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Purpose The effect of denominator options on event rates was tested on the French part of the Study of Acute Liver Transplant (SALT). Methods SALT is a case population study of acute liver failure registered for transplantation (ALFT), exposed to non-steroidal anti-inflammatory drugs (NSAIDs) or non-overdose paracetamol, from 2005 to 2007. Population exposure was computed from the Intercontinental Medical Services' (IMS) and the French national healthcare insurance system's data as the number of defined daily doses (DDDs) sold or dispensed and the number of exposed patients. Results Nine ALFT cases were exposed to 10 NSAIDs and 49 to non-overdose paracetamol. NSAID sales ranged from 0.04 billion (niflumic acid) to 0.5 billion (ibuprofen) DDDs, amounting to 2.5 billion DDDs for all NSAIDs. The mean per-person exposure ranged from 13.1 (niflumic acid) to 43.2 (ketoprofen) DDDs, reaching 60.5 DDDs for any NSAID. The number of users ranged from 2 million (niflumic acid) to 13 million (ibuprofen), which was 26.6 million for all NSAIDs. The ALFT rates per billion DDDs ranged from 0 to 26 for individual NSAIDs and amounted to 4.6 for all NSAIDs. The ALFT rates per billion DDDs were inversely correlated with the average per-patient exposure (R2 = 0.935, p = 0.0016). The ALFT rates per million users ranged from 0.31 to 0.49, which was 0.41 for all NSAIDs, with no difference between drugs and no effect of mean per-patient exposure (R2 = 0.01, p = 0.9). Whether measured per DDD or per user, the event rate with paracetamol was three to five times higher than with NSAIDs. Conclusion ALFT risk with NSAID seems to be user dependent rather than person-time (exposure) dependent. Choosing the wrong denominator in case population studies might give erroneous results. Copyright © 2012 John Wiley & Sons, Ltd.

Purpose Fear of discontinuing concomitant anti-epileptic drugs (AEDs) may lead to potentially unnecessary and perhaps unsafe polypharmacy. The effect of withdrawing concomitant AEDs on epilepsy control was therefore studied in long-term users of levetiracetam. Methods The EULEV cohort followed patients initiating levetiracetam in France in 2005 or 2006 for one year. In those maintaining levetiracetam throughout the study period, the association of a reduction in the number of concomitant AEDs during the first six months with seizure-freedom during the last six months of follow-up was investigated using logistic regression. Results Of the 356 patients continuing levetiracetam for at least 1 year, 140 (39.3%) were seizure-free during the last six months of follow-up. Partial symptomatic or generalised idiopathic epilepsy were associated with greater seizure-freedom than partial cryptogenic disease. Factors associated with seizures were: longer disease duration, initial incapacity, increased number of seizures in the six months preceding levetiracetam initiation, and number of consultations for epilepsy in the six months preceding levetiracetam initiation. There was a trend for the association between the early reduction in the number of concomitant AEDs and seizure-free status later during follow-up, which however did not reach statistical significance in the final propensity score-adjusted multivariate model (OR = 1.8, 95%CI [0.8;4.0]). Conclusions Taking into account the various risk factors for seizures, the early reduction of concomitant AEDs was not associated with worse seizure rates during follow-up in real-life users of levetiracetam. Copyright © 2012 John Wiley & Sons, Ltd.

The effect of denominator options on event rates was tested on the French part of the Study of Acute Liver Transplant (SALT).SALT is a case population study of acute liver failure registered for transplantation (ALFT), exposed to non-steroidal anti-inflammatory drugs (NSAIDs) or non-overdose paracetamol, from 2005 to 2007. Population exposure was computed from the Intercontinental Medical Services' (IMS) and the French national healthcare insurance system's data as the number of defined daily doses (DDDs) sold or dispensed and the number of exposed patients.Nine ALFT cases were exposed to 10 NSAIDs and 49 to non-overdose paracetamol. NSAID sales ranged from 0.04 billion (niflumic acid) to 0.5 billion (ibuprofen) DDDs, amounting to 2.5 billion DDDs for all NSAIDs. The mean per-person exposure ranged from 13.1 (niflumic acid) to 43.2 (ketoprofen) DDDs, reaching 60.5 DDDs for any NSAID. The number of users ranged from 2 million (niflumic acid) to 13 million (ibuprofen), which was 26.6 million for all NSAIDs. The ALFT rates per billion DDDs ranged from 0 to 26 for individual NSAIDs and amounted to 4.6 for all NSAIDs. The ALFT rates per billion DDDs were inversely correlated with the average per-patient exposure (R(2) = 0.935, p = 0.0016). The ALFT rates per million users ranged from 0.31 to 0.49, which was 0.41 for all NSAIDs, with no difference between drugs and no effect of mean per-patient exposure (R(2) = 0.01, p = 0.9). Whether measured per DDD or per user, the event rate with paracetamol was three to five times higher than with NSAIDs.ALFT risk with NSAID seems to be user dependent rather than person-time (exposure) dependent. Choosing the wrong denominator in case population studies might give erroneous results.

Fear of discontinuing concomitant anti-epileptic drugs (AEDs) may lead to potentially unnecessary and perhaps unsafe polypharmacy. The effect of withdrawing concomitant AEDs on epilepsy control was therefore studied in long-term users of levetiracetam.The EULEV cohort followed patients initiating levetiracetam in France in 2005 or 2006 for one year. In those maintaining levetiracetam throughout the study period, the association of a reduction in the number of concomitant AEDs during the first six months with seizure-freedom during the last six months of follow-up was investigated using logistic regression.Of the 356 patients continuing levetiracetam for at least 1 year, 140 (39.3%) were seizure-free during the last six months of follow-up. Partial symptomatic or generalised idiopathic epilepsy were associated with greater seizure-freedom than partial cryptogenic disease. Factors associated with seizures were: longer disease duration, initial incapacity, increased number of seizures in the six months preceding levetiracetam initiation, and number of consultations for epilepsy in the six months preceding levetiracetam initiation. There was a trend for the association between the early reduction in the number of concomitant AEDs and seizure-free status later during follow-up, which however did not reach statistical significance in the final propensity score-adjusted multivariate model (OR = 1.8, 95%CI [0.8;4.0]).Taking into account the various risk factors for seizures, the early reduction of concomitant AEDs was not associated with worse seizure rates during follow-up in real-life users of levetiracetam.