ORIGINAL
`ARTICLES
`
`N-ACETYLCYSTEINE DOES NOT PREVENT BRONCHOPULMONARY
`DYSPLASIA IN IMMATURE INFANTS: A RANDOMIZED
`CONTROLLED TRIAL
`
`TERHI AHOLA, MD, RISTO LAPATTO, MD, PHD, KARI O. RAIVIO, MD, PHD, BO SELANDER, MD, LENNART STIGSON, MD,
`BALDVIN JONSSON, MD, PHD, FINN JONSBO, MD, GITTE ESBERG, MD, SO¨ REN STO¨ VRING, MD, SVEINN KJARTANSSON, MD, PHD,
`TOM STIRIS, MD, PHD, KRISTIN LOSSIUS, MD, KRISTINA VIRKOLA, MD, PHD, AND VINETA FELLMAN, MD, PHD
`
`Objective To evaluate whether N-acetylcysteine (NAC) infusion during the first week of life reduces the risk of death or
`bronchopulmonary dysplasia (BPD) in infants with extremely low birth weight.
`Study design In a Nordic multicenter, double-blind trial, infants (n = 391) weighing 500 to 999 g and on ventilator or nasal
`continuous positive airway pressure were randomized before the age of 36 hours to receive NAC 16 to 32 mg/kg/d (n = 194) or
`placebo (n = 197) intravenously for 6 days. Primary end points were death or BPD, defined as supplementary oxygen
`requirement at 36 weeks’ gestational age.
`Results There was no difference in the combined incidence of the primary end points death or BPD, 51% vs. 49%, between
`the NAC group and control group. Also similar was the incidence of BPD in survivors at 36 weeks’ gestational age, 40% vs. 40%,
`and the mean oxygen requirement at the age of 28 days, 31.2% vs. 30.7%, respectively. The severity of BPD was similar in both
`groups.
`Conclusions A 6-day course of intravenous N-acetylcysteine at the dosage used does not prevent BPD or death in infants
`with extremely low birth weight. (J Pediatr 2003;143:713-9)
`
`Antenatal glucocorticoids, surfactant replacement, and improved methods of
`
`intensive care and monitoring have markedly decreased the mortality of very
`preterm infants. However, bronchopulmonary dysplasia (BPD) remains an
`important cause of long-term morbidity after preterm birth.1 The pathogenesis of BPD
`is multifactorial, but among the key factors are oxygen therapy and inflammation. Both
`are known to induce increased production of reactive oxygen species and release of
`proinflammatory cytokines, which are capable of damaging cells and tissues as well as
`interfering with lung development. Appropriate ventilatory strategies to maintain optimal
`functional residual capacity, together with surfactant treatment, may reduce but not
`eliminate the risk of BPD.1,2 Glucocorticoids may acutely reduce ventilatory and oxygen
`requirements, but no long-term benefit in terms of BPD incidence and lung function in
`infants with extremely low birth weight has been shown, and an increased risk of brain
`damage as well as decreased growth has been reported.3 Evidence for inflammation,
`increased oxidant production, and oxidant-induced macromolecular damage has been
`demonstrated during the first week of life in infants developing BPD.1,4
`In contrast with many experimental animals, the enzymatic antioxidant defenses of
`preterm human neonates appear relatively well developed, with the exception of catalase.5
`However, immature infants have a relative glutathione deficiency, which increases with
`decreasing gestational age.6 Given the dual role of glutathione as a cosubstrate in
`peroxidase reactions and as a direct scavenger of reactive oxygen species, such a deficiency
`
`BPD
`IVH
`NAC
`
`Bronchopulmonary dysplasia
`Intraventricular hemorrhage
`N-acetylcysteine
`
`NEC
`PVL
`ROP
`
`Necrotizing enterocolitis
`Periventricular leukomalacia
`Retinopathy of prematurity
`
`See editorial, p 697.
