Table 1.

Characteristics of cases for hospitalization for neurologic phenytoin toxicity and controls and results of multi-variable logistic regression models

	n (%)
	Cases N = 14	Controls N = 290
Recruitment source
PACE†	5 (35.7)	274 (94.5)
Geisinger Health System	9 (64.3)	16 ( 5.5)
Sex
Male	4 (28.6)	79 (27.2)
Female	10 (71.4)	211 (72.8)
Race
White	14 (100)	274 (94.5)
African American	0 ( 0.0)	13 ( 4.5)
Other	0 ( 0.0)	2 ( 0.7)
Unknown	0 ( 0.0)	1 ( 0.3)
Median age, in years (interquartile range)	68.4 (33.9)	76.3 (10.2)
Mean phenytoin concentration on admission‡, mg/L (standard deviation)	31.2 (12.9)	-
			Crude OR (95% CI)	Adjusted§ OR (95% CI)
Genotype
CYP2C9
*1/*1	8 (57.1)	194 (66.9)	1.00 (reference)	1.00 (reference)
*1/*2	4 (28.6)	89 (30.7)	1.09 (0.32–3.71)	0.96 (0.25–3.66)
*1/*3	1 (7.15)	4 ( 1.4)	6.06 (0.61–60.6)	8.91 (0.79–100)
*2/*2	1 (7.15)	3 ( 1.0)	8.08 (0.75–86.6)	9.48 (0.79–115)
*2/*3	0 ( 0.0)	0 ( 0.0)	-	-
*3/*3	0 ( 0.0)	0 ( 0.0)	-	-
CYP2C19
*1/*1	10 (71.4)	213 (73.5)	1.00 (reference)	1.00 (reference)
*1/*2	2 (14.3)	70 (24.1)	0.61 (0.13–2.84)	0.50 (0.09–2.73)
*1/*3	2 (14.3)	7 ( 2.4)	6.09 (1.12–33.1)	4.21 (0.58–30.8)
*2/*2	0 ( 0.0)	0 ( 0.0)	-	-
*2/*3	0 ( 0.0)	0 ( 0.0)	-	-
*3/*3	0 ( 0.0)	0 ( 0.0)	-	-
ABCB1
C/C	3 (21.4)	72 (24.8)	1.00 (reference)	1.00 (reference)
C/T	6 (42.9)	123 (42.4)	1.17 (0.28–4.82)	0.84 (0.18–3.81)
T/T	5 (35.7)	95 (32.8)	1.26 (0.29–5.46)	1.32 (0.28–6.18)

^†Pennsylvania Pharmaceutical Assistance Contract for the Elderly prescription drug program (including members of the Needs Enhancement Tier)

^‡Usual therapeutic range = 10 to 20 mg/L

^§Adjusted for age, sex, and number of variant alleles of other metabolic enzymes

OR = odds ratio; CI = confidence interval