Allopurinol for preventing mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy

Abstract

Background

Delayed neuronal death following a perinatal hypoxic insult is due partly to xanthine oxidase‐mediated production of cytotoxic free radicals. Evidence exists that allopurinol, a xanthine‐oxidase inhibitor, reduces delayed cell death in experimental models of perinatal asphyxia and in people with organ reperfusion injury.

Objectives

To determine the effect of allopurinol on mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy.

Search methods

We used the standard search strategy of the Cochrane Neonatal Group. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2012, Issue 1), MEDLINE (1966 to March 2012), EMBASE (1980 to March 2012), CINAHL (1982 to March 2012), conference proceedings, and previous reviews.

Selection criteria

Randomised or quasi‐randomised controlled trials that compared allopurinol administration versus placebo or no drug in newborn infants with hypoxic‐ischaemic encephalopathy.

Data collection and analysis

We extracted data using the standard methods of the Cochrane Neonatal Review Group with separate evaluation of trial quality and data extraction by two review authors.

Main results

We included three trials in which a total of 114 infants participated. In one trial, participants were exclusively infants with severe encephalopathy. The other trials also included infants with mild and moderately severe encephalopathy. These studies were generally of good methodological quality, but were too small to exclude clinically important effects of allopurinol on mortality and morbidity. Meta‐analysis did not reveal a statistically significant difference in the risk of death (typical risk ratio 0.88; 95% confidence interval (95% CI) 0.56 to 1.38; risk difference ‐0.04; 95% CI ‐0.18 to 0.10) or a composite of death or severe neurodevelopmental disability (typical risk ratio 0.78; 95% CI 0.56 to 1.08; risk difference ‐0.14; 95% CI ‐0.31 to 0.04).

Authors' conclusions

The available data are not sufficient to determine whether allopurinol has clinically important benefits for newborn infants with hypoxic‐ischaemic encephalopathy. Much larger trials are needed. Such trials could assess allopurinol as an adjunct to therapeutic hypothermia in infants with moderate and severe encephalopathy and should be designed to exclude important effects on mortality and adverse long‐term neurodevelopmental outcomes.

Plain language summary

Allopurinol for preventing mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy

Newborn infants who have been deprived of oxygen before, during, or after delivery (perinatal asphyxia) are at high risk of dying or developing brain damage. Studies using animal models suggest that allopurinol (a drug commonly used for preventing gout) can reduce the level of brain damage following perinatal asphyxia. Three small randomised controlled trials that examined whether giving allopurinol to newborn infants following perinatal asphyxia affected their outcomes were identified. None of these trials provided any evidence of benefit. Larger trials are needed to exclude important effects on survival and disability.

Background

Description of the condition

Hypoxic‐ischaemic encephalopathy is a major cause of death and of disability in newborn infants worldwide (Kurinczuk 2010). The severity of the encephalopathy predicts the risk of death and long‐term neurodevelopmental impairment (Sarnat 1976; Vannucci 1997; Gonzalez 2006). Brain damage following a perinatal hypoxic‐ischaemic insult occurs in two phases. Early cell death results from primary exhaustion of the cellular energy stores. A second phase of cell death occurs during reperfusion and reoxygenation several hours after the initial insult. The pathophysiology of late neuronal damage involves the production of cytotoxic free radicals (including hydrogen peroxide, superoxides, free iron and hydroxyl radicals) that damage cell lipids, proteins, and nucleic acids, and results in secondary energy failure, membrane dysfunction, and apoptosis (Inder 2000). The degree of secondary energy failure is predictive of mortality and neurodevelopmental impairment (Roth 1997). Various pharmacological and non‐pharmacological interventions that may limit free‐radical generation and minimise the extent of late cell death are the subject of other Cochrane reviews (Hunt 2002; McGuire 2004; Kecskes 2005; Beveridge 2006; Evans 2007; Jacobs 2007). With the exception of therapeutic mild hypothermia, none of these interventions has yet been proven to limit brain damage in newborn infants with hypoxic‐ischaemic encephalopathy (Edwards 2006; Jacobs 2007).

