Carbamazepine versus phenytoin monotherapy for epilepsy: an individual participant data review

BACKGROUND

This is an updated version of the original Cochrane Review published in Issue 2, 2002 and its subsequent updates in 2010 and 2015.Epilepsy is a common neurological condition in which recurrent, unprovoked seizures are caused by abnormal electrical discharges from the brain. It is believed that with effective drug treatment, up to 70% of individuals with active epilepsy have the potential to become seizure-free and go into long-term remission shortly after starting drug therapy with a single antiepileptic drug in monotherapy.Worldwide, carbamazepine and phenytoin are commonly-used broad spectrum antiepileptic drugs, suitable for most epileptic seizure types. Carbamazepine is a current first-line treatment for partial onset seizures in the USA and Europe. Phenytoin is no longer considered a first-line treatment due to concerns over adverse events associated with its use, but the drug is still commonly used in low- to middle-income countries because of its low cost. No consistent differences in efficacy have been found between carbamazepine and phenytoin in individual trials, although the confidence intervals generated by these studies are wide. Differences in efficacy may therefore be shown by synthesising the data of the individual trials.

OBJECTIVES

To review the time to withdrawal, six- and 12-month remission, and first seizure with carbamazepine compared to phenytoin, used as monotherapy in people with partial onset seizures (simple partial, complex partial, or secondarily generalised tonic-clonic seizures), or generalised tonic-clonic seizures, with or without other generalised seizure types.

SEARCH METHODS

For the latest update we searched the Cochrane Epilepsy Group's Specialised Register (1st November 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO, 1st November 2016), MEDLINE (Ovid, 1946 to 1 November 2016), ClinicalTrials.gov (1 November 2016), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP, 1st November 2016). Previously we also searched SCOPUS (1823 to 16th September 2014) as an alternative to Embase, but this is no longer necessary, because randomised and quasi-randomised controlled trials in Embase are now included in CENTRAL. We handsearched relevant journals, contacted pharmaceutical companies, original trial investigators and experts in the field.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in children or adults with partial onset seizures or generalised onset tonic-clonic seizures, comparing carbamazepine monotherapy versus phenytoin monotherapy.

DATA COLLECTION AND ANALYSIS

This is an individual participant data (IPD) review. Our primary outcome was time to withdrawal of allocated treatment, and our secondary outcomes were time to six-month remission, time to 12-month remission, and time to first seizure post-randomisation. We used Cox proportional hazards regression models to obtain study-specific estimates of hazard ratios (HRs) with 95% confidence intervals (CIs) and the generic inverse variance method to obtain the overall pooled HR and 95% CI.

MAIN RESULTS

IPD were available for 595 participants out of 1192 eligible individuals, from four out of 12 trials (i.e. 50% of the potential data). For remission outcomes, HR greater than 1 indicates an advantage for phenytoin; and for first seizure and withdrawal outcomes, HR greater than 1 indicates an advantage for carbamazepine. The methodological quality of the four studies providing IPD was generally good and we rated it at low risk of bias overall in the analyses.The main overall results (pooled HR adjusted for seizure type) were time to withdrawal of allocated treatment: 1.04 (95% CI 0.78 to 1.39; three trials, 546 participants); time to 12-month remission: 1.01 (95% CI 0.78 to 1.31; three trials, 551 participants); time to six-month remission: 1.11 (95% CI 0.89 to 1.37; three trials, 551 participants); and time to first seizure: 0.85 (95% CI 0.70 to 1.04; four trials, 582 participants). The results suggest no overall statistically significant difference between the drugs for these outcomes. There is some evidence of an advantage for phenytoin for individuals with generalised onset seizures for our primary outcome (time to withdrawal of allocated treatment): pooled HR 0.42 (95% CI 0.18 to 0.96; two trials, 118 participants); and a statistical interaction between treatment effect and epilepsy type (partial versus generalised) for this outcome (P = 0.02). However, misclassification of seizure type for up to 48 individuals (32% of those with generalised epilepsy) may have confounded the results of this review. Despite concerns over side effects leading to the withdrawal of phenytoin as a first-line treatment in the USA and Europe, we found no evidence that phenytoin is more likely to be associated with serious side effects than carbamazepine; 26 individuals withdrew from 290 randomised (9%) to carbamazepine due to adverse effects, compared to 12 out of 299 (4%) randomised to phenytoin from four studies conducted in the USA and Europe (risk ratio (RR) 1.42, 95% CI 1.13 to 1.80, P = 0.014). We rated the quality of the evidence as low to moderate according to GRADE criteria, due to imprecision and potential misclassification of seizure type.