`
`From the Hospital for Children and
`Adolescents,
`Helsinki
`University
`Central Hospital, Helsinki, Finland;
`and the University Hospitals of Lund,
`Gothenburg and Stockholm, Sweden;
`Copenhagen, Aarhus, and Aalborg,
`Denmark; Reykjavik,
`Iceland;
`and
`Oslo and Trondheim, Norway.
`Supported by grants from Helsinki
`University Central Hospital, the Fin-
`nish Pediatric Research Foundation,
`AstraZeneca, Sverige AB, the Pa¨ivikki
`and Sakari Sohlberg Foundation, and
`the Maud Kuistila Memorial Founda-
`tion.
`The N-acetylcysteine and placebo vials
`were supplied free of charge by Draco
`La¨kemedel AB (AstraZeneca, Sverige
`AB), Sweden.
`Submitted for publication Apr 4, 2003;
`revision received June 11, 2003; ac-
`cepted July 9, 2003.
`Reprint requests: Vineta Fellman, MD,
`PhD, Hospital for Children and Adol-
`escents, Helsinki University Central
`Hospital, PO Box 281, 00029 Hel-
`sinki, Finland. E-mail: vineta.fellman@
`helsinki.fi.
`Copyright ª 2003 Mosby, Inc. All rights
`reserved.
`0022-3476/2003/$30.00 + 0
`10.1067/S0022-3476(03)00419-0
`
`713
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`may impair antioxidant defenses. The synthesis of glutathi-
`one does not appear
`to be limited by the activity of
`c-glutamylcysteine synthetase even in preterm infants,7 but
`rather by the availability of cysteine. In this respect, preterm
`infants are at a disadvantage, because the transsulfuration
`pathway from methionine into cysteine is not functional as
`a result of deficient activity of cystathionase.8 During
`parenteral nutrition of immature infants, cysteine is the first
`amino acid to show decreased plasma levels.9
`Several trials of antioxidant treatment of preterm neo-
`nates to prevent BPD have been performed, with varying
`success. Neither vitamin A10 nor vitamin E11 has a consistent
`effect in the risk of BPD or death in infants with extremely low
`birth weight. Intratracheal administration of copper-zinc-
`superoxide dismutase did not reduce the incidence of BPD,
`but there was less pulmonary morbidity at age 1 year.12
`Given the important role of glutathione in antioxidant
`defense and the relative lack of glutathione in preterm infants,
`a rational approach to treatment would be to replenish
`glutathione stores. However, glutathione itself crosses cell
`membranes poorly, and its rate-limiting precursor, cysteine, is
`unstable in solutions.13 N-acetylcysteine (NAC) is a precur-
`sor of cysteine and is by itself a free radical scavenger.14
`Furthermore, it is available as a registered drug for intravenous
`use to treat acetaminophen poisoning. NAC enters the cell
`and is deacetylated to cysteine,15 which can replenish intra-
`cellular glutathione. NAC treatment reduced lung injury in
`adults with adult respiratory distress syndrome in some
`studies,16,17 but not in others.18
`We hypothesized that NAC would decrease morbidity
`and mortality in preterm infants because of
`its direct
`antioxidant effects and its ability to increase intracellular
`glutathione concentrations. The aim of this study was to
`evaluate whether NAC infusion during the first week of life
`reduces the risk of death or BPD in infants with extremely low
`birth weight.
`
`METHODS
`randomized, double-blind, placebo-controlled,
`This
`multicenter trial was performed in 10 academic neonatal
`intensive care units in Denmark, Finland, Iceland, Norway,
`and Sweden between March 1997 and April 2001. The
`research ethics committees of each institution and the
`National Agencies for Medicines in each country approved
`the protocol. Informed parental consent was obtained for each
`infant. Randomization was stratified for each center in blocks
`of 10 patients.
`Infants with birth weights of 500 to 999 g who were on
`ventilator or nasal continuous positive airway pressure were
`eligible for enrollment before the age of 36 hours. Children
`with major congenital anomalies were excluded.
