Table 2.
Risk factor study—gabapentin: association between potential risk factors and adverse outcomes.
| Characteristics (n) | Misuse | Overdose | Trauma | |||
|---|---|---|---|---|---|---|
| Rate per 10,000 person-years (95% CI) | Hazard ratio* (95% CI) | Rate per 10,000 person-years (95% CI) | Hazard ratio* (95% CI) | Rate per 10,000 person-years (95% CI) | Hazard ratio* (95% CI) | |
| Age group (y) | ||||||
| 18-25 | 632.5 (604.4-661.9) | 105.9 (95.4-117.7) | 272.8 (255.0-297.9) | |||
| 25-34 | 610.3 (596.4-624.6) | 85.8 (80.9-90.9) | 221.1 (213.1-229.5) | |||
| 35-44 | 473.4 (465.5-481.5) | 61.9 (59.3-64.7) | 205.1 (200.1-210.3) | |||
| 45-54 | 443.5 (437.1-450.0) | 42.8 (41.0-44.8) | 226.8 (222.4-231.4) | |||
| 55-64 | 363.6 (357.8-369.4) | 26.2 (24.8-27.8) | 277.6 (272.6-282.7) | |||
| 65-74 | 266.5 (261.3-271.7) | 23.5 (22.0-25.1) | 391.6 (385.2-398.0) | |||
| ≥75 | 164.9 (160.5-169.5) | 29.5 (27.7-31.4) | 812.8 (802.2-823.5) | |||
| Sex | ||||||
| Female | 429.0 (424.3-433.8) | 40.0 (38.6-41.4) | 310.2 (306.2-314.3) | |||
| Male | 327.1 (323.9-330.3) | 40.3 (39.2-41.4) | 372.5 (369.1-376.0) | |||
| IMD fifth | ||||||
| 1 (least deprived) | 203.4 (198.9-208.0) | 26.9 (25.3-28.5) | 366.3 (360.1-372.6) | |||
| 2 | 263.7 (258.6-268.9) | 31.5 (29.8-33.3) | 359.7 (353.6-365.8) | |||
| 3 | 329.5 (323.7-335.4) | 37.3 (35.4-39.2) | 352.6 (346.6-358.7) | |||
| 4 | 421.8 (415.4-428.4) | 43.1 (41.2-45.1) | 335.6 (330.0-341.4) | |||
| 5 (most deprived) | 580.3 (573.0-587.6) | 58.4 (56.3-60.6) | 334.5 (329.2-340.0) | |||
| Body mass index† | ||||||
| Normal/underweight | 443.6 (438.0-449.3) | 1 | 45.8 (44.1-47.5) | 1 | 396.8 (391.5-402.1) | 1 |
| Overweight | 338.9 (334.4-343.5) | 0.72 (0.71-0.73) | 39.7 (38.2-41.2) | 0.91 (0.87-0.96) | 317.8 (313.4-322.2) | 0.82 (0.80-0.83) |
| Obese | 334.4 (329.9-339.0) | 0.77 (0.76-0.79) | 34.7 (33.4-36.2) | 0.85 (0.81-0.90) | 348.9 (344.3-353.6) | 0.84 (0.82-0.86) |
| Smoking status‡ | ||||||
| Current | 1076.2 (1067.0-1085.5) | 1 | 64.2 (62.2-66.2) | 1 | 314.4 (309.8-319.1) | 1 |
| Never | 61.0 (59.4-62.6) | 0.07 (0.07-0.07) | 28.4 (27.3-29.6) | 0.54 (0.51-0.57) | 347.1 (343.1-351.2) | 0.88 (0.86-0.89) |
| Previous | 242.0 (237.8-246.2) | 0.26 (0.26-0.27) | 32.7 (31.2-34.2) | 0.66 (0.62-0.70) | 392.6 (387.2-398.1) | 0.96 (0.94-0.98) |
| History of substance misuse | NA | |||||
| No | 40.0 (39.2-40.9) | 1 | 648.8 (346.2-351.5) | 1 | ||
| Yes | 138.5 (105.0-182.7) | 1.99 (1.51-2.63) | 368.6 (309.3-439.2) | 1.55 (1.30-1.84) | ||
| History of overdose§ | ||||||
| No | 358.4 (335.8-361.1) | 1 | 38.1 (37.3-39.0) | 1 | 348.0 (345.4-350.7) | 1 |
| Yes | 1214.1 (1158.6-1272.3) | 2.54 (2.42-2.66) | 281.7 (258.0-307.6) | 5.58 (5.09-6.12) | 443.9 (413.3-476.8) | 1.63 (1.52-1.75) |
| History of mental health condition | ||||||
| No | 297.2 (294.4-300.1) | 1 | 27.9 (27.1-28.8) | 1 | 340.3 (337.2-343.4) | 1 |
| Yes | 536.3 (530.2-542.5) | 1.68 (1.66-1.71) | 68.8 (67.8-72.0) | 2.31 (2.21-2.42) | 369.6 (364.6-374.6) | 1.22 (1.20-1.25) |
| Benzodiazepines‖ | ||||||
| No | 342.2 (339.4-345.0) | 1 | 32.9 (32.1-33.8) | 1 | 340.0 (337.3-342.8) | 1 |
