Safety and cost-effectiveness of a clinical protocol implemented to standardize the use of Crotalidae polyvalent immune Fab antivenom at an academic medical center

Chronic health effects and cost of snakebite

The burden of disability among survivors and the socio-economic impact of snakebite have not been adequately researched. We reviewed original research articles, case reports and small case series relating to chronic physical, mental and psycho-social disability and economic burden of snakebite. Both physical and psychological health problems seem common in snakebite survivors and can lead to disability and loss of productivity. Chronic physical health effects, musculoskeletal disability being the commonest, can be largely attributed to limited and delayed access to optimal treatment of acute envenoming. The economic burden is considerable, and includes health system costs, out-of-pocket expenditure and opportunity costs, with regional variations. Health systems should be more responsive to needs and circumstances of bite victims, and a more holistic approach should be developed in the treatment of snakebite which incorporates the management of chronic health effects.

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Limited attention has been paid to chronic disability and the socio-economic impact of snakebite.

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Physical and psychological health problems occur in snakebite survivors leading to disability and loss of productivity.

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Chronic health effects can be largely attributed to limited and delayed access to optimal treatment of acute envenoming.

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Economic burden includes health system costs, out-of-pocket expenditure and opportunity costs.

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Health systems should be responsive to needs and circumstances of bite victims including care of chronic health effects.

Review of North American pit viper antivenoms

PURPOSE

For the first time in nearly 20 years, 2 antigen-binding fragment (Fab) antivenoms are available to treat patients who incur North American pit viper snakebites: Crotalidae polyvalent immune Fab (ovine), or simply FabAV; and Crotalidae immune F(ab')2 (equine), or simply F(ab')2. Pharmacists are in a key position for the selection, dosing, reconstitution, administration, and monitoring of antivenom therapy; however, they encounter inconsistent exposure and experience with these drugs. Thus, an updated review of the literature is necessary.

METHODS

The search strategy and selection incorporated both controlled vocabulary terms and keywords to describe concepts relevant to the search. Retrieval was limited to literature published from 1997 to the present in English, Portuguese, or Spanish.

RESULTS

Given the paucity of available prospective literature, the authors elected to include all prospective evidence to best describe the role of antivenom. For the primary literature review, manuscripts were excluded if they were observational studies, conference abstracts, narrative or opinion articles, letters to the editor, or in-progress studies.

CONCLUSION

While there is limited evidence-based guidance on the superiority of F(ab')2 to FabAV, or vice versa, individual and regional considerations should contribute to formulary decisions. Pharmacists must play a role in the development of clinical pathways to ensure appropriate evaluation, supportive care, and antivenom procurement, administration, and monitoring.

Economic Evaluations of Interventions for Snakebites: A Systematic Review

Background

Snakebite is an often-neglected event with a high rate of mortality and is concentrated in poor areas. We aimed to assess the economic impact and health effects of the implementation of interventions for snakebites through a systematic review of the scientific literature.

Methods

Thirty search strategies were conducted in seven databases, applying PRISMA’s identification, screening, selection, and inclusion phases. The reproducibility of the selection of studies and the extraction of information were guaranteed. The methodological quality was evaluated using the Consolidated Health Economic Evaluation Reporting Standards. Qualitative synthesis and meta-analysis were performed for determining the average cost-effectiveness (ACE) for each death and disability-adjusted life years (DALY) avoided.

Results

Six cost-effectiveness studies were included for the supply of antivenom (AV), taken as outcomes on days of hospitalization or in ICU, death and DALYs avoided. All studies only included institutional costs, and majority of them did not specify the analytical model or economic evaluation parameters and did not perform uncertainty analyses. The management protocol standardization with interdisciplinary attention improves ACE of AV. Cost-effectiveness ratio (CER) of treatment with AV was USD 1253 (constant value for the year 2017, adjusted by purchasing power parity) for each death avoided and USD 51 per DALY avoided.

Conclusion

High cost-effectiveness of the AV treatment for snakebites was evidenced, which shows that the allocation of resources for this event should be a healthcare priority in addition to implementation of strategies that improve the access to, opportunity, and quality of hospital and pre-hospital care and reduce the cost of AV.

Early administration of Fab antivenom resulted in faster limb recovery in copperhead snake envenomation patients

BACKGROUND

No previous research has studied whether early snake antivenom administration leads to better clinical outcomes than late antivenom administration in North American pit viper envenomation.