`The infants were randomized either to intravenous
`NAC or to placebo group. For the first 67 patients, the
`preparations were Parvolex (N-acetyl-L-cysteine; 200 mg/
`mL, Evans, UK), or 0.9% sodium chloride. The remainder
`received Mucomyst (N-acetyl-L-cysteine; 200 mg/mL) or its
`
`solvent without NAC, manufactured in identical vials by
`Draco La¨kemedel AB, Lund, Sweden. Sets of 10 vials for each
`patient were numbered by the Pharmacy of Helsinki
`University Central Hospital for each center according to the
`randomization list and were used in consecutive order. The
`NAC vials were diluted 1:100 to a final concentration of 2 mg/
`mL with 5% to 30% glucose solution, depending on the
`glucose requirement of the infant. The dilution procedure for
`the placebo infusion was identical. The infusion was started
`before the age of 36 hours and lasted for 6 days at a constant
`rate of 16 to 32 mg/kg/d, which was calculated on the basis of
`birth weight, with the smallest infants receiving the lowest
`dosages. This dosage was based on the results of our phar-
`macokinetic study of intravenous NAC in preterm babies19
`and aimed at a steady-state plasma concentration of 100 to
`300 lmol/L. The target concentration was based both on
`a clinical study in adults with myocardial infarction20 and on
`our unpublished work on cultured cells exposed to oxidants.
`The patients were treated according to the routine procedures
`in each intensive care unit and received parenteral and usually
`some enteral nutrition. Intravenous amino acids (Vaminolac,
`Fresenius-Kabi, Uppsala, Sweden, containing 1 mg/mL
`cysteine + cystine) were started on day 1 or 2, with the first
`dose 8 mL/kg/d, increasing daily to as much as 40 to 60 mL/
`kg/d. Ultrasound examinations of the brain were performed at
`least once during the first week and at the age of 28 days. To
`describe the radiological severity of BPD, chest radiographs
`were taken at the ages of 28 days and 36 gestational weeks and
`classified according to Weinstein et al21 and Toce et al22 by
`one radiologist. To ensure compliance and to evaluate drug
`metabolism plasma NAC, cysteine, and glutathione con-
`centrations were assayed by using a high-performance liquid
`chromatography method with penicillamine as the internal
`standard.23 In short, disulfides were first reduced by dithio-
`threitol to free sulfhydryls, which were then derivatized with
`monobromobimane. Hence, the values we report here are for
`total NAC and total cysteine, which include various NAC and
`cysteine-containing disulfides in addition to free monomeric
`NAC and cysteine. A reversed-phase C-18 column was used
`to separate the adducts, and quantitation was performed by
`using a fluorescence detector.
`To detect possible side effects caused by NAC, laboratory
`tests, including hemoglobin, white blood cell count, throm-
`bocytes, alanine aminotransferase, international standardized
`ratio of thromboplastin time, and serum urea level were
`followed during the first 2 weeks. Blood pressure, heart rate,
`and oxygen saturation were monitored continuously during the
`study period, with special attention to the mean arterial blood
`pressure during 1 hour before and the first 6 hours after the start
`of the infusion. Relevant complications were recorded daily
`according to the requirements of the drug company.
