Comparison of F(ab’)₂ versus Fab antivenom for pit viper envenomation: A prospective, blinded, multicenter, randomized clinical trial

Figures & data

Fig. 1. CONSORT flow diagram (colour version of this figure can be found in the online version at www.informahealthcare.com/ctx).

Table 1. Demographic and baseline characteristics of the patients.*

	F(ab’)2/F(ab’)2	F(ab’)2/Placebo	Fab/Fab
Variable	(N = 41)	(N = 40)	(N = 40)
Age – yr
Mean	32.9^†± 22.26	40.3 ± 21.02	45.6 ± 16.52
Median	36	43	48
Range	2–80	7–77	5–80
Age < 10 yrs – no. (%)	12^‡ (29.3)	5 (12.5)	1 (2.5)
Female gender- no. (%)	11 (26.8)	10 (25.0)	12 (30.0)
Ethnicity- no. (%)
White	29 (70.7)	31 (77.5)	26 (65.0)
Hispanic	8 (19.5)	7 (17.5)	10 (25.0)
Black	3 (7.3)	1 (2.5)	2 (5.0)
Native American	1 (2.4)	1 (2.5)	2 (5.0)
Baseline platelet count – K/mm^3
Mean	197.1 ± 100.7	223.6 ± 85.7	189.5 ± 79.3
Median	185.5	221.0	199.5
Range	15–400	26–382	35–348
Baseline fibrinogen level – mg/dL
Mean	275.8 ± 129.2	276.5 ± 98.5	268.4 ± 86.6
Median	256.0	293.0	267.0
Range	60–718	20–475	60–438
Snakebite Severity Score^Citation31
Mean	3.8 ± 2.10	3.0 ± 1.51	3.8 ± 2.33
Median	3.0	3.0	3.0
Range	1–11	1–7	1–11
Bite-to-antivenom start time – hrs
Mean	6.4 ± 6.22	4.9 ± 3.44	8.7 ± 10.93
Median	4.4	3.5	4.5
Range	2.1–35.5	1.8–18.7	1.6–58.7

*Plus-minus values are means± SD.

^†p < 0.05, One-way ANOVA, compared with Fab/Fab.

^‡p < 0.05, Fisher's exact test, compared with Fab/Fab.

Table 2. Efficacy endpoints.

	F(ab’)2/F(ab’)2 (N = 39)	F(ab’)2/placebo (N = 38)	Fab/Fab (N = 37)
Experienced late coagulopathy—No. (%)	4 (10.3)^‡	2 (5.3)^‡	11 (29.7)
Absolute risk reduction (95% Cl)*	0.195 (0.014–0.367)	0.245 (0.073–0.410)	−
Number needed to treat (patients)*	Approximately 5	Approximately 4	–
Mean platelet count, 1,000 s per mm ± SD (range)
Day 5	265.2 ± 81.4 (121–434)	259.5 ± 61.4 (132–374)	227.1 ± 70.0 (77–389)
Day 8	266.8 ± 84.7 (125–447)	265.0 ± 73.5 (114–424)	234.1 ± 80.8 (40–415)
Mean fibrinogen, mg/dL ± SD (range)
Day 5	369.4 ± 75.1 (223–530)	394.7 ± 97.7 (173–650)	364 ± 116.5 (81–564)
Day 8	344.7 ± 70.9 (208–477)	387.1 ± 96.0 (195–693)	334.8 ± 114.4 (105–589)
Lowest platelet count, 1,000 s per mm^3 ± SD (range)
	253.4^†± 80.3 (121–434)	247.5^†± 62.6 (114–374)	208.9 ± 76.9 (40–389)
Lowest fibrinogen, mg/dL ± SD (range)
	340.0 ± 70.0 (208–477)	367.8^†± 93.9 (173–650)	309.0 ± 116.4 (< 60–564)

*Compared with Fab/Fab .

^†p < 0.05, One-way ANOVA, compared to Fab/Fab.

^‡p < 0.05, Fisher's exact test, compared to Fab/Fab.

Table 3. Adverse events (Safety population).

Event	F(ab’)2/F(ab’)2* (N = 43)	F(ab’)2/Placebo* (N = 37)	Fab/Fab (N = 41)
Number of AEs	130	72	137
Patients reporting at least 1 AE—No. (%)	35 (81.4)	24 (64.9)	33 (80.5)
Itching (pruritus)—No. (%)	20 (46.5)	14 (37.8)	20 (48.8)
Easy bruising, gingival bleeding, petechiae or melena—No. (%)	4 (9.3)	3 (8.1)	10 (24.4)
Nausea, vomiting—No. (%)	8 (18.7)	6 (16.2)	7 (17.0)
Rash —No. (%)	5 (11.6)	5 (13.5)	5 (12.2)
Arthralgia—No. (%)	4 (9.3)	4 (10.8)	7 (17.1)
Myalgia—No. (%)	3 (7.0)	3 (8.1)	8 (19.5)
Dehydration—No. (%)	2 (4.7)	0 (0.0)	4 (9.8)
Chest pain—No. (%)	0 (0.0)	1 (2.7)	2 (4.9)
Other (fever, headache, cellulitis, diarrhea, pain, fatigue or blisters)—No. (%)	18 (41.9)	11 (29.7)	17 (41.5)
Serious adverse events—No. (%)	6 (14.6)	1 (2.7)	2 (4.9)
Immune reactions
Acute serum reaction—No. (%)	1 (2.3)	1 (2.7)	1 (2.4)
Serum sickness—No. (%)	1 (2.3)	1 (2.7)	1 (2.4)

*No pairwise comparison with Fab/Fab was significant using Fisher's exact test.

Sanchez EE, Galan JA, Perez JC, Rodriguez-Acosta A, Chase PB, Perez JC. The efficacy of two antivenoms against the venom of North American snakes. Toxicon 2003; 41:357–365.

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