Description of the intervention

In part, the production of cytotoxic free radicals is dependent on xanthine oxidase‐mediated metabolism of hypoxanthine (Warner 2004). Studies using experimental animal models have found that the xanthine oxidase inhibitor allopurinol and its metabolic product, oxypurinol, reduce free‐radical formation and limit the degree of post‐asphyxia brain damage (Palmer 1990; Palmer 1991; Palmer 1993; Van Bel 1998). At high concentrations, allopurinol scavenges free radicals such as hydroxyl, chelates free iron, and inhibits lipid peroxidation and heat shock factor expression (Pacher 2006). Evidence from randomised controlled trials suggests that high‐dose allopurinol (> 10 mg/kg) reduces reperfusion injury in adults who undergo coronary bypass surgery (Johnson 1991; Sisto 1995). In newborn infants with severe respiratory failure needing treatment with extracorporeal membrane oxygenation, high‐dose allopurinol reduces free‐radical production and injury (Marro 1997). In infants with hypoplastic left heart syndrome who undergo cardiac surgery using deep hypothermic circulatory arrest, pretreatment with allopurinol reduces postoperative adverse cardiac and neurological outcomes (Clancy 2001).

The most commonly reported adverse effects of allopurinol are skin rashes and hypersensitivity reactions (Vazquez‐Mellado 2001). A very rare but severe hypersensitivity syndrome consisting of skin reactions (erythema multiforme, toxic epidermal necrolysis), fever, eosinophilia, and multiorgan failure has been described in people with concomitant renal impairment or thiazide diuretic use (Arellano 1993; Kumar 1996).

Why it is important to do this review

Given the evidence of beneficial effects in experimental models and in people with other forms of organ reperfusion injury, and the potential for allopurinol to affect pathogenic pathways associated with delayed neuronal death, we reviewed the available evidence from randomised controlled trials of allopurinol for newborn infants with hypoxic‐ischaemic encephalopathy to determine if there are any implications for current practice or for future research.

Objectives

To determine the effect of allopurinol on mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy.

Methods

Criteria for considering studies for this review

Types of studies

Controlled trials using either random or quasi‐random patient allocation.

Types of participants

Newborn infants (> 34 weeks' gestation) with hypoxic‐ischaemic encephalopathy defined as clinical evidence of cardiorespiratory or neurological depression (Apgar score < 7 at five minutes and beyond after birth) and/or evidence of severe metabolic acidosis in intrapartum foetal, umbilical arterial cord, or very early neonatal blood samples (pH < 7 or base deficit > 12 mmol/L), and/or clinical or electro‐encephalographic (multichannel or amplitude integrated) evidence of neonatal encephalopathy (MacLennan 1999).

Types of interventions

Allopurinol versus placebo or no drug administered within six hours of delivery. A minimum or maximum dose or duration of treatment was not pre‐specified. Allopurinol could have been given in conjunction with another intervention provided both treatment and control groups received the intervention.

Types of outcome measures

Primary outcomes

1. Death during infancy.

2. Death or severe neurodevelopmental disability in survivors assessed aged ≥ 12 months of age, defined as any one or combination of the following: non‐ambulant cerebral palsy, severe developmental delay assessed using validated tools, auditory and visual impairment (each component analysed individually as well as part of the composite outcome).

3. Cognitive and educational outcomes in survivors aged > 5 years old (intelligence quotient and/or indices of educational achievement measured using a validated assessment tool including school examination results).

Secondary outcomes

1. Seizures in the neonatal period, either apparent clinically or detected by electro‐encephalographic recordings.

2. Time to achieve full oral feeding independent of enteral tube feeding (days after birth), and/or incidence of continued enteral tube feeding at four weeks after birth.

3. Cortical, white matter, or basal ganglia abnormalities on brain imaging (magnetic resonance, computed tomography, or ultrasound).

4. Potential adverse effects of allopurinol (skin rashes, hypersensitivity reactions) that necessitates discontinuation of therapy.