`The primary outcome was death by 36 gestational weeks
`or BPD, defined as any supplementary oxygen requirement at
`36 gestational weeks. The severity of BPD was classified
`according to a recent proposal.1 Secondary outcome measures
`were requirement of supplemental oxygen at the age of 28
`days, duration of ventilator or nasal continuous positive airway
`
`714 Ahola et al
`
`The Journal of Pediatrics  December 2003
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`Table I. Baseline characteristics of infants according
`to treatment assignment*
`
`Characteristic
`
`Antenatal
`glucocorticoid therapy
`Pre-eclampsia
`Maternal infection
`Outborn
`Vaginal delivery
`Male gender
`Small for gestational
`age (<ÿ2 SD)
`Respiratory distress
`syndrome
`Surfactant treatment
`
`NAC
`(n = 194)
`n (%)
`
`Placebo
`(n = 197)
`n (%)
`
`171 (89)
`
`175 (89)
`
`48 (25)
`70 (36)
`23 (12)
`83 (43)
`95 (49)
`55 (28)
`
`57 (29)
`61 (31)
`15 (8)
`79 (40)
`99 (50)
`67 (34)
`
`166 (86)
`
`166 (84)
`
`143 (74)
`
`132 (67)
`
`Mean (SD) Mean (SD)
`
`Age of mother, y
`Birth weight, g
`Gestational age, wk
`Apgar score
`1 min
`5 min
`Age at starting treatment, h
`Respiratory status before treatment
`Fraction of inspired oxygen
`Mean airway pressure, cm H2O
`Oxygenation index
`
`29.8 (5.5)
`776 (128)
`26.3 (1.7)
`
`5.4 (2.7)
`7.4 (2.2)
`23.4 (8.6)
`
`.30 (.11)
`7.6 (2.9)
`.35 (.34)
`
`30.2 (4.7)
`780 (134)
`26.5 (1.8)
`
`5.5 (2.4)
`7.7 (1.8)
`24.1 (8.9)
`
`.30 (.11)
`7.3 (2.5)
`.33 (.24)
`
`*Data are presented as percentages and means (SDs). There were no
`significant differences between the groups.
`
`pressure treatment, weight gain, and the incidence of other
`reactive oxygen species-related diseases:
`intraventricular
`hemorrhage (IVH) classified according to the criteria of
`Papile et al,24 periventricular leukomalacia (PVL) according to
`the criteria of Trounce et al,25 necrotizing enterocolitis (NEC)
`grade III or higher
`(NEC needing surgical
`treatment)
`according to Bell et al,26 and retinopathy of prematurity
`(ROP) classified as the stage of disease in the more severely
`affected eye, based on the International Classification of
`Retinopathy of Prematurity.27
`Our sample size calculation was based on the statistics
`during a 2-year period of 1993 to 1995 in the Hospital for
`Children and Adolescents, Helsinki University Central
`Hospital, which showed that 46% of babies weighing <1000
`g at birth either died or developed BPD by the time they
`reached the age of 36 gestational weeks. To detect a 33%
`reduction in BPD or death with NAC treatment with a power
`of 80% and a level of significance of 5% with a two-tailed test,
`the sample size was estimated to be 180 in each group.
`All data for eligible enrolled infants were analyzed on an
`intention-to-treat basis. Baseline data for the treatment
`
`N-Acetylcysteine Does Not Prevent Bronchopulmonary Dysplasia
`in Immature Infants: A Randomized Controlled Trial
`
`Figure. The severity of BPD, classified as mild, moderate, or severe
`according to Jobe and Bancalari.1 One patient in the placebo group
`was lost to follow-up, and definite classification could not be
`performed.
`
`groups were compared by using the t test for continuous
`variables or the Mann-Whitney U test, as appropriate.
`Categorical baseline characteristics and outcomes were
`analyzed by using the v2 test. All statistical tests were two-
`tailed. Logistic regression was used to analyze the outcomes.
`Data were analyzed by using the SPSS 10.0 statistical package
`(SPSS, Inc, Chicago, Ill).
`
`RESULTS
`A total of 397 infants were enrolled in the study, but six
`infants were excluded from the analyses, one because of
`parental refusal and five because of major congenital anomalies
`diagnosed after the enrollment (one transposition of great
`arteries, two tetralogy of Fallot, one major ventricular septal
`defect, and one anal atresia). After the exclusion of these
`infants, 391 infants participated in the study: 194 in the NAC
`group and 197 in the placebo group. In two cases, the infusion
`was discontinued because of dosage error, and the code was
`opened (one NAC, one placebo). These cases are included in
`the analyses. There were no statistically significant differences
`in the baseline characteristics between the treatment groups
`(Table I).