METHODS

A secondary analysis of data from a clinical trial of Fab antivenom (FabAV) versus placebo for copperhead snake envenomation was conducted. Patients treated before the median time to FabAV administration were classified as receiving early treatment and those treated after the median time were defined as the late treatment group. A Cox proportional hazards model was used to compare time to full recovery on the Patient-Specific Functional Scale (PSFS) instrument between groups. Secondary analyses compared estimated mean PSFS scores using a generalized linear model and the estimated proportion of patients with full recovery at each time point using logistic regression. To evaluate for confounding, the main analysis was repeated using data from placebo-treated subjects.

RESULTS

Forty-five subjects were treated with FabAV at a median of 5.47 h after envenomation. Patients in the early treatment group had a significantly shorter time to full recovery than those treated late (median time: 17 versus 28 days, p = .025). Model-estimated PSFS scores were numerically higher at each time point in the early group. No difference was found between patients treated early versus late with placebo.

CONCLUSIONS

In this secondary analysis of trial data, recovery of limb function was faster when Fab antivenom was administered soon after envenomation, as opposed to late administration.

Resource Utilization After Snakebite Severity Score Implementation into Treatment Algorithm of Crotaline Bite

BACKGROUND

Crotaline envenomation clinical manifestations vary considerably among patients. Current recommendations for treatment with Crotalidae polyvalent immune Fab require assessment of envenomation control. Determining control of envenomation, particularly when patients are evaluated by different providers in separate clinical settings, can be difficult.

OBJECTIVE

To determine if a difference in total vials of Crotalidae antivenin therapy exists between pre-protocol and post-Snakebite Severity Score (SSS) protocol.

METHODS

Retrospective medical record review at an academic medical and regional Level I trauma center. Resource utilization in patients with a diagnosis of "snakebite" was compared between patients treated pre- and post-SSS protocol implementation.

RESULTS

One hundred forty-six patients were included in the evaluation. One hundred twenty-seven (87.0%) patients received antivenin, n = 80 (90.9%) in the pre-protocol group and n = 47 (81.0%) in the post-protocol group. Median total number of antivenin vials per patient was lower in the post-protocol group than the pre-protocol group, 16 (10-24 interquartile range) vs. 12 (10-16 interquartile range), p = 0.006. This decreased utilization correlates to an approximate $13,200 savings per patient. Hospital and intensive care unit length of stay, opioid use, incidence of blood product transfusion, need for surgical intervention, or need for intubation were not different between groups.

CONCLUSIONS

A snakebite protocol with SSS utilization to guide antivenin administration results in significantly decreased antivenin therapy in snakebite patients without increase in other health care utilization.

Benefits of using heterologous polyclonal antibodies and potential applications to new and undertreated infectious pathogens

BACKGROUND

Passive immunotherapy using polyclonal antibodies (immunoglobulins) has been used for over a century in the treatment and post-exposure prophylaxis of various infections and toxins. Heterologous polyclonal antibodies are obtained from animals hyperimmunised with a pathogen or toxin.

AIMS

The aims of this review are to examine the history of animal polyclonal antibody therapy use, their development into safe and effective products and the potential application to humans for emerging and neglected infectious diseases.

METHODS

A literature search of OVID Medline and OVID Embase databases was undertaken to identify articles on the safety, efficacy and ongoing development of polyclonal antibodies. The search contained database-specific MeSH and EMTREE terms in combination with pertinent text-words: polyclonal antibodies and rare/neglected diseases, antivenins, immunoglobulins, serum sickness, anaphylaxis, drug safety, post marketing surveillance, rabies, human influenza, Dengue, West Nile, Nipah, Hendra, Marburg, MERS, Hemorrhagic Fever Virus, and Crimean-Congo. No language limits were applied. The final search was completed on 20.06.2015. Of 1960 articles, title searches excluded many irrelevant articles, yielding 303 articles read in full. Of these, 179 are referenced in this study.

RESULTS

Serum therapy was first used in the 1890s against diphtheria. Early preparation techniques yielded products contaminated with reactogenic animal proteins. The introduction of enzymatic digestion, and purification techniques substantially improved their safety profile. The removal of the Fc fragment of antibodies further reduces hypersensitivity reactions. Clinical studies have demonstrated the efficacy of polyclonal antibodies against various infections, toxins and venoms. Products are being developed against infections for which prophylactic and therapeutic options are currently limited, such as avian influenza, Ebola and other zoonotic viruses.

CONCLUSIONS

Polyclonal antibodies have been successfully applied to rabies, envenomation and intoxication. Polyclonal production provides an exciting opportunity to revolutionise the prognosis of both longstanding neglected tropical diseases as well as emerging infectious threats to humans.

Effectiveness of a clinical protocol implemented to standardize snakebite management in Iran: initial evaluation

OBJECTIVE

This study was designed to evaluate the effectiveness of a new protocol implemented to standardize snakebite management in Iran.