Search methods for identification of studies

We used the standard search strategy of the Cochrane Neonatal Review Group

Electronic searches

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2012), MEDLINE (1966 to March 2012), EMBASE (1980 to March 2012), and CINAHL (1982 to March 2012) using a combination of the following text words and MeSH terms: [Infant, Newborn OR Asphyxia Neonatorum/ OR Hypoxia, Brain/ OR Brain Ischemia/ OR infant OR neonat*] AND [Allopurinol/ OR Free Radical Scavengers/ OR Free Radicals/ OR Antioxidants/]. The search outputs were limited with the relevant search filters for clinical trials as recommended in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We did not apply any language restriction.

We searched ClinicalTrials.gov and Current Controlled Trials for completed or ongoing trials.

Searching other resources

We examined the references in studies identified as potentially relevant. We also searched the abstracts from the annual meetings of the Pediatric Academic Societies (1993 to 2011), the European Society for Paediatric Research (1995 to 2011), the UK Royal College of Paediatrics and Child Health (2000 to 2012), and the Perinatal Society of Australia and New Zealand (2000 to 2012). We considered trials reported only as abstracts to be eligible if sufficient information was available from the report, or from contact with the authors, to fulfil the inclusion criteria.

Data collection and analysis

We used the standard methods of the Cochrane Neonatal Review Group.

Selection of studies

Two review authors screened the title and abstract of all studies identified by the above search strategy. We reassessed the full text of any potentially eligible reports and excluded those studies that did not meet all of the inclusion criteria. We discussed any disagreements until consensus was achieved.

Data extraction and management

We used a data collection form to aid extraction of relevant information from each included study. Two review authors extracted the data separately. We discussed any disagreements until consensus was achieved. We asked the investigators for further information if data from the trial reports were insufficient.

Assessment of risk of bias in included studies

We used the criteria and standard methods of the Cochrane Neonatal Review Group to assess the methodological quality of any included trials. Additional information from the trial authors was requested to clarify methodology and results as necessary. We evaluated and reported the following issues in the 'Risk of bias' tables:

1. Sequence generation: we categorised the method used to generate the allocation sequence as:

   1. low risk: any random process (e.g. random number table; computer random number generator);

   2. high risk: any non‐random process (e.g. odd or even date of birth; patient case‐record number);

   3. unclear.

2. Allocation concealment: we categorised the method used to conceal the allocation sequence as:

   1. low risk: (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);

   2. high risk: open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth;

   3. unclear.

3. Blinding: we assessed blinding of participants, clinicians, carers, and outcome assessors separately for different outcomes and categorised the methods as

   1. low risk;

   2. high risk;

   3. unclear.

4. Incomplete outcome data: we described the completeness of data including attrition and exclusions from the analysis for each outcome and any reasons for attrition or exclusion where reported. We assessed whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported or supplied by the trial authors, we re‐included missing data in the analyses. We categorised completeness as:

   1. low risk: < 20% missing data;

   2. high risk: ≥ 20% missing data;

   3. unclear.

Measures of treatment effect

We calculated risk ratio (RR) and risk difference (RD) for dichotomous data and weighted mean difference (WMD) for continuous data, with respective 95% confidence intervals (CI). We determined the number needed to treat for benefit (NNTB) or harm (NNTH) for analyses with a statistically significant difference in the RD.

Unit of analysis issues

The unit of analysis is the participating infant in individually randomised trials and the neonatal unit for cluster randomised trials.

Dealing with missing data

We contacted the trial primary investigators to seek missing data.

Assessment of heterogeneity

We examined the treatment effects of individual trials and heterogeneity between trial results by inspecting the forest plots. We calculated the I² statistic for each RR analysis to quantify inconsistency across studies and describe the percentage of variability in effect estimates that may be due to heterogeneity rather than sampling error. If substantial heterogeneity (I² > 50%) was detected, we explored the possible causes (e.g. differences in study design, participants, interventions, or completeness of outcome assessments).

Assessment of reporting biases

If data from more than five trials were included in a meta‐analysis, we examined a funnel plot for asymmetry.

