Non-clinical evidence supports anti-inflammatories as more effective medication than antihistamines against tarantula local effects envenomation

Abstract

Background: Tarantulas are the most common invertebrates pets, especially in North America and Europe. The most commercialized genera are from Southern Asia and tropical Americas, represented by Vitalius, found in Southeastern Brazil, and Brachypelma, common in Mexican desert. Bites by these spiders in humans occurs during manipulation and generally result in clinical manifestations such local pain, erythema and oedema, with the possibility of secondary local infection. Hence, the cases are usually treated with prescription free drugs such as antihistamines and anti-inflammatories. Methods: In this work, we investigated the post treatment with commercial nonsteroidal and steroidal anti-inflammatories and anti-histamines administered by oral and intraperitoneal routes on rat paw oedema induced by venoms of V. dubius and B. smithi. Hydroplethysmometer standard oedema measurement and Evans blue extravasation were performed. Dose standardization experiments showed that the V. dubius is more potent than B. smithi, and doses were established at 30 μg/paw and 60 μg/paw respectively. Results: The oral post-administration of ketoprofen (non-selective cyclooxygenase inhibitor) and prednisolone (steroidal anti-inflammatory) markedly reduced a paw oedema evoked by only V. dubius venom, but loratadine (H1-antihistamine) had negligible effect on rat paw oedema induced by both venoms. Intraperitoneal administration, ketoprofen (20 mg Kg-1) and loratadine (5 mg Kg-1) reduced the rat paw oedema induced by V. dubius and B. smithi while methylprednisolone (10 mg Kg-1) only inhibited the oedema induced by V. dubius. Conclusion: These results suggest that the pos-treatment with nonsteroidal and steroidal anti-inflammatory drugs are more potent than antihistamines in attenuating the local effect induced by V. dubius and B. smithi venoms.