The term scorpion is derived from the Latin word scorpio, which in turn comes from the Greek skorpios. Alacrán is the Spanish word from Arabic al`aqráb. In Nahuatl language, the term is colotl, which means monster.¹

Scorpion stings constitute a medical emergency because of the inoculation of toxins in the tissue, which causes a varied toxic syndrome. They affect several organs and systems, produce sympathetic and parasympathetic stimulation, and can lead to the patient´s death.²

Epidemiology

Scorpion sting global incidence is estimated at 1.5 million events with 2,600 fatal cases.³ Out of the 281 species in Mexico, only 12 of the genus Centruroides are of medical relevance. C. noxius in Nayarit, C. limpidus in Guerrero, Morelos, and Michoacán, C. infamatus in Guanajuato and Estado de México, C. elegans in Jalisco, C. tecomanus in Colima, C. suffusus in Durango and C. sculpturatus in Sonora.^4,5 Guanajuato has had an increase in the incidence of poisoning by scorpion sting since 2010 with 28,973 cases reported until 2019 with 43,913 cases.^6-14

Sting accidents increase in hot weather and at night.^2,15 There are two different brands of scorpion antidotes available in Mexico to treat them. One is produced by Laboratorios de Reactivos y Biológicos de México S.A. de C.V., Birmex^® under the name of “faboterápico polivalente antialacrán" (anti-scorpion polyvalent fabotherapic); the other is manufactured by Bioclon Institute under the Alacramyn^® brand. Both neutralize an LD50 (150 per vial) and are obtained from hyperimmunized horses serum and a venom mixture of C. noxius, C. limpidus, and C. suffusus.^16-18

According to NOM-033-SSA2-2011, the following reference scheme is used for the surveillance, prevention, and control of scorpion sting poisoning, in poisonings in adults¹⁹:

• Grade 1 or mild, 1 dose,
• Grade 2 or moderate, 2 to 5 doses,
• Grade 3 or severe, 10 doses.

Treatment should begin within the first 30 minutes after the bite.² Antivenom application is more favorable against the scorpion sting than not doing it²⁰, regardless of price.²¹

It has been reported the application of up to ten doses of Birmex®²², while with Alacramyn^® is three maximum doses with an average hospital stay of 1 hour with mild symptoms and 3 with severe symptoms.²⁰

Care Costs

Direct costs such as medical fees, medications, studies, rehabilitation services, transportation, and supplies acquisitions for treatment must be considered to calculate the care cost; as well as indirect costs, which are the monetary cost of lost work time and psychic costs, which the user invests in the process of seeking and monitoring medical care.²³

In 1999, the average cost of the Alacramyn^® antidote, infusion equipment, parenteral solutions, antihistamines, steroids, and medical fees was measured, ranging from $ 500.00 to $ 600.00 pesos.²⁴

A study carried out in eight rural areas of Amatlán de las Cañas (Nayarit, Mexico) during 1995, evaluated two treatment schemes and the direct and indirect costs of the scorpion sting. Scheme A comprised public transportation, a day's salary, and meals for the patient; thus, the estimate was $ 148.50 pesos. Scheme B included taxi transfer, companion and patient working hours, companion and patient meals, at the cost of $ 395.50 pesos.²⁵ The cost of using home remedies is not considered.²⁶

In the 2016-2017 consolidated purchase, the antivenom cost was $ 210.12 pesos with a discount rate of 2.58% in Birmex^®, and 0.54% for Alacramyn^®. In 2017-2018, the cost was $ 212.48 pesos with a discount of 14.34% in Birmex^® and 0.01% in Alacramyn^®. Finally, in 2018-2019 the price was $ 182.01 pesos for both, offering a discount of 10.80% Birmex^® and 3.30% on Alacramyn^®.^27-29 This study aimed to compare both products costs in patients with scorpion sting poisoning.

A retrospective, descriptive, cost-minimization study in patients poisoned by scorpion sting at Cruz Roja Mexicana, Delegación León, from January 1^st, 2016 to December 30^th, 2019. The general practitioners divided the digital files into Alacramyn^® (n = 5,390) and Birmex^® (n = 4,039) groups.