Data synthesis

We used the fixed‐effect model in RevMan 5.1 (RevMan 2011) for meta‐analysis.

Subgroup analysis and investigation of heterogeneity

We specified these subgroup analyses:

1. Trials that assessed allopurinol as a sole therapy.

2. Trials of allopurinol as an adjunct to another therapy.

3. Severity of encephalopathy based on clinical features (Sarnat 1976):

• mild: hyperalertness, hyperreflexia, dilated pupils, tachycardia, absence of seizures

• moderate: lethargy, hyperreflexia, miosis, bradycardia, seizures, hypotonia with weak suck and Moro reflex

• severe: stupor, flaccidity, small mid‐position pupils that react poorly to light, decreased stretch reflexes, hypothermia, and absent Moro reflex

or nature of electroencephalogram (EEG) abnormality:

• mild: electrographic seizures, dysmaturity

• moderate: low voltage or discontinuous background

• severe: isoelectric or burst‐suppression pattern

Results

Description of studies

Three trials, in which a total of 114 infants participated, fulfilled eligibility criteria (van Bel 1998; Benders 2006; Gunes 2007). These studies were conducted between 1995 and 2005 in neonatal intensive care centres in The Netherlands and Turkey. This update includes additional neurodevelopmental outcome data from van Bel 1998 and Benders 2006.

Participants

The participants were term or late preterm infants with suspected perinatal asphyxia and hypoxic‐ischaemic encephalopathy. In one trial, only infants with severe encephalopathy, defined on the basis of abnormal findings on amplitude‐integrated EEG (aEEG), were eligible to participate (Benders 2006). In the other trials, infants with mild and moderately severe encephalopathy were also enrolled. Infants with major congenital anomalies or infections were excluded.

Interventions

In all of the studies, infants received the intervention or control within four hours after birth. Allopurinol was given intravenously in total daily doses of 40 mg/kg of birth weight. Benders 2006 and van Bel 1998 continued treatment for one day. Gunes 2007 continued treatment for three days after birth.

Outcomes

The trials reported short‐term outcomes including mortality, seizure frequency, neuro‐imaging findings, and biochemical measures of hepatic and renal function and assessed neurodevelopmental outcomes in surviving infants aged 18 months (Gunes 2007) and at four to eight years (van Bel 1998; Benders 2006).

Risk of bias in included studies

Although small, the trials were generally of good methodological quality with adequate allocation concealment (randomisation in central pharmacy, computer‐generated sequence in sealed opaque envelopes). One trial did not blind caregivers or assessors (van Bel 1998). All trials achieved complete or near‐complete follow‐up. Two trials reported intention‐to‐treat analyses. In Benders 2006, one infant who was diagnosed with a (probably genetic) condition associated with neurodevelopmental delay was excluded from analyses in the trial report. We have re‐included outcomes for this infant in intention‐to‐treat analyses in this review.

Effects of interventions

Allopurinol versus control (Comparison 1)

Primary outcomes: death and neurodevelopmental disability

Death during the neonatal period and during infancy (Outcome 1.1)

Meta‐analysis did not detect a statistically significant effect on death during the neonatal period or infancy: typical RR 0.88 (95% CI 0.56 to 1.38); typical RD ‐0.04 (95% CI ‐0.18 to 0.10) (3 studies; 114 infants); Figure 1.

1.

Forest plot of comparison: 1 Allopurinol versus control (placebo or no drug), outcome: 1.1 Death during the neonatal period and infancy.

Death or severe neurodevelopmental disability in survivors (Outcome 1.2 and Outcome 1.3)

Meta‐analysis did not detect a statistically significant effect on death or severe neurodevelopmental disability in survivors: typical RR 0.78 (95% CI 0.56 to 1.08); typical RD ‐0.14 (95% CI ‐0.31 to 0.04) (3 studies; 110 infants); Figure 2.

2.

Forest plot of comparison: 1 Allopurinol versus control (placebo or no drug), outcome: 1.2 Death or severe neurodevelopmental disability.

