Key messages
• Giving phenobarbital (a medicine used to control seizures) to babies born too early may have little to no effect in preventing intraventricular haemorrhage (bleeding to the brain) and death.
• The evidence is very uncertain about the effect of phenobarbital on preventing ventricular dilation (enlarged spaces in the brain) and long-term brain development.
What is bleeding to the brain (intraventricular haemorrhage)?
Large bleeds in the centre of the brain can cause disability or death in babies born too early. Unstable blood pressure and blood flow to the brain are believed to cause bleeding into the fluid-filled cavities of the brain (ventricles).
What did we want to find out?
Phenobarbital is believed to stabilise blood pressure and therefore potentially help prevent bleeding to the brain. We wanted to find out whether phenobarbital was better than no medicine or a placebo (a 'dummy' treatment that does not contain any medicine but looks or tastes identical to the medicine being tested) to prevent bleeding to the brain.
What did we do?
We searched for studies that compared giving phenobarbital against no medicines. We compared and summarised the results of these studies and rated our confidence in the evidence, based on factors such as study methods and size.
What did we find?
We included 10 studies (792 babies).
The evidence suggests that phenobarbital has little to no effect in preventing bleeding to the brain. The evidence is very uncertain about the effect of phenobarbital on dilation of the ventricles in the brain and long-term development. The evidence suggests that phenobarbital has little to no effect in preventing deaths. We identified no ongoing trials.
What are the limitations of the evidence?
It is possible that people conducting the studies were aware of what treatment they were giving. Not all the studies provided data about everything that we were interested in. The studies were very small.
How up to date is this evidence?
This review updates our previous review. The evidence is up to date to January 2022.
The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH (any grade or severe) compared with control (i.e. no intervention or placebo). The evidence is very uncertain about the effects of phenobarbital on ventricular dilation or hydrocephalus and on neurodevelopmental impairment. The evidence suggests that phenobarbital results in little to no difference in death before discharge and all deaths during the study period compared with control.
Since 1993, no randomised studies have been published on phenobarbital for the prevention of IVH in preterm infants, and no trials are ongoing. The effects of postnatal phenobarbital might be assessed in infants with both neonatal seizures and IVH, in both randomised and observational studies. The assessment of benefits and harms should include long-term outcomes.
Intraventricular haemorrhage (IVH) is a major complication of preterm birth. Large haemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood in the newborn flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. It has been suggested that phenobarbital stabilises blood pressure and may protect against free radicals. This is an update of a review first published in 2001 and updated in 2007 and 2013.
To assess the benefits and harms of the postnatal administration of phenobarbital in preterm infants at risk of developing IVH compared to control (i.e. no intervention or placebo).
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, CINAHL and clinical trial registries in January 2022. A new, more sensitive search strategy was developed, and searches were conducted without date limits.
We included randomised controlled trials (RCTs) or quasi-RCTs in which phenobarbital was given within the first 24 hours of life to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birth weight below 1500 g or respiratory failure. Phenobarbital was compared to no intervention or placebo. We excluded infants with serious congenital malformations.
We used standard Cochrane methods. Our primary outcomes were all grades of IVH and severe IVH (i.e. grade III and IV); secondary outcomes were ventricular dilation or hydrocephalus, hypotension, pneumothorax, hypercapnia, acidosis, mechanical ventilation, neurodevelopmental impairment and death. We used GRADE to assess the certainty of the evidence for each outcome.
We included 10 RCTs (792 infants).
The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH of any grade compared with control (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.84 to 1.19; risk difference (RD) 0.00, 95% CI -0.06 to 0.07; I² for RD = 65%; 10 RCTs, 792 participants; low certainty evidence) and in severe IVH (RR 0.88, 95% CI 0.64 to 1.21; 10 RCTs, 792 participants; low certainty evidence).
The evidence is very uncertain about the effect of phenobarbital on posthaemorrhagic ventricular dilation or hydrocephalus (RR 0.62, 95% CI 0.31 to 1.26; 4 RCTs, 271 participants; very low certainty evidence), mild neurodevelopmental impairment (RR 0.57, 95% CI 0.15 to 2.17; 1RCT, 101 participants; very low certainty evidence), and severe neurodevelopmental impairment (RR 1.12, 95% CI 0.44 to 2.82; 2 RCTs, 153 participants; very low certainty evidence). Phenobarbital may result in little to no difference in death before discharge (RR 0.88, 95% CI 0.64 to 1.21; 9 RCTs, 740 participants; low certainty evidence) and mortality during study period (RR 0.98, 95% CI 0.72 to 1.33; 10 RCTs, 792 participants; low certainty evidence) compared with control.
We identified no ongoing trials.