| Yes | 528.5 (519.3-537.8) | 1.55 (1.52-1.58) | 90.6 (87.0-94.3) | 2.64 (2.51-2.77) | 410.4 (402.4-418.5) | 1.26 (1.23-1.28) |
| Nonbenzodiazepine hypnotics‖ | ||||||
| No | 348.7 (346.0-351.4) | 1 | 35.3 (34.5-36.1) | 1 | 342.5 (339.8-345.1) | 1 |
| Yes | 341.3 (626.3-656.7) | 1.81 (1.76-1.85) | 119.7 (113.7-126.0) | 3.21 (3.03-3.40) | 453.3 (441.0-466.0) | 1.34 (1.30-1.38) |
| Antidepressants‖ | ||||||
| No | 295.5 (292.3-298.7) | 1 | 61.9 (60.3-63.6) | 1 | 332.8 (329.4-336.2) | 1 |
| Yes | 460.6 (456.0-465.3) | 1.49 (1.47-1.51) | 23.9 (23.0-24.8) | 2.46 (2.35-2.57) | 370.4 (366.3-374.5) | 1.22 (1.20-1.24) |
| Opioids‖ | ||||||
| No | 288.7 (285.2-292.2) | 1 | 50.8 (49.5-52.1) | 1 | 297.0 (293.5-30.6) | 1 |
| Yes | 431.0 (427.0-435.0) | 1.49 (1.47-1.51) | 27.5 (26.5-28.6) | 1.87 (1.78-1.96) | 393.2 (389.5-397.1) | 1.28 (1.26-1.30) |
| Gabapentin starting dose (mg, fifths) | ||||||
| 1 (100-300) | 343.7 (338.4-349.1) | 1 | 38.0 (36.3-39.6) | 1 | 377.5 (371.9-383.1) | 1 |
| 2 (300.01-450) | 350.2 (343.3-357.3) | 1.02 (1.00-1.05) | 33.7 (31.6-35.8) | 0.89 (0.83-0.97) | 364.8 (357.7-372.0) | 0.98 (0.96-1.01) |
| 3 (450.01-900) | 375.9 (370.9-381.0) | 1.07 (1.05-1.10) | 42.5 (40.9-44.2) | 1.11 (1.05-1.18) | 343.6 (338.8-348.5) | 1.02 (1.00-1.04) |
| 4 (900.01-1071.4) | 423.0 (414.2-341.9) | 1.13 (1.10-1.16) | 35.3 (32.9-37.8) | 0.88 (0.81-0.96) | 320.3 (312.7-328.0) | 0.98 (0.96-1.01) |
| 5 (1071.41-4800) | 354.5 (348.9-360.1) | 1.05 (1.03-1.07) | 45.8 (43.9-47.8) | 1.23 (1.16-1.31) | 329.5 (324.2-335.0) | 1.03 (1.01-1.05) |
| Gabapentin average dose (mg, fifths) | ||||||
| 1 (100-300) | 332.8 (326.9-338.7) | 1 | 36.0 (34.2-37.9) | 1 | 376.7 (370.4-383.0) | 1 |
| 2 (300.01-600) | 343.4 (337.5-349.4) | 1.05 (1.02-1.07) | 36.9 (35.1-38.9) | 1.05 (0.97-1.13) | 375.9 (369.7-382.2) | 1.1 (0.99-1.03) |
| 3 (600.01-900) | 367.3 (361.5-373.2) | 1.09 (1.06-1.11) | 40.5 (38.7-42.5) | 1.12 (1.05-1.20) | 337.9 (332.3-343.6) | 1.1 (0.98-1.03) |
| 4 (900.01-1261.4) | 370.1 (364.4-376.0) | 1.09 (1.07-1.12) | 36.9 (35.1-38.7) | 1.02 (0.95-1.10) | 328.1 (322.7-333.6) | 1.00 (0.98-1.03) |
| 5 (1261.41-4800) | 409.9 (406.4-416.5) | 1.19 (1.16-1.21) | 50.8 (48.6-53.0) | 1.37 (1.28-1.46) | 330.5 (324.7-336.4) | 1.08 (1.05-1.11) |
| Gabapentin maximum dose (mg, fifths) | ||||||
| 1 (100-303.1) | 334.7 (328.8-340.7) | 1 | 36.0 (34.2-38.0) | 1 | 370.7 (364.4-377.0) | 1 |
| 2 (300.11-706.4) | 337.1 (331.2-343.1) | 1.03 (1.01-1.06) | 36.4 (34.6-38.4) | 1.04 (0.96-1.12) | 371.1 (364.8-377.4) | 1.01 (0.99-1.04) |
| 3 (706.5-1047.6) | 371.3 (365.3-377.4) | 1.09 (1.06-1.12) | 40.4 (38.6-42.4) | 1.12 (1.04-1.20) | 335.0 (329.3-340.8) | 1.01 (0.99-1.04) |
| 4 (1047.7-1542.9) | 360.8 (355.0-366.8) | 1.07 (1.04-1.10) | 37.1 (35.3-39.0) | 1.03 (0.96-1.11) | 329.9 (324.3-335.6) | 1.01 (0.99-1.04) |
| 5 (1542.91-4800) | 412.4 (406.3-418.6) | 1.20 (1.17-1.23) | 49.5 (47.5-51.5) | 1.35 (1.26-1.44) | 342.1 (336.6-347.7) | 1.10 (1.07-1.12) |
*
Adjusted for age, sex, IMD, history of overdose.
§
Not adjusted for history of overdose.
†
Missing for n = 33,480, 6.96%.
‡
Missing for n = 7,101, 1.48%.
‖
Drug use is concurrent with gabapentin.
IMD, Indices of Multiple Deprivation.