There was no statistically significant difference in the rate of severe quadriplegia in surviving infants: typical RR 0.59 (95% CI 0.28 to 1.27); typical RD ‐0.14 (95% CI ‐0.35 to 0.06) (3 studies; 73 infants); Figure 3.

3.

Forest plot of comparison: 1 Allopurinol versus control (placebo or no drug), outcome: 1.3 Severe quadriplegia in surviving infants.

Data were not available for neurosensory impairments or developmental indices.

Cognitive and educational outcomes

Not assessed in any of the trials.

Secondary outcomes: neonatal morbidity

Seizures in the neonatal period (Outcome 1.4)

Meta‐analysis did not detect a statistically significant effect on seizures in the neonatal period: typical RR 0.93 (95% CI 0.75 to 1.16); typical RD ‐0.05 (95% CI ‐0.21 to 0.11)(3 studies; 114 infants); Figure 4.

4.

Forest plot of comparison: 1 Allopurinol versus control (placebo or no drug), outcome: 1.4 Seizures during the neonatal period.

Time to achieve full oral feeding

Not reported by any of the trials.

Abnormalities on brain imaging (Outcome 1.5)

Only Benders 2006 reported this outcome. There was no statistically significant difference in the incidence of brain abnormalities assessed in the early neonatal period with ultrasound (RR 1.12; 95% CI 0.81 to 1.55; RD 0.10; 95% CI ‐0.17 to 0.36) or with magnetic resonance imaging in surviving infants (RR 1.88; 95% CI 0.56 to 6.31; RD 0.35; 95% CI ‐0.25 to 0.95); Figure 5.

5.

Forest plot of comparison: 1 Allopurinol versus control (placebo or no drug), outcome: 1.5 Abnormalities on brain imaging.

Potential adverse effects of allopurinol

Not assessed in any of the trials.

Subgroup analyses

1. Allopurinol as a sole therapy: all of the included trials assessed allopurinol as a sole therapy. 
 2. Allopurinol as an adjunct to another therapy: none of the included trials assessed allopurinol in combination with another therapy. 
 3. Severity of encephalopathy: meta‐analyses of outcome data from van Bel 1998 and Benders 2006 restricted to infants with severe encephalopathy defined by the detection of a burst suppression pattern or worse on aEEG at trial entry did not find statistically significant differences in mortality (Figure 1) or death or severe neurodevelopmental disability (Figure 2).

Gunes 2007 enrolled 19 infants with mild encephalopathy, 21 infants with moderately severe encephalopathy, and 20 infants with severe encephalopathy. Subgroup outcome data are not available.

Discussion

Summary of main results

There are limited data available from three small randomised controlled trials that assessed the effect of allopurinol in newborn infants with hypoxic‐ischaemic encephalopathy. These trials did not find any evidence of an effect on mortality, severe disability, neonatal seizure frequency, or the incidence of abnormalities on brain imaging during the neonatal period.

Overall completeness and applicability of evidence

Given the small number of infants who have participated in trials to date (n = 114), clinically important beneficial or harmful effects of allopurinol have not yet been excluded. Much larger trials similar to the efforts undertaken to assess the effect of therapeutic hypothermia for infants with hypoxic‐ischaemic encephalopathy would be needed to exclude modest but clinically important effect sizes (Jacobs 2007).

Quality of the evidence

Although small, the trials were generally of good methodological quality with adequate allocation concealment (randomisation in central pharmacy, computer‐generated sequence in sealed opaque envelopes). One trial did not blind caregivers or assessors (van Bel 1998). All trials achieved complete or near‐complete follow‐up neurodevelopmental assessment of survivors (Figure 6).

6.

'Risk of bias' graph: review authors' judgements about each 'Risk of bias' item presented as percentages across all included studies.

Authors' conclusions

Implications for practice.

The available data are insufficient to determine whether allopurinol is beneficial as an adjunctive treatment for newborn infants with hypoxic‐ischaemic encephalopathy. Modest but important effect sizes have not been excluded.

Implications for research.

