The Malayan pit viper (MPV: Calloselasma rhodostoma) is a medically important venomous snake causing numerous envenomations in Thailand. Administration of specific snake antivenom is the only effective treatment for MPV-envenomed patients. However, inappropriate administration or misuse of snake antivenom is problematic in some remote areas of tropical countries where the snakebite envenoming rate is notable. Currently, the indications for administration of MPV antivenom are focused mainly on hematological factors. These include 1) venous clotting time > 20 min, 2) unclotted 20-minute whole-blood clotting time, 3) international normalized ratio > 1.2, 4) platelet count < 50 × 10³/μL, 5) systemic bleeding, and 6) impending compartment syndrome. We aimed to determine the association between laboratory data and antivenom administration in MPV-envenomed patients. A retrospective study of data from 2016 to 2021 in Narathiwat Province, the southernmost province in Thailand, was conducted. A total of 838 MPV-bitten patients were included in this study. Local effects and systemic effects were observed in 58.8% and 27.7% of patients, respectively. Coagulopathies, which range from abnormal blood clotting to systemic bleeding, represented the majority of systemic effects. Acute kidney injury developed in 2.5% of patients. In this study, 57.3% of patients were considered appropriate antivenom recipients. Interestingly, the present study revealed that local bleeding and mild to moderate thrombocytopenia became the independent factors for inappropriate use of MPV antivenom. Reeducation and supervision regarding the rational use of snake antivenom are needed to minimize the misuse of antivenom.

Background: Cobras (Naja sp.) are medically important snakes in Thailand. Envenoming by the monocled cobra (N. kaouthia) often causes neurotoxicity, most notably ptosis, ophthalmoplegia, local tissue necrosis and progressive paralysis leading to respiratory failure. Early antivenom administration and respiratory support are medically significant for effective treatment. Methods: In this study, we determined the association between the time course of cobra envenoming and related neurotoxic outcomes using the clinical profiles of cobra envenomed patients. We also demonstrated histopathological changes in the neuromuscular junction of the diaphragm in experimentally envenomed rats. Results: A retrospective study of 69 cases of cobra envenoming in Central and Southern Thailand shows that delayed arrival beyond one hour at hospital was common among younger adults (47.0% aged 10–29) and associated with more severe neurotoxicity, including higher rates of ptosis (41.2%, p = 0.032) and referrals (41.2% vs. 15.4%, p = 0.040). Antivenoms (22 Monovalent and 1 Polyvalent) were administered to 23 (33.3%) envenomed victims and caused adverse reactions in 9 cases (39.1%). Neurotoxicity following cobra envenoming in the clinical section correlated with histopathological examination of envenomed rat diaphragms. Transmission electron microscopy (TEM) revealed degeneration of the neuromuscular junction and diaphragm within 1 h following experimental cobra envenomation, which worsened by 4 h. Intravenous administration of antivenom at recommended doses reduced diaphragmatic damage but failed to prevent presynaptic degeneration after 90 min of envenoming. Conclusions: Clinically, extraocular muscle paralysis was the earliest manifestation. Early monitoring and prompt administration of antivenom are essential to reduce neurotoxicity and relevant complications.

The administration of specific immunoglobulin G-based antivenoms is a key strategy for treating snakebite envenoming victims. However, serious adverse reactions, such as anaphylaxis or serum sickness, are frequently observed following such administration. In addition, inflammation associated with delayed wound healing considerably drives the irrational use of antibiotics or anti-inflammatory agents, which may be linked to adverse reactions following antivenom treatment. In this study, we evaluated the factors contributing to adverse effects following the administration of snake antivenom, especially pharmacological treatment and premedication intended to prevent adverse reactions. Our retrospective study was conducted by healthcare professionals in Narathiwat, the southernmost province in Thailand, and it involved 980 patients confirmed to have been snakebitten from 2016 to 2021. Of these cases, 513 were treated with antivenom. Prevalence rates and 95% confidence intervals were calculated, and univariate and multivariate analyses were performed to determine the correlation between adverse reactions and medications. Following antivenom administration, the majority of the patients exhibited no adverse reactions (86.7%). Nevertheless, skin rash, itching, wheezing, angioedema, chest tightness, and fever were observed in 13.3% of those receiving snake antivenom. After the administration of antivenom for Malayan pit viper bite, adverse reactions occurred in 11.7% of the sample, especially among referral patients (p < 0.001). Epinephrine and antihistamines were prescribed as prevention and treatment for hypersensitivity due to antivenom administration. Antibiotics, Non-steroidal Anti-inflammatory drugs (NSAIDs), and acetaminophen were not associated with antivenom-induced adverse reactions. Interestingly, tramadol and antihistamines significantly reduced the occurrence of adverse reactions after antivenom administration (p < 0.05). Well-trained staff, close monitoring alongside resuscitation equipment and medications that can minimise the severity of anaphylactic reactions must be promptly available whenever antivenom is administered.