AUTHORS' CONCLUSIONS

We have not found evidence for a statistically significant difference between carbamazepine and phenytoin for the efficacy outcomes examined in this review, but CIs are wide and we cannot exclude the possibility of important differences. There is no evidence in this review that phenytoin is more strongly associated with serious adverse events than carbamazepine. There is some evidence that people with generalised seizures may be less likely to withdraw early from phenytoin than from carbamazepine, but misclassification of seizure type may have impacted upon our results. We recommend caution when interpreting the results of this review, and do not recommend that our results alone should be used in choosing between carbamazepine and phenytoin. We recommend that future trials should be designed to the highest quality possible, with considerations of allocation concealment and masking, choice of population, choice of outcomes and analysis, and presentation of results.

Carbamazepine versus phenobarbitone monotherapy for epilepsy: an individual participant data review

BACKGROUND

This is an updated version of the original Cochrane Review, first published in Issue 1, 2003 and updated in 2015. This review is one in a series of Cochrane Reviews investigating pair-wise monotherapy comparisons.Epilepsy is a common neurological condition in which abnormal electrical discharges from the brain cause recurrent unprovoked seizures. It is believed that with effective drug treatment, up to 70% of individuals with active epilepsy have the potential to become seizure-free and go into long-term remission shortly after starting drug therapy with a single antiepileptic drug in monotherapy.Worldwide, carbamazepine and phenobarbitone are commonly used broad-spectrum antiepileptic drugs, suitable for most epileptic seizure types. Carbamazepine is a current first-line treatment for partial onset seizures, and is used in the USA and Europe. Phenobarbitone is no longer considered a first-line treatment because of concerns over associated adverse events, particularly documented behavioural adverse events in children treated with the drug. However, phenobarbitone is still commonly used in low- and middle-income countries because of its low cost. No consistent differences in efficacy have been found between carbamazepine and phenobarbitone in individual trials; however, the confidence intervals generated by these studies are wide, and therefore, synthesising the data of the individual trials may show differences in efficacy.

OBJECTIVES

To review the time to withdrawal, remission, and first seizure of carbamazepine compared with phenobarbitone when used as monotherapy in people with partial onset seizures (simple or complex partial and secondarily generalised) or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

SEARCH METHODS

For the latest update, we searched the following databases on 18 August 2016: the Cochrane Epilepsy Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO), MEDLINE (Ovid, from 1946), the US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov), and the World Health Organization International Clinical Trials Registry Platform (ICTRP). Previously we also searched SCOPUS (from 1823) as an alternative to Embase, but this is no longer necessary, because randomised controlled trials (RCTs) and quasi-RCTs in Embase are now included in CENTRAL. We handsearched relevant journals and contacted pharmaceutical companies, original trial investigators, and experts in the field.

SELECTION CRITERIA

RCTs in children or adults with partial onset seizures or generalised onset tonic-clonic seizures with a comparison of carbamazepine monotherapy versus phenobarbitone monotherapy.

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review. Our primary outcome was 'time to withdrawal of allocated treatment', and our secondary outcomes were 'time to achieve 12-month remission', 'time to achieve six-month remission', 'time to first seizure post-randomisation', and 'adverse events'. We used Cox proportional hazards regression models to obtain study-specific estimates of hazard ratios (HRs) with 95% confidence intervals (CIs), with the generic inverse variance method used to obtain the overall pooled HR and 95% CI.

MAIN RESULTS

IPD were available for 836 participants out of 1455 eligible individuals from six out of 13 trials; 57% of the potential data. For remission outcomes, HR > 1 indicated an advantage for phenobarbitone, and for first seizure and withdrawal outcomes, HR > 1 indicated an advantage for carbamazepine.The main overall results (pooled HR adjusted for seizure type, 95% CI) were HR 1.50 for time to withdrawal of allocated treatment (95% CI 1.15 to 1.95; P = 0.003); HR 0.93 for time to achieve 12-month remission (95% CI 0.72 to 1.20; P = 0.57); HR 0.99 for time to achieve six-month remission (95% CI 0.80 to 1.23; P = 0.95); and HR 0.87 for time to first seizure (95% CI 0.72 to 1.06; P = 0.18). Results suggest an advantage for carbamazepine over phenobarbitone in terms of time to treatment withdrawal and no statistically significant evidence between the drugs for the other outcomes. We found evidence of a statistically significant interaction between treatment effect and seizure type for time to first seizure recurrence (Chi² test for subgroup differences P = 0.03), where phenobarbitone was favoured for partial onset seizures (HR 0.76, 95% CI 0.60 to 0.96; P = 0.02) and carbamazepine was favoured for generalised onset seizures (HR 1.23, 95% CI 0.88 to 1.77; P = 0.27). We found no evidence of an interaction between treatment effect and seizure type for the other outcomes. However, methodological quality of the included studies was variable, with 10 out of the 13 included studies (4 out of 6 studies contributing IPD) judged at high risk of bias for at least one methodological aspect, leading to variable individual study results, and therefore, heterogeneity in the analyses of this review. We conducted sensitivity analyses to examine the impact of poor methodological aspects, where possible.