Further large trials to determine the effect of allopurinol on mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy may be justified. Allopurinol is a simple and relatively inexpensive intervention. The biological plausibility for preventing hypoxic‐ischaemic injury has been well‐established in pre‐clinical studies and experiments using animal models (Warner 2004; Robertson 2012). The available data have not raised major safety concerns related to use in newborn infants. Trials in which other patient groups have participated have found some evidence of benefit in limiting tissue reperfusion injuries (Johnson 1991; Sisto 1995; Marro 1997; Clancy 2001).

Since evidence exists that mild systemic or head hypothermia reduces mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy (Jacobs 2007), allopurinol or any other therapies that aim to minimise delayed neuronal damage following perinatal asphyxia should be assessed as an adjunct to hypothermia in future trials (Perlman 2006). Hypothermia is thought to prevent neuronal death by reducing cellular metabolic rates and inhibiting multiple cytotoxic pathways including the generation of free radicals and the accumulation of hypoxanthine (Vannucci 1997). It is not known whether adjunctive specific inhibition of these pathways with allopurinol is of any additional or synergistic value (Robertson 2012). Furthermore, the effect of hypothermia on the pharmacokinetics of allopurinol and oxypurinol has not been explored (McGaurn 1994; van Kesteren 2006). Several other issues relating to trials of interventions for newborn infants with hypoxic‐ischaemic encephalopathy have been highlighted (Perlman 2006):

1. Inclusion criteria should be simple and pragmatic to allow the trial conclusions to be widely applicable, particularly to rural and remote settings and middle‐ and low‐income countries where the burden of hypoxic‐ischaemic encephalopathy is greatest (Kurinczuk 2010).

2. Infants with either moderate or severe neonatal encephalopathy should be eligible to participate since evidence exists that therapeutic hypothermia benefits infants in both of these prognostic categories (Jacobs 2007).

3. Trials should assess more than short‐term and surrogate outcomes. Since interventions that reduce mortality in infants with hypoxic‐ischaemic encephalopathy may result in higher rates of adverse neurological outcomes, long‐term follow‐up should be planned to assess the effect on neurodevelopmental and cognitive outcomes (Gonzalez 2006). A priori agreements between research groups on the use of standard neurodevelopmental assessments (as well as trial entry criteria and intervention dose and duration) would ease incorporation of data from future trials into meta‐analyses to improve precision of effect size estimates.

4. The 'therapeutic window' for minimising post‐asphyxial secondary neuronal death is less than about six hours after birth (Inder 2000). Approaching parents about their infant's participation in a clinical trial is very difficult during this time. Informing parents antenatally about the possible need for emergency intervention around the time of birth may help to increase recruitment rates without compromising parental understanding of the nature and purpose of the research. Research efforts have also examined the possibility of antenatal administration of allopurinol to women in labour where there is concern about perinatal asphyxia (Torrance 2009;Kaandorp 2010). It may be that transplacental allopurinol for compromised fetuses (perhaps with further doses given postnatally to infants with encephalopathy) is considered as a model for future evaluation.

What's new

Date	Event	Description
3 April 2012	New search has been performed	This updates the review 'Allopurinol for preventing mortality and morbidity in newborn infants with hypoxic‐ischaemic encephalopathy' (Chaudhari 2008).
3 April 2012	New citation required but conclusions have not changed	Updated search March 2012. No new trials identified but newly published additional neurodevelopmental outcome data from two trials included (Kaandorp 2012). No change to conclusions.

History

Protocol first published: Issue 4, 2007
 Review first published: Issue 2, 2008

Date	Event	Description
13 December 2007	Amended	Converted to new review format.

