Worsening of myasthenia due to antiepileptic, antipsychotic, antidepressant, and sedative medication: An estimation of risk based on reporting frequency

Treatment of Depression in Adolescents With Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disorder in which, most commonly, there is a production of autoantibodies against the nicotinic acetylcholinergic receptors at the neuromuscular junction, resulting in skeletal muscle weakness. For pediatric patients, literature addressing the psychiatric implications of MG and suitable treatment options for individuals with concurrent psychiatric illnesses is scarce. In this case report, an adolescent with MG and comorbid depression was treated following a suicide attempt via self-poisoning. The patient experienced an improvement of depressive symptoms upon initiating fluoxetine, despite concerns raised by previous studies suggesting that fluoxetine might block acetylcholine receptors at the neuromuscular junction with varying degrees of affinity, potentially worsening MG symptoms. In this case, our patient exhibited sustained control of her MG symptoms without exacerbation once she was started on fluoxetine. This case highlights the value of further investigation into the safety and efficacy of selective serotonin reuptake inhibitors (SSRIs) in the management of depression among pediatric patients with MG.

Sensitivity and specificity in signal detection with the reporting odds ratio and the information component

PURPOSE

As measures of association between an adverse drug reaction (ADR) and exposure to a drug the reporting odds ratio (ROR) and the information component (IC) can be used. We sought to test the reliability of signal detection with these.

METHODS

We simulated ADR counts as binomially distributed random numbers for different expected ADR frequencies and theoretical reporting odds ratios (RORs). We then calculated the empirical IC and the empirical ROR and their confidence intervals. The rate of signals that was detected despite a theoretical ROR of 1 represented the false positive rate, and represented the sensitivity if the ROR was >1.

RESULTS

For expected case counts below 1 the false positive rate oscillates from 0.01 to 0.1 even though 0.025 were intended. Even beyond expected case counts of 5 oscillations can cover a range of 0.018 to 0.035. The first n oscillations with the largest amplitude are eliminated if a minimum case count of n is required. To detect an ROR of 2 with a sensitivity of 0.8, a minimum of 12 expected ADRs are required. In contrast, 2 expected ADRs suffice to detect an ROR of 4.

CONCLUSION

Summaries of measures for disproportionality should include the expected number of cases in the group of interest if a signal was detected. If no signal was detected the sensitivity for the detection of a representative ROR or the minimum ROR that could be detected with probability 0.8 should be reported.

The risk of worsening of myasthenia by cardiovascular medication as reflected by reporting frequency

BACKGROUND AND PURPOSE

Some groups of cardiovascular drugs (beta-blocking drugs, Ca antagonists, antiarrhythmics) are listed as potentially worsening myasthenia. An empirical basis for alternative recommendations for antihypertensive and antiarrhythmic therapy in myasthenia patients has not yet been provided.

METHODS

From the World Health Organization pharmacovigilance database, we retrieved total and myasthenia-related counts of adverse drug reactions for various groups of drugs used in cardiovascular disease and drugs with related mechanism of action used in other indications. We calculated the reporting odds ratio as a measure of a disproportional fraction of myasthenia-related events among all events. A 95% confidence interval of reporting odds ratio (ROR) >1 was taken as an indication for a higher risk. Because our approach involves a considerable number of tests, this situation is referred to as a signal that requires additional confirmation.

RESULTS

A signal for an increased risk was noted for tizanidine, for alpha-blocking drugs, for beta-blocking drugs, and for Ca antagonists. ROR indicated a lower-than-average risk for salbutamol, angiotensin receptor antagonists, oral anticoagulants, thrombocytic function inhibitors, and heparins.

CONCLUSIONS

Angiotensin receptor antagonists, angiotensin-converting enzyme inhibitors, and diuretics seem to be safe in antihypertensive therapy. Surprisingly, and yet requiring confirmation by case reports, alpha receptor-blocking drugs seem to carry a risk of myasthenia worsening. Amiodarone seems to be a safe alternative in antiarrhythmic therapy in patients with myasthenia.