Antiepileptic Drugs Associated with Stevens-Johnson Syndrome
The aromatic antiepileptic drugs—carbamazepine, phenytoin, lamotrigine, and phenobarbital—are the primary culprits for Stevens-Johnson syndrome, with carbamazepine, phenytoin, and lamotrigine carrying the highest absolute risk. 1, 2
High-Risk Antiepileptic Drugs
Classic Aromatic AEDs (Highest Risk)
The following drugs demonstrate the strongest association with SJS/TEN:
- Phenytoin: Absolute risk of 45.86 cases per 100,000 new users 2
- Lamotrigine: Absolute risk of 44.17 cases per 100,000 new users 2
- Carbamazepine: Absolute risk of 20.38 cases per 100,000 new users 2
- Phenobarbital: Established association with SJS/TEN 1, 3
These aromatic antiepileptics share a common structural feature (aromatic ring) and likely act through similar pathogenic mechanisms 4. The risk is highest within the first 63 days of treatment, with most cases occurring in the first month 1, 5.
Newer Generation AEDs
Among drugs approved after 1990, three have emerged as causes:
- Lamotrigine (especially when used concomitantly with valproic acid) 6
- Oxcarbazepine: Shows strong association (OR: 80.7) 4, 7
- Zonisamide: Significant association demonstrated 6, 8
Lamotrigine deserves special mention as it appears more commonly in younger women, while phenytoin-associated cases occur more often in older men 3.
Lower Risk or Uncertain Association
Several widely-used AEDs show no confirmed causal association despite increased reporting:
- Valproate: Despite increased odds ratios in some studies, the ALDEN causality algorithm suggests no true causal association 2
- Gabapentin: No ALDEN-confirmed cases among 116,037 new users 2
- Pregabalin: No ALDEN-confirmed cases among 59,967 new users 2
- Levetiracetam: No observed cases among 96,777 new users 2
- Topiramate: No observed cases among 11,307 new users 2
- Clonazepam: No observed cases among 18,075 new users 2
Critical Clinical Considerations
Genetic Susceptibility
HLA-B*1502 screening is essential before prescribing aromatic antiepileptics in patients of Southeast Asian descent (particularly Han Chinese, Thai, Malaysian populations) 4, 8. This allele shows strong associations with:
- Carbamazepine-induced SJS/TEN
- Phenytoin-induced SJS/TEN (30.8% of cases)
- Oxcarbazepine-induced SJS/TEN (100% in one study)
- Lamotrigine-induced SJS/TEN (33% of cases)
Other HLA associations include HLA-A02:07, HLA-B46:01, and HLA-DRB1*08:03 with zonisamide 8.
Common Pitfalls
Avoid falsely implicating acetaminophen or ibuprofen: These drugs are often started to treat prodromal fever and mucosal symptoms of SJS/TEN before the diagnosis becomes apparent (protopathic effect) 1. However, both can rarely cause true SJS, so clinical judgment is required 6.
Immediate Action Required
Any suspected causative medication must be withdrawn immediately as this decreases mortality risk 1. The latency period typically does not exceed the first month of treatment, and over 90% of cases occur within the first 63 days 5.
Pediatric Considerations
In children, antiepileptic drugs are the most common medication class causing SJS/TEN, closely followed by antibiotics 1, 6. Trimethoprim-sulfamethoxazole, phenytoin, and lamotrigine (when used with valproic acid) are the most frequently implicated specific agents 6.