Data and analyses

Comparison 1. Allopurinol versus control (placebo or no drug).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Death during the neonatal period and infancy	3		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.1 All infants	3	114	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.56, 1.38]
1.2 Infants with severe encephalopathy	2	41	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.62, 1.51]
2 Death or severe neurodevelopmental disability	3		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
2.1 All infants	3	110	Risk Ratio (M‐H, Fixed, 95% CI)	0.78 [0.56, 1.08]
2.2 Infants with severe encephalopathy	2	41	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.66, 1.30]
3 Severe quadriplegia in surviving infants	3	73	Risk Ratio (M‐H, Fixed, 95% CI)	0.59 [0.28, 1.27]
4 Seizures during the neonatal period	3	114	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.75, 1.16]
5 Abnormalities on brain imaging	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
5.1 Cranial ultrasound	1	31	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.81, 1.55]
5.2 Magnetic resonance imaging (surviving infants)	1	9	Risk Ratio (M‐H, Fixed, 95% CI)	1.88 [0.56, 6.31]

1.1. Analysis.

Comparison 1 Allopurinol versus control (placebo or no drug), Outcome 1 Death during the neonatal period and infancy.

1.2. Analysis.

Comparison 1 Allopurinol versus control (placebo or no drug), Outcome 2 Death or severe neurodevelopmental disability.

1.3. Analysis.

Comparison 1 Allopurinol versus control (placebo or no drug), Outcome 3 Severe quadriplegia in surviving infants.

1.4. Analysis.

Comparison 1 Allopurinol versus control (placebo or no drug), Outcome 4 Seizures during the neonatal period.

1.5. Analysis.

Comparison 1 Allopurinol versus control (placebo or no drug), Outcome 5 Abnormalities on brain imaging.

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Benders 2006.

Methods	Randomised placebo‐controlled trial
Participants	Term newborn infants with evidence of perinatal asphyxia and severe neonatal encephalopathy (burst suppression pattern, or worse, on aEEG)
Interventions	Allopurinol (40 mg/kg intravenously) in 2 doses, within 4 hours after birth and 12 hours later (n = 17) versus placebo control (n = 15)
Outcomes	Mortality, changes in aEEG, abnormalities on brain ultrasound, and magnetic resonance imaging abnormal findings in surviving infants at discharge, and severe disability at 4 to 8 years defined as non‐ambulant cerebral palsy (Gross Motor Function Classification System levels III to V), epilepsy not responding to treatment, blindness, deafness with or without a full‐scale intelligence quotient < 70
Notes	The trial was stopped earlier than planned when an interim analysis had not detected any statistically significant effects. Follow up of this trial and the trial of van Bel 1998 was reported by Kaandorp 2012.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation	Low risk	Computer‐generated sequence
Allocation concealment	Low risk	Randomisation in central pharmacy
Blinding All outcomes	Low risk	Placebo‐controlled
Incomplete outcome data addressed All outcomes	Low risk	1 infant who was diagnosed with a (probably genetic) condition associated with neurodevelopmental delay was excluded from analyses in the trial reports but re‐included in intention‐to‐treat analyses in this review

Gunes 2007.

Methods	Method of randomisation not stated
Participants	Sixty asphyxiated infants were divided randomly into two groups
Interventions	Group I infants (n = 30) received allopurinol (40 mg/kg/day, 3 days) within 2 hours after birth. Group II infants (n = 30) received a placebo. Twenty healthy neonates served as control subjects
Outcomes	Cerebrospinal fluid and serum nitric oxide levels were measured within 0‐24 hours and 72‐96 hours after birth
Notes	Both serum and cerebrospinal fluid concentrations of nitric oxide were higher in severely asphyxiated infants (40.86 +/‐ 8.97, 17.3 +/‐ 3.63 micromol/L, respectively) but lower in mildly asphyxiated infants (25.85 +/‐ 3.57, 5.70 +/‐ 2.56 micromol/L, respectively) than in moderately asphyxiated infants (35.86 +/‐ 5.38, 11.06 +/‐ 3.37 micromol/L, respectively) within the first 0‐24 hours after birth. Serum nitric oxide levels in control subjects were lower than those of moderately and severely asphyxiated infants. Serum nitric oxide levels of Group I infants within 72‐96 hours after birth decreased significantly from their corresponding levels within 0‐24 hours after birth. The asphyxiated newborns treated with allopurinol had better neurologic and neurodevelopmental outcome at 12 or more months of age
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation	Low risk	Sequence generated using random number tables by person not involved with trial
Allocation concealment	Low risk	Sequentially numbered sealed opaque envelopes
Blinding All outcomes	Low risk	Placebo‐controlled
Incomplete outcome data addressed All outcomes	Low risk	2 infants in each group were lost to long‐term follow‐up. All had mild neonatal encephalopathy

van Bel 1998.