The protocol was approved by the Ethics Committee from Cruz Roja Mexicana I.A.P. Delegación León, Guanajuato. The CHEERS (Consolidated Health Economic Evaluation Reporting Standards) checklist was used.³⁰

Price Estimation

The costs of the Goods Acquired in the Consolidated Purchase 2018-2019 of the IMSS were used. The antivenom vial cost was $ 182.01 pesos for Birmex^® (with a discount rate of 10.80%) and $ 182.01 pesos for Alacramyn^® (with a discount rate of 3.30%).²⁷

Statistic Analysis

The normality of the variables was checked with the Kolmogorov-Smirnov test. Nominal variables were presented in frequencies and percentages; quantitative variables were presented as means with their standard deviation. An analysis of variance (ANOVA) was used for the analysis between groups. The student's t-test was performed for the comparison of means. A p <0.05 was considered significant, estimating 95% confidence intervals. The statistical program SPSS version 21 was used for data analysis.

In total, 9,459 users treated for scorpion sting poisoning were analyzed. For the Birmex^® group (n = 4,039) 2,097 men (51.91%) and 1,942 women (48.08); mean age was 31.13 ± 18.10 (range: 1 year to 97 years). The Alacramyn^® group (n = 5,390) with 2,874 men (53.32%) and 2,516 women (46.67%); mean age 31.99 ± 17.94 years (range: 1 year to 91 years). The other sociodemographic data are shown in Table 1.

Supplies

Based on the materials required, the direct cost per patient for applying Fragments F (ab) '2 of polyvalent anti-scorpion immunoglobulin is the following: alcoholated swabs (3 pieces) $ 1.11, physiological solution 100 ml (1 piece): $ 14.21, insyte (1 piece) : $ 4.1, venoclysis equipment (1 piece): $ 4.11, syringe 20 ml (1 piece): $ 2.17, mouthwash (1 piece): $ 0.2, emergency medical fees: $ 833.00.²⁷ For a total cost of $ 858.92 pesos in direct costs derived from care.

Antivenom

For the Birmex^® group, 13,356 vials were used at the cost of $ 2,430,925.56, whereas for Alacramyn^®, a total of 10,170 vials and the cost was $ 1,834,842.81 (Student's t, p = 0.001). The use of vials and costs by age groups are shown in Table 2.

Time Elapsed from the Sting to Hospitalization

The mean sting at hospitalization for all subjects was 127.58 ± 64.97 min; for Birmex^®, it was 127.62 ± 64.92 min; for the Alacramyn^® group, it was 127.60 ± 64.98 min. A comparison analysis of means (Student T) between both groups did not show a significant difference (p = 0.942).

Intoxication Grade

The patients included in the study were classified as grade 1, grade 2, and grade 3. The Birmex^® group had 2,262 (56%) grade 1; 1,685 (41.72%) grade 2; and 91 (2.25%) grade 3. The patients treated with Alacramyn^® were 2,513 (46.62%) grade 1; 2,683 (49.78%) grade 2; and 194 (3.6%) grade 3. The classification of intoxication grade by age groups is found in Table 2. The analysis of variance (ANOVA) did not have a statistical significance p = 0.17.

Hospital Stay Time

Hospital time was 240.08 ± 69.74 min for the Birmex^® group, with a minimum hospital stay of 120 minutes; for the Alacramyn^® group, 131.73 ± 51.25 min, with a minimum of 45 minutes. The comparison of means had a statistical significance of p = 0.001.

Adverse Events

No user died, and no adverse effects or secondary reactions were reported while they were hospitalized.

Poisoning by scorpion sting is a public health problem requiring greater epidemiological surveillance in the places with the highest incidence. Due to the clinical condition it causes, it is necessary to train the personnel who attend these cases in the first line (paramedics, general practitioners, nurses) to provide better quality care and have better epidemiological knowledge.

The clinical practice guideline describes the number of vials to be administered according to the degree of poisoning by scorpion sting and the signs and symptoms that the patient present. However, in other publications it has been mentioned that the use of Birmex^® and Alacramyn^® as a treatment is different with respect to the number of vials administered, which is not mentioned or described in the clinical practice guidelines.

The dose and hospital time were considerably higher in the Birmex^® group, which has a different impact on the use of both antidotes in scorpion sting poisoning.

Our study's limitations are the absence of indirect costs for a better estimate of the total cost of care for scorpion sting poisoning, not being a randomized study, and not having had both products during the entire data collection period.

Nevertheless, the information presented on the administered doses of both products and the hospital stay can be used to design future studies.