Management of Brown Recluse Spider Bites in Primary Care

James W. Mold; David M. Thompson

doi:10.3122/jabfm.17.5.347

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Table 1.

Baseline Characteristics of Enrolled Patients (N = 256)

Characteristic	Percentage
Age group
0 to 9	5
10 to 19	12
20 to 44	45
45 to 64	31
≥65	7
Gender
Male	38
Female	62
Spider identified by credible witness or clinician	13
Brown recluse spiders seen in vicinity	57
Season when bite occurred
Winter	9
Spring	37
Summer	40
Fall	14
Place where bite occurred
Indoors	56
Outdoors	20
No idea	24
Location of bite
Arm	27
Leg	45
Trunk	19
Head	9
Severity (clinician rating)
Mild	34
Moderate	56
Severe	10
Initial probability that lesion was brown recluse spider bite
Possible	28
Probable or definite	72
Previous brown recluse bite	12
Diabetes mellitus	5
Use of NSAID at time of bite	7
Patient felt the bite when it occurred	15
Local symptoms/signs at enrollment
Pain	66
Itching	64
Tenderness	75
Blister or vesicles	29
Necrosis	39
Systemic symptoms/signs at enrollment
Symptoms	28
Signs	14

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Table 2.

Study Population by Treatment Group Showing Mean (S.D.) Baseline Severity and Outcomes for Each (N=189)

Treatments P-value for between Group Differences	Erythema Diameter (cm)	Necrosis Diameter (cm)	Healing Time (from Time of Bite in Days)	Percentage Resulting in Scarring
Conservative^*
Yes (N = 121)	5.8(5.3)	0.39(0.71)	23.0(20.9)	23.0
No (N = 68)	5.6(5.5)	0.34(0.66)	20.5(14.7)	17.5
P value	.76	.61	.36	.36
Meat tenderizer
Yes (N = 4)	4.0(1.7)	0.63(1.3)	6(1.4)	0
No (N = 185)	5.7(5.4)	0.36(0.72)	21.8(17.9)	20.2
P value	.13	.70	.21	.61
Antihistamine
Yes (N = 56)	6.8(5.9)	0.25(0.74)	19.0(13.6)	7.3
No (N = 133)	5.4(5.2)	0.39(0.72)	22.4(18.9)	23.8
P value	.09	.19	.20	.02
Dapsone
Yes (N = 42)	6.7(5.5)	0.42(1.0)	25.0(13.5)	29.0
No (N = 147)	5.5(5.4)	0.35(0.65)	21.0(18.6)	18.3
P value	.19	.69	.15	.17
DC Current
Yes (N = 6)	6.6(4.2)	0.75(0.88)	28.2(27.1)	16.7
No (N = 183)	5.7(5.4)	0.35(0.72)	21.4(17.5)	20.2
P value	.69	.19	.57	.83
High-dose Vitamin C
Yes (N = 14)	6.8(5.8)	0.38(0.60)	29.8(23.7)	44.5
No (N = 175)	5.6(5.4)	0.36(0.74)	21.2(17.5)	18.9
P value	.43	.94	.16	.06
Systemic corticosteroids
Yes (N = 76)	6.0(6.0)	0.28(0.59)	24.9(19.0)	17.0
No (N = 113)	5.6(5.2)	0.40(0.78)	20.3(17.3)	21.5
P value	.55	.17	.12	.49
Local injection corticosteroids
Yes (N = 13)	3.6(2.1)	0.29(0.31)	19.8(11.6)	30
No (N = 176)	5.8(5.5)	0.37(0.74)	21.8(18.2)	19.5
P value	.002	.40	.73	.42
Topical corticosteroids
Yes (N = 12)	3.7(2.7)	0.08(0.13)	17.9(12.6)	10.0
No (N = 177)	5.8(5.5)	0.38(0.74)	21.9(18.1)	20.7
P value	.02	<.0001	.50	.41
Systemic antibiotics
Yes (N = 152)	6.0(5.5)	0.42(0.78)	21.8(15.0)	21.4
No (N = 37)	5.3(5.2)	0.28(0.64)	21.4(21.5)	18.1
P value	.31	.11	.87	.58
Topical antibiotics
Yes (N = 50)	5.4(3.9)	0.51(0.81)	22.7(23.1)	26.3
No (N = 139)	6.2(5.8)	0.32(0.64)	21.4(16.3)	18.5
P value	.32	.20	.75	.28
Topical nitroglycerine
Yes (N = 24)	6.7(4.8)	0.34(0.61)	24.2(19.4)	28.6
No (N = 165)	5.6(5.5)	0.37(0.74)	21.3(17.7)	19.0
P value	.30	.87	.49	.30

* Conservative treatment included any one or more of the following: expectant observation, cool compresses, elevation, exercise avoidance, immobilization, and/or cleansing.

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Table 3.

Multivariate Models for the Two Outcome Measures Treatment Options Considered As Independent Variables (N = 174)

Variables	Lη Heal Time^* β (95% CI)	Scarring Odds Ratio (95% CI)
Dapsone	0.37(0.05,0.70)	4.27(1.05,17.44)
Systemic corticosteroids	0.25(0.004,0.50)	NS
Erythema diameter (cm)	0.02(0.004,0.04)	NS
Necrosis (yes/no)	NS	4.60(1.69,12.53)
Severity (severe)	NS	7.45(2.12,26.14)
Treatment delay (days)	0.08(0.05,0.11)	NS
Age	0.010(0.004,0.02)	NS
Diabetes mellitus	0.55(0.08,1.01)	NS