Methods	Method of randomisation not stated
Participants	Severely asphyxiated newborns; Eleven infants received 40 mg/kg ALLO intravenously, and 11 infants served as controls (CONT)
Interventions	High‐dose allopurinol (ALLO; 40 mg/kg)
Outcomes	Effect on free radical status in severely asphyxiated newborns and on post‐asphyxial cerebral perfusion and electrical brain activity Free radical status was assessed by serial plasma determination of non protein‐bound iron (microM), antioxidative capacity, and malondialdehyde (MDA; microM). Cerebral perfusion was investigated by monitoring changes in cerebral blood volume (delta CBV; mL/100 g brain tissue) with near infrared spectroscopy; electrocortical brain activity (ECBA) was assessed in microvolts by cerebral function monitor Plasma non protein‐bound iron, antioxidative capacity, and MDA were measured before 4 hours, between 16 and 20 hours, and at the second and third days of age. Changes in CBV and ECBA were monitored between 4 and 8, 16 and 20, 58 and 62, and 104 and 110 hours of age
Notes	Six CONT and two ALLO infants died after neurologic deterioration. No toxic side effects of ALLO were detected. Nonprotein‐bound iron (mean +/‐ SEM) in the CONT group showed an initial rise (18.7 +/‐ 4.6 microM to 21.3 +/‐ 3.4 microM) but dropped to 7.4 +/‐ 3.5 microM at day 3; in the ALLO group it dropped from 15.5 +/‐ 4.6 microM to 0 microM at day 3. Uric acid was significantly lower in ALLO‐treated infants from 16 hours of life on. MDA remained stable in the ALLO group, but increased in the CONT group at 8 to 16 hours versus < 4 hours (mean +/‐ SEM; 0.83 +/‐ 0.31 microM vs 0.50 +/‐ 0.14 microM). During 4 to 8 hours, delta CBV‐CONT showed a larger drop than delta CBV‐ALLO from baseline. During the subsequent registrations CBV remained stable in both groups. ECBA‐CONT decreased, but ECBA‐ALLO remained stable during 4 to 8 hours of age. Neonates who died had the largest drops in CBV and ECBA Follow up of this trial and the trial of Bender 2006 was reported by Kaandorp 2012
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation	Unclear risk	Method not stated
Allocation concealment	Low risk	Sequentially numbered sealed opaque envelopes
Blinding All outcomes	High risk	Unblinded
Incomplete outcome data addressed All outcomes	Low risk	Complete follow‐up

aEEG: amplitude‐integrated electroencephalogram; SD: standard deviation.

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Kaandorp 2010	Protocol for a randomised controlled trial of antenatal allopurinol in mothers with evidence of fetal hypoxia
Torrance 2009	Randomised controlled trial of antenatal allopurinol in mothers with evidence of fetal hypoxia

Differences between protocol and review

None.

Contributions of authors

Tejesvi Chaudhari and William McGuire developed the protocol, performed the electronic and hand searches, screened the title and abstract of all studies identified, and the full text of potentially relevant reports. Each author independently assessed the methodological quality of the included trials, extracted the relevant information and data, and completed the final review.

Sources of support

Internal sources

• HYMS & NIHR Centre for Reviews and Dissemination, University of York, UK.

External sources

• Eunice Kennedy Shriver National Institute of Child Health and Human Development National Institutes of Health, Department of Health and Human Services, USA.

  Editorial support of the Cochrane Neonatal Review Group has been funded with Federal funds from the Eunice Kennedy Shriver National Institute of Child Health and Human Development National Institutes of Health, Department of Health and Human Services, USA, under Contract No. HHSN275201100016C

Declarations of interest

None.

New search for studies and content updated (no change to conclusions)