useful in small case series of bites from spiders such as brown recluses and tarantulas. Preliminary evidence from animal models and case reports suggests a role for NSAIDs for scorpion envenomation. Case studies suggest that corticosteroids are occasionally useful for some centipede bites, especially in cases in which Wells' syndrome (eosinophilic cellulitis) develops.