AUTHORS' CONCLUSIONS

Overall, we found evidence suggestive of an advantage for carbamazepine in terms of drug effectiveness compared with phenobarbitone (retention of the drug in terms of seizure control and adverse events) and evidence suggestive of an association between treatment effect and seizure type for time to first seizure recurrence (phenobarbitone favoured for partial seizures and carbamazepine favoured for generalised seizures). However, this evidence was judged to be of low quality due to poor methodological quality and the potential impact on individual study results (and therefore variability (heterogeneity) present in the analysis within this review), we encourage caution when interpreting the results of this review and do not advocate that the results of this review alone should be used in choosing between carbamazepine and phenobarbitone. We recommend that future trials should be designed to the highest quality possible with considerations for allocation concealment and masking, choice of population, choice of outcomes and analysis, and presentation of results.

Topiramate versus carbamazepine monotherapy for epilepsy: an individual participant data review

BACKGROUND

Epilepsy is a common neurological condition in which abnormal electrical discharges from the brain cause recurrent unprovoked seizures. It is believed that with effective drug treatment, up to 70% of individuals with active epilepsy have the potential to become seizure-free and go into long-term remission shortly after starting drug therapy, the majority of which may be able to achieve remission with a single antiepileptic drug (AED).The correct choice of first-line antiepileptic therapy for individuals with newly diagnosed seizures is of great importance. It is important that the choice of AED for an individual is based on the highest-quality evidence available regarding the potential benefits and harms of various treatments. It is also important to compare the efficacy and tolerability of AEDs appropriate to given seizure types.Topiramate and carbamazepine are commonly used AEDs. Performing a synthesis of the evidence from existing trials will increase the precision of results of outcomes relating to efficacy and tolerability, and may help inform a choice between the two drugs.

OBJECTIVES

To assess the effects of topiramate monotherapy versus carbamazepine monotherapy for epilepsy in people with partial-onset seizures (simple or complex partial and secondarily generalised) or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (14 April 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) (14 April 2016) and MEDLINE (Ovid, 1946 to 14 April 2016). We imposed no language restrictions. We also contacted pharmaceutical companies and trial investigators.

SELECTION CRITERIA

Randomised controlled trials in children or adults with partial-onset seizures or generalised-onset tonic-clonic seizures with or without other generalised seizure types with a comparison of monotherapy with either topiramate or carbamazepine.

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review. Our primary outcome was 'time to withdrawal of allocated treatment', and our secondary outcomes were 'time to first seizure post randomisation', 'time to 6-month remission, 'time to 12-month remission' and incidence of adverse events. We used Cox proportional hazards regression models to obtain trial-specific estimates of hazard ratios (HRs) with 95% confidence intervals (CIs), and used the generic inverse variance method to obtain the overall pooled HRs and 95% CIs.

MAIN RESULTS

IPD were available for 1151 of 1239 eligible individuals from two of three eligible studies (93% of the potential data). A small proportion of individuals recruited into these trials had 'unclassified seizures;' for analysis purposes, these individuals are grouped with those with generalised onset seizures. For remission outcomes, a HR < 1 indicated an advantage for carbamazepine, and for first seizure and withdrawal outcomes, a HR < 1 indicated an advantage for topiramate.The main overall results, given as pooled HR adjusted for seizure type (95% CI) were: for time to withdrawal of allocated treatment 1.16 (0.98 to 1.38); time to first seizure 1.11 (0.96 to 1.29); and time to 6-month remission 0.88 (0.76 to 1.01). There were no statistically significant differences between the drugs. A statistically significant advantage for carbamazepine was shown for time to 12-month remission: 0.84 (0.71 to 1.00).The results of this review are applicable mainly to individuals with partial-onset seizures; 85% of included individuals experienced seizures of this type at baseline. For individuals with partial-onset seizures, a statistically significant advantage for carbamazepine was shown for time to withdrawal of allocated treatment (HR 1.20, 95% CI 1.00 to 1.45) and time to 12-month remission (HR 0.84, 95% CI 0.71 to 1.00). No statistically significant differences were apparent between the drugs for other outcomes and for the limited number of individuals with generalised-onset tonic-clonic seizures with or without other generalised seizure types or unclassified seizures.The most commonly reported adverse events with both drugs were drowsiness or fatigue, 'pins and needles' (tingling sensation), headache, gastrointestinal disturbance and anxiety or depression The rate of adverse events was similar across the two drugs.We judged the methodological quality of the included trials generally to be good; however, there was some evidence that the open-label design of the larger of the two trials may have influenced the withdrawal rate from the trial. Hence, we judged the evidence for the primary outcome of treatment withdrawal to be moderate for individuals with partial-onset seizures and low for individuals with generalised-onset seizures. For efficacy outcomes (first seizure, remission), we judged the evidence from this review to be high for individuals with partial-onset seizures and moderate for individuals with generalised-onset or unclassified seizures.

