Abstract
This pharmacoepidemiology study uses Scandinavian birth registry data to estimate the association between modafinil use during early pregnancy and major congenital malformations among infants born in Norway and Sweden between 2005-2006 and 2016-2017.
Modafinil is used to improve wakefulness in adults with excessive sleepiness due to narcolepsy, for fatigue related to multiple sclerosis, and for the treatment of attention-deficit/hyperactivity disorder. In 2018, an interim report from a manufacturer-established pregnancy registry reported a prevalence of 15% for major malformation in infants exposed to modafinil during pregnancy, spurring regulatory bodies to amend product information.1,2,3 Recently, a Danish study reported a major malformation rate of 12% (n = 6) among 49 infants exposed to modafinil during early pregnancy compared with 3.9% (n = 32 466) among 828 644 unexposed to modafinil (adjusted odd ratio, 2.7; 95% CI, 1.1-6.9).4 To add to the emerging evidence, we investigated if modafinil use during early pregnancy was associated with major malformations in Norway and Sweden.
Methods
All singleton pregnancies resulting in live births in the nationwide medical birth registers in Norway (2005-2017) and Sweden (2006-2016) were identified and linked to their respective prescribed drug registers (containing data on medication dispensed at pharmacies) and national patient registers (containing data on diagnoses made during hospital-based specialist care). We excluded pregnancies with missing gestational age and those resulting in infants born with chromosomal anomalies (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision [ICD-10] codes Q90-Q99).
Exposure to modafinil (Anatomical Therapeutic Chemical code N06BA07) during the first trimester was defined as 1 or more filled prescriptions within the 30 days before the date of last menstrual period and the end of the first trimester (day 97 of gestation). A secondary exposure definition was 1 or more filled prescriptions during the first trimester. Unexposed pregnant women had no filled prescriptions of modafinil during the year before the last menstrual period to the end of the first trimester.
Characteristics of women, including maternal age at delivery, prepregnancy body mass index, and smoking during early pregnancy, were reported along with diagnoses recorded during the year before the last menstrual period to the end of the first trimester, and filled prescriptions during the 90 days before the last menstrual period to the end of the first trimester.
Major malformations were identified by ICD-10 codes.5 The number and percentage of cases of malformations after exposure or without exposure to modafinil was reported. Crude risk ratios and 2-sided Wald 95% CIs were calculated using SAS version 9.4 (SAS Institute Inc). This study was approved by research ethics committees in Norway and Sweden; register-based studies are exempt from informed consent.
Results
In a cohort of 1 917 605 pregnancies (744 311 in Norway and 1 173 294 in Sweden), 133 (0.007%; 38 in Norway and 95 in Sweden) were exposed to modafinil during early pregnancy. Compared with pregnant women who had not taken modafinil, pregnant women who had taken modafinil were more often overweight or obese and had higher rates of smoking and diagnoses of narcolepsy, multiple sclerosis, and attention-deficit/hyperactivity disorder (Table).
Table. Characteristics by Modafinil Exposure Status During Pregnancy in Norway (2005-2017) and Sweden (2006-2016).
| Characteristics | Exposed to modafinila | Unexposed to modafinilb |
|---|---|---|
| Pregnant women, No. (%) | 133 (0.007) | 1 917 472 (99.993) |
| Maternal age, mean (SD), y | 31.2 (5.0) | 30.6 (5.2) |
| BMI prior to pregnancy | ||
| Mean (SD)c | 26.4 (5.8) | 24.6 (4.7) |
| No. (%) | ||
| <25c | 52 (39.1) | 909 093 (47.4) |
| ≥25c | 59 (44.4) | 531 324 (27.7) |
| Missing | 22 (16.5) | 477 055 (24.9) |
| Smoking during early pregnancy, No. (%) | ||
| No | 104 (78.2) | 1 629 482 (85.0) |
| Yes | 23 (17.3) | 134 169 (7.0) |
| Missing | 6 (4.5) | 153 821 (8.0) |
| Maternal comorbidities, No. (%) | ||
| Multiple sclerosis (ICD-10 code G35) | 29 (21.8) | 2303 (0.1) |
| Narcolepsy (ICD-10 code G47.4) | 23 (17.3) | 97 (<0.1) |
| ADHD (ICD-10 code F90.0) | 6 (4.5) | 6605 (0.3) |
| Mental or behavioral disorderd | 31 (23.3) | 69 760 (3.6) |
| Maternal medications, No. (%) | ||
| Known teratogense | 3 (2.3) | 7923 (0.4) |
| Potential teratogensf | 11 (8.3) | 135 152 (7.0) |
| Analgesics (ATC code N02) | 30 (22.6) | 113 598 (5.9) |
| Antiepileptics (ATC code N03) | 24 (18.0) | 11 920 (0.6) |
| Psycholeptics (ATC code N05)g | 21 (15.8) | 58 729 (3.1) |
| Psychoanaleptics (ATC code N06)h | 35 (26.3) | 72 714 (3.8) |
| Multiple sclerosis treatmenti | 15 (11.3) | 804 (<0.1) |
| Infant major malformation, No. (%) | 3 (2.6) | 40 697 (2.1) |
Abbreviations: ADHD, attention-deficit/hyperactivity disorder; ATC, Anatomical Therapeutic Chemical; BMI, body mass index; ICD-10, International Statistical Classification of Diseases and Related Health Problems, Tenth Revision.
Defined as 1 or more filled modafinil prescriptions within the 30 days before the date of the last menstrual period to the end of the first trimester.
Defined as no filled modafinil prescriptions within the year prior to the date of the last menstrual period to the end of the first trimester.
Calculated as weight in kilograms divided by height in meters squared.
All ICD-10 chapter F diagnoses.
Includes retinoids, angiotensin-converting enzyme inhibitors, vitamin K antagonist, valproic acid, lithium, carbamazepine, oxcarbazepine, phenytoin, phenobarbital, and methotrexate.
Includes danazol, progestins, methimazole, propylthiouracil, corticosteroids, and fluconazole.
Includes barbiturates and benzodiazepines.
Includes antidepressants; modafinil was excluded.
Includes interferon beta, glatiramer acetate, fingolimod, dimethyl fumarate, teriflunomide, peginterferon beta-1a, natalizumab, and fampridine.
Overall, the rate of major malformations in the unexposed group was 2.1% (n = 40 697). There were 3 modafinil-exposed infants diagnosed as having a major malformation, resulting in a prevalence rate of 2.6% and a crude risk ratio of 1.06 (95% CI, 0.35-3.26). When restricted to only filled prescriptions during the first trimester, 75 pregnancies were exposed and 1 modafinil-exposed infant was diagnosed as having a major malformation (risk ratio, 0.44; 95% CI, 0.06-3.10).
Discussion
In this study, modafinil use during early pregnancy was not significantly associated with increased risk of major malformations. The combined Norwegian and Swedish study population had a similar proportion of modafinil-exposed pregnancies compared with the Danish study, allowing for more than double the number of exposed infants to be followed up. However, the 95% CIs estimated in this study overlap with those from the Danish study and allow for the possibility of a greater than 3-fold risk as previously reported.4
The limitations include that filled prescriptions were used as a proxy for medication use; any nonuse of modafinil would bias the results toward the null. Overall, the absolute number of exposed infants and malformations was low, hindering rigorous analyses accounting for potential confounding factors.
These results illustrate the need to focus on performing large and sufficiently powered studies for drug safety in pregnancy research, preferably from several countries, when exposures and outcomes are rare.6
Section Editor: Jody W. Zylke, MD, Deputy Editor.
References
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