METHODS

In this study, 27 patients treated according to the new protocol in 2012 (P+) were compared with 22 patients treated according to the previous modality in the year before implementation of the protocol (P-) in Mashhad Medical Toxicology Centre (MTC). Demographic characteristics and treatment details of all patients were recorded prospectively. Envenomation severity of each victim was assessed according to snakebite severity score (SSS).

RESULTS

After implementation of the protocol, a smaller percentage of patients received antivenom (AV) therapy (78% vs 95%; P=.079). In spite of no significant difference in baseline severity of envenomation between the 2 groups (SSS [mean±SD], 34.8±18.1 vs 35.5±17.4; P=.801), the P+ group received significantly fewer AV vials (8.4±6.8 vs 12.1±5.6 vials; P=.042) and had a significantly shorter length of hospital stay (2.2±1.5 vs 3.2±1.8 days; P=.027). Moreover, smaller proportion of P+ patients experienced recurrence of venom-induced effects; however, the difference was not significant (18.5% vs 36%; P=.159). The reduction in use of antiallergy treatments to prevent or treat acute hypersensitivity reactions approached statistical significance (41% vs 68%; P=.051). These findings denote a reduction in AV use of approximately 4 vials and a reduction in hospital stay of 1 day for each patient, which translates to approximately $196/patient in healthcare cost savings.

CONCLUSIONS

Implementation of a snakebite management protocol at MTC reduced overall antivenom usage, use of antiallergy interventions, and length of hospital stay.

Ethical considerations in design of a study to evaluate a US Food and Drug Administration–approved indication: Antivenom versus placebo for copperhead envenomation

Background:

In 2000, the US Food and Drug Administration approved CroFab® Crotalidae Polyvalent Immune Fab, ovine (FabAV), which had received orphan drug designation, for use in patients with minimal to moderate North American crotaline envenomations including copperhead snakes. As existing evidence on the effectiveness of FabAV for this indication is limited, wide practice variation in its use exists. In order to provide more definitive clinical evidence as to the role of this treatment, a new randomized, placebo-controlled trial of FabAV specifically for copperhead bites was initiated.

Purpose:

In light of the existing US Food and Drug Administration approval, ethical considerations of participation in this trial have been raised. We discuss the ethical principles pertinent to this randomized, placebo-controlled trial with placebo arm. We apply an accepted framework for ethical research to this trial. Due to the evidence gap in the literature, wide-ranging treatment recommendations by medical experts, and broad practice variation, clinical equipoise exists in the treatment of copperhead envenomation with FabAV. The impact of this clinical equipoise on the value and scientific validity of the trial is discussed. The trial’s risk–benefit ratio is also considered. Potential risks to the patients are minimized as the protocol includes a plan for rescue therapy in the event that patients progress to severe envenomation symptoms. Overall, risks are further minimized by the inclusion of an interim analysis with stopping rules based on demonstrated efficacy should the therapy clearly prove to be beneficial.

Conclusion:

Although a post-marketing clinical study of this nature is unusual for an approved indication, this trial adheres to all ethical preconditions found in existing guidelines for clinical research involving human subjects.

National survey of pharmacy residency on-call programs

PURPOSE

The results of a national survey to evaluate on-call practices and responsibilities of pharmacy residents nationwide, as well as opinions related to duty-hour changes, are reported.

METHODS

A 39-question survey was distributed to 1292 residency program directors (RPDs) listed in the American Society of Health-System Pharmacists (ASHP) online residency directory, which includes programs in all stages of the accreditation process. The survey opened on November 7, 2011, and closed on November 28, 2011. The survey collected demographic information and answers to questions about the residency's on-call component (if applicable) and barriers to the creation of an on-call component. Respondents were also asked to indicate their support of or opposition to the adoption of the 2011 Accreditation Council for Graduate Medical Education (ACGME) duty-hour rules and identify the areas of greatest concern.

RESULTS

Of the 1292 RPDs listed in the ASHP online residency directory to whom the survey was sent, 521 surveys were completed, yielding a response rate of 40%. Of these, 471 identified their residency program as including or excluding an on-call component. Of the 138 programs with on-call services, 102 programs (74%) indicated the inclusion of an overnight experience. Programs that did not utilize an on-call component indicated barriers such as a perceived lack of demand (39%) and duty-hour limitations (21%). Common on-call activities included drug information consults and therapeutic drug monitoring. There was not a clear consensus from RPDs regarding the adoption of the 2011 ACGME duty-hour standards.

CONCLUSION

Among usable responses to a survey of pharmacy residency programs, 29% indicated that their program included an on-call component. On-call programs varied greatly in activities, location, hours, and requirements.