AUTHORS' CONCLUSIONS

For individuals with partial-onset seizures, there is evidence that carbamazepine is less likely to be withdrawn and that 12-month remission will be achieved earlier than with topiramate. No differences were found between the drugs in terms of the outcomes measured in the review for individuals with generalised tonic-clonic seizures with or without other seizure types or unclassified epilepsy; however, we encourage caution in the interpretation of these results due to the small numbers of participants with these seizure types.We recommend that future trials should be designed to the highest quality possible and take into consideration masking, choice of population, classification of seizure type, duration of follow-up, choice of outcomes and analysis, and presentation of results.

Lamotrigine versus carbamazepine monotherapy for epilepsy: an individual participant data review

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 1, 2006 of the Cochrane Database of Systematic Reviews.Epilepsy is a common neurological condition in which abnormal electrical discharges from the brain cause recurrent unprovoked seizures. It is believed that with effective drug treatment up to 70% of individuals with active epilepsy have the potential to become seizure-free and to go into long-term remission shortly after starting drug therapy with a single antiepileptic drug (AED) in monotherapy.The correct choice of first-line antiepileptic therapy for individuals with newly diagnosed seizures is of great importance. It is important that the choice of AEDs for an individual is made using the highest quality evidence regarding the potential benefits and harms of the various treatments. It is also important that the effectiveness and tolerability of AEDs appropriate to given seizure types are compared to one another.Carbamazepine or lamotrigine are first-line recommended treatments for new onset partial seizures and as a first- or second-line treatment for generalised tonic-clonic seizures. Performing a synthesis of the evidence from existing trials will increase the precision of the results for outcomes relating to efficacy and tolerability and may assist in informing a choice between the two drugs.

OBJECTIVES

To review the time to withdrawal, remission and first seizure with lamotrigine compared to carbamazepine when used as monotherapy in people with partial onset seizures (simple or complex partial and secondarily generalised) or generalised onset tonic-clonic seizures (with or without other generalised seizure types).

SEARCH METHODS

The first searches for this review were run in 1997. For the most recent update we searched the Cochrane Epilepsy Group Specialized Register (17 October 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO, 17 October 2016) and MEDLINE (Ovid, 1946 to 17 October 2016). We imposed no language restrictions. We also contacted pharmaceutical companies and trial investigators.

SELECTION CRITERIA

Randomised controlled trials in children or adults with partial onset seizures or generalised onset tonic-clonic seizures comparing monotherapy with either carbamazepine or lamotrigine.

DATA COLLECTION AND ANALYSIS

This was an individual participant data (IPD) review. Our primary outcome was time to withdrawal of allocated treatment and our secondary outcomes were time to first seizure post-randomisation, time to six-month, 12-month and 24-month remission, and incidence of adverse events. We used Cox proportional hazards regression models to obtain trial-specific estimates of hazard ratios (HRs) with 95% confidence intervals (CIs), using the generic inverse variance method to obtain the overall pooled HR and 95% CI.

