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Snakebite envenomation (SBE) is a public health issue in sub-Saharan countries. Antivenom is the only etiological treatment. Excellent tolerance is essential in managing SBE successfully. This study aimed to evaluate tolerance of InoserpTM PAN-AFRICA (IPA). It was conducted on fourteen sites across Cameroon. IPA was administered intravenously and repeated at the same dose every two hours if needed. Early and late tolerance was assessed by the onset of clinical signs within two hours and at a visit two weeks or more after the first IPA administration, respectively. Over 20 months, 447 patients presenting with a snakebite were included. One dose of IPA was administered to 361 patients and repeated at least once in 106 patients. No significant difference was shown between the proportion of adverse events in patients who received IPA (266/361, 73.7%) and those who did not (69/85, 81.2%) (p = 0.95). Adverse reactions, probably attributable to IPA, were identified in four (1.1%) patients, including one severe (angioedema) and three mild. All these reactions resolved favorably. None of the serious adverse events observed in twelve patients were attributed to IPA. No signs of late intolerance were observed in 302 patients. Tolerance appears to be satisfactory. The availability of effective and well-tolerated antivenoms would reduce the duration of treatment and prevent most disabilities and/or deaths. [ABSTRACT FROM AUTHOR]

Background: Snakebites is a serious public health issue but remains a neglected tropical disease. Data on antivenom effectiveness are urgently needed in Africa. We assessed effectiveness of Inoserp PAN-AFRICA (IPA), the recommended antivenom available in Cameroon. Methodology/Principal findings: We enrolled 447 patients presenting with snakebite in 14 health facilities across Cameroon. At presentation, cytotoxicity, coagulation troubles and neurotoxicity were graded. We administered two to four vials of antivenom to patients based on hemotoxic or neurotoxic signs. We renewed antivenom administration to patients with persistence of bleedings or neurotoxicity 2 hours after each injection. We defined early improvement as a reduction of the grade of envenomation symptoms 2 hours after first injection. Medium-term effectiveness was investigated looking at disappearance of symptoms during hospitalization. After hospital discharge, a home visit was planned to assess long-term outcomes. Between October 2019 and May 2021, we enrolled 447 (93.7%), including 72% from the savannah regions. The median [IQR] age was 25 [14–40]. Envenomation was diagnosed in 369 (82.6%) participants. The antivenom was administered to 356 patients (96.5%) of whom 256 (71.9%) received one administration. Among these patients, cytotoxic symptoms were observed in 336 (94.4%) participants, coagulation disorders in 234 (65.7%) participants and neurotoxicity in 23 (6.5%) participants. Two hours after the first administration of antivenom, we observed a decrease in coagulation disorders or neurotoxicity in 75.2% and 39.1% of patients, respectively. Complete cessation of bleedings and neurotoxicity occurred in 96% and 93% of patients within 24 hours, respectively. Sequelae have been observed in 9 (3%) patients at the home visit 15 days after hospital admission and 11 (3%) died including one before antivenom injection. Conclusions/Significance: We confirmed good effectiveness of the IPA and highlighted the rapid improvement in bleeding or neurotoxicity after the first administration. Sequential administrations of low doses of antivenom, rigorously assessed at short intervals for an eventual renewal, can preserve patient safety and save antivenom. Trial registration: NCT03326492. Author summary: Snakebite envenomation is a public health issue in all sub-Saharan countries. Their management remains a challenge due to the high cost of antivenom and complex treatment-seeking behavior. The objective of this study was to evaluate the tolerance and effectiveness of a commonly used antivenom in Cameroon, in 14 sites representative of the diversity of common epidemiological situations in sub-Saharan Africa. The treatment protocol was that recommended by the Cameroonian Ministry of Health. We reported in the present manuscript results on antivenom effectiveness. Administration of IPA (at least two vials) was decided in all patients presenting with any symptoms of envenomation (cytotoxicity, bleeding, neurotoxicity) regardless of severity. Two to four vials of antivenom were administered to patients depending on whether they had coagulopathy or neurotoxic disorders, respectively. We repeated the administration of antivenom at the same dose to patients if hemorrhagic or neurotoxic signs persisted 2 hours after each injection. During 20 months, we examined 477 patients and enrolled 447 (94%). Three hundred fifty-six patients presenting envenomation signs have received at least one dose of antivenom. Envenomation was diagnosed in 369 (83%) participants, out of which, 9 (3%) kept sequelae of varying severity, and 11 (3%) died, including one before the antivenom injection. Cytotoxic symptoms were observed in 336 (94.4%) participants, coagulation disorders in 234 (65.7%) participants and neurotoxic syndrome in 23 (6.5%) participants. A single antivenom administration was performed for 256 (71.9%) patients. Two hours after the first administration of antivenom, coagulation disorders and neurotoxicity decreased in 75.2% and 39.1% of patients, respectively. Complete stop bleedings and neurotoxicity occurred in 96% and 93% of patients within 24 hours, respectively. We confirmed the good effectiveness of IPA and highlighted the rapid improvement in bleedings or neurotoxicity after its first administration. [ABSTRACT FROM AUTHOR]