Probable codeine phosphate-induced seizures

Tramadol and the risk of seizure: nested case-control study of US patients with employer-sponsored health benefits

OBJECTIVES

Tramadol is a widely prescribed analgesic that influences both opioid and monoamine neurotransmission. While seizures have been reported with its use, the risk in clinical practice has not been well characterised. We examined risk of seizure with tramadol relative to codeine, a comparable opioid analgesic.

DESIGN

Retrospective nested case-control study. For each case, we identified up to 10 controls matched on age, sex, US state of residence and date of cohort entry (±365 days). We calculated ORs to determine the association between seizure and exposure to tramadol, codeine (≥15 mg), both or neither, in the preceding 30 days.

SETTING

Cohort of patients, who had continuous health coverage and resided in the same state for≥3 years, identified from linked administrative health data in US MarketScan databases from 2009 to 2012.

PARTICIPANTS

We identified 96 753 patients with seizure and 888 540 matched controls.

PRIMARY AND SECONDARY OUTCOME MEASURES

In the primary analysis, we defined cases using a broad definition of seizure (based on either an outpatient physician claim for seizure disorder or a seizure-related emergency department visit or hospitalisation). In a secondary analysis, we used a more specific definition of seizure restricted to a hospital visit with a principal diagnosis of seizure.

RESULTS

In the primary analysis, we found no association between risk of seizure and exposure to tramadol compared with codeine (OR 1.03, 95% CI 0.93 to 1.15). However, in the secondary analysis (using a more specific definition of seizure), this association was statistically significant (OR 1.41, 95% CI 1.11 to 1.79).

CONCLUSIONS

Tramadol was not associated with an increased risk of seizure defined by inpatient and outpatient diagnoses. However, this finding was sensitive to the outcome definition used and requires further study.

[Case of non-convulsive status epilepticus after influenza virus B infection]

A 24-year-old woman was referred to our hospital because of impaired consciousness after influenza virus B infection. Neurological examination revealed mild disturbance of consciousness without other neurological abnormalities. Laboratory tests showed elevated serum CRP, IL-6 and TNF-α levels. The level of IL-6 in the cerebrospinal fluid was also slightly elevated. Electroencephalography (EEG) disclosed almost continuous generalized spike and wave complexes and multiple spikes and wave complexes at 1.5-3 Hz. Brain MRI was normal. She was diagnosed as having influenza encephalopathy presenting non-convulsive status epilepticus (NCSE), and commenced methylprednisolone pulse therapy followed by prednisolone with gradual tapering. She was also treated with intravenous phenytoin and oral sodium valproate for NCSE. The next day, her consciousness level had improved. Although she became alert, epileptic discharges on EEG were still observed on the seventh hospital day, and levetiracetam was added. Then, her epileptic discharges almost completely disappeared on the twelfth hospital day. She was discharged without any neurological deficit. We consider this patient to be a case of transient NCSE due to influenza encephalopathy; alternatively, she may have epileptic traits and her NCSE may have been provoked by influenza virus infection.

Intoxication with over-the-counter antitussive medication containing dihydrocodeine and chlorpheniramine causes generalized convulsion and mixed acidosis

We report a 35-year-old man who was referred to our hospital with generalized convulsion and mixed acidosis presumably caused by abuse of SS-BRON tablets, an over-the-counter (OTC) antitussive medication sold in Japan. These tablets contain dihydrocodeine phosphate, methylephedrine, chlorpheniramine, and caffeine. Although it is difficult to discern which component caused these symptoms, it seems that dihydrocodeine phosphate or methylephedrine was involved in the addiction to SS-BRON and chlorpheniramine may have caused the generalized convulsion. It should be recognized that an OTC antitussive, which is quite easy to obtain, can be abused and subsequently induce serious intoxication.