MAIN RESULTS

We included 13 studies in this review. Individual participant data were available for 2572 participants out of 3394 eligible individuals from nine out of 13 trials: 78% of the potential data. For remission outcomes, a HR < 1 indicated an advantage for carbamazepine and for first seizure and withdrawal outcomes a HR < 1 indicated an advantage for lamotrigine.The main overall results (pooled HR adjusted for seizure type) were: time to withdrawal of allocated treatment (HR 0.72, 95% CI 0.63 to 0.82), time to first seizure (HR 1.22, 95% CI 1.09 to 1.37) and time to six-month remission (HR 0.84, 95% CI 0.74 to 0.94), showing a significant advantage for lamotrigine compared to carbamazepine for withdrawal but a significant advantage for carbamazepine compared to lamotrigine for first seizure and six-month remission. We found no difference between the drugs for time to 12-month remission (HR 0.91, 95% CI 0.77 to 1.07) or time to 24-month remission (HR 1.00, 95% CI 0.80 to 1.25), however only two trials followed up participants for more than one year so the evidence is limited.The results of this review are applicable mainly to individuals with partial onset seizures; 88% of included individuals experienced seizures of this type at baseline. Up to 50% of the limited number of individuals classified as experiencing generalised onset seizures at baseline may have had their seizure type misclassified, therefore we recommend caution when interpreting the results of this review for individuals with generalised onset seizures.The most commonly reported adverse events for both of the drugs across all of the included trials were dizziness, fatigue, gastrointestinal disturbances, headache and skin problems. The rate of adverse events was similar across the two drugs.The methodological quality of the included trials was generally good, however there is some evidence that the design choice of masked or open-label treatment may have influenced the withdrawal rates of the trials. Hence, we judged the quality of the evidence for the primary outcome of treatment withdrawal to be moderate for individuals with partial onset seizures and low for individuals with generalised onset seizures. For efficacy outcomes (first seizure, remission), we judged the quality of evidence to be high for individuals with partial onset seizures and moderate for individuals with generalised onset seizures.

AUTHORS' CONCLUSIONS

Lamotrigine was significantly less likely to be withdrawn than carbamazepine but the results for time to first seizure suggested that carbamazepine may be superior in terms of seizure control. A choice between these first-line treatments must be made with careful consideration. We recommend that future trials should be designed to the highest quality possible with consideration of masking, choice of population, classification of seizure type, duration of follow-up, choice of outcomes and analysis, and presentation of results.

Anticonvulsants for tinnitus

BACKGROUND

Tinnitus is the perception of sound or noise in the absence of an external or internal acoustic stimulation. It is a common and potentially distressing symptom for which no adequate therapy exists.

OBJECTIVES

To assess the effectiveness of anticonvulsants in patients with chronic tinnitus.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, CENTRAL (2010, Issue 2), MEDLINE, EMBASE, bibliographies and additional sources for published and unpublished trials. The date of the most recent search was 26 May 2010.

SELECTION CRITERIA

We selected randomised controlled trials in patients with chronic tinnitus comparing orally administered anticonvulsants with placebo. The primary outcome was improvement in tinnitus measured with validated questionnaires. Secondary outcomes were improvement in tinnitus measured with self-assessment scores, improvement in global well-being or accompanying symptoms, and adverse drug effects.

DATA COLLECTION AND ANALYSIS

Three authors assessed risk of bias and extracted data independently.

MAIN RESULTS

Seven trials (453 patients) were included in this review. These studies investigated four different anticonvulsants: gabapentin, carbamazepine, lamotrigine and flunarizine. The risk of bias of most studies was 'high' or 'unclear'. Three studies included a validated questionnaire (primary outcome). None of them showed a significant positive effect of anticonvulsants. One study showed a significant negative effect of gabapentin compared to placebo with an increase in Tinnitus Questionnaire (TQ) score of 18.4 points (standardised mean difference (SMD) 0.82, 95% confidence interval (CI) 0.07 to 1.58). A second study showed a positive, non-significant effect of gabapentin with a difference compared to placebo of 2.4 points on the Tinnitus Handicap Inventory (THI) (SMD -0.11, 95% CI -0.48 to 0.25). When the data from these two studies are pooled no effect of gabapentin is found (SMD 0.07, 95% CI -0.26 to 0.40). A third study reported no differences on the THI after treatment with gabapentin compared to placebo (exact numbers could not be extracted from the article).A meta-analysis of 'any positive effect' (yes versus no) based on a self-assessment score (secondary outcome) showed a small favourable effect of anticonvulsants (RD 14%, 95% CI 6% to 22%). A meta-analysis of 'near or total eradication of tinnitus annoyance' showed no effect of anticonvulsants (risk difference (RD) 4%, 95% CI -2% to 11%). Side effects of the anticonvulsants used were experienced by 18% of patients.

AUTHORS' CONCLUSIONS

Current evidence regarding the effectiveness of anticonvulsants in patients with tinnitus has significant risk of bias. There is no evidence from studies performed so far to show that anticonvulsants have a large positive effect in the treatment of tinnitus but a small effect (of doubtful clinical significance) has been demonstrated.