`There was no difference in the primary outcome of
`death or BPD at the age of 36 gestational weeks between the
`NAC and placebo groups (Table II). In the NAC group, 51%
`of the infants had BPD or had died, compared with 49% of
`infants in the placebo group (odds ratio, 1.0; 95% confidence
`interval, .7-1.6). Mortality at the age of 36 gestational weeks
`between the groups did not differ significantly: 18% in the
`NAC group, 14% in the placebo group. The incidence of BPD
`in infants alive at 36 gestational weeks was also similar. The
`severity of BPD was similar in the NAC and placebo group
`(Figure). When the infants were divided into two subgroups
`according to their birth weight (cutoff, 750 g; Table II) or
`gestational age (cutoff, 27 weeks; data not shown), no
`significant differences were noted in the incidence of BPD
`or death between the NAC or placebo treatments.
`
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`Table II. Primary and secondary outcome measures: odds ratio of BPD or death at the age of 36 gestational
`weeks and oxygen dependency or death at the age of 28 days
`
`Outcome
`
`NAC, %
`n/total (%)
`
`Placebo, %
`n/total (%)
`
`Odds ratio
`(95% confidence interval)
`
`P value
`
`At the age of 36 gestational weeks
`BPD or death
`Birth weight 500–750 g
`Birth weight 751–999 g
`BPD
`Birth weight 500–750 g
`Birth weight 751–999 g
`Death
`Birth weight 500–750 g
`Birth weight 751–999 g
`
`At the age of 28 days
`Oxygen supplementation or death
`All infants
`Birth weight 500–750 g
`Birth weight 751–999 g
`Oxygen supplementation
`Birth weight 500–750 g
`Birth weight 751–999 g
`Death
`Birth weight 500–750 g
`Birth weight 751–999 g
`
`98/194 (51)
`57/84 (68)
`41/110 (37)
`64/160 (40)
`35/62 (56)
`29/98 (30)
`34/194 (18)
`22/84 (26)
`12/110 (11)
`
`167/194 (86)
`80/84 (95)
`87/110 (79)
`138/165 (84)
`59/63 (94)
`79/102 (77)
`29/194 (15)
`21/84 (25)
`8/110 (7)
`
`96/196 (49)
`52/87 (60)
`44/109 (40)
`68/168 (40)
`34/69 (49)
`4/99 (34)
`28/197 (14)
`18/88 (20)
`10/109 (9)
`
`164/197 (83)
`82/88 (93)
`82/109 (75)
`141/174 (81)
`66/72 (92)
`75/102 (74)
`23/197 (12)
`16/88 (18)
`7/109 (6)
`
`1.1 (.7–1.6)
`1.4 (.8–2.7)
`.9 (.5–1.5)
`1.0 (.6–1.5)
`1.3 (.7–2.6)
`.8 (.4–1.5)
`1.3 (.7–2.2)
`1.4 (.7–2.8)
`1.2 (.5–2.9)
`
`1.2 (.7–2.2)
`1.5 (.4–5.4)
`1.2 (.7–2.3)
`1.2 (.7–2.1)
`1.3 (.4–5.0)
`1.2 (.7–2.3)
`1.3 (.7–2.4)
`1.5 (.7–3.1)
`1.1 (.4–3.3)
`
`.76
`.27
`.64
`.93
`.41
`.48
`.37
`.38
`.67
`
`.44
`.57
`.50
`.53
`.66
`.52
`.34
`.28
`.80
`
`At the age of 28 days, there was no significant difference
`in mortality or need of supplemental oxygen. Also, the mean
`percentage of oxygen required at the age of 28 days was
`similar: 31.2% in the NAC group and 30.7% in the placebo
`group. There was no statistically significant difference in the
`need of respiratory support between the groups. The median
`duration of ventilator treatment was 5 and 6 days, the median
`duration of nasal continuous positive airway pressure treat-
`ment was 24 and 27 days, and the median duration of any
`mechanical respiratory support was 37 and 42 days in the
`NAC and placebo groups, respectively.
`The incidences of the other outcome measures are
`presented in Table III. There were no significant differences in
`the incidence of IVH, NEC, patent ductus arteriosus, PVL, or
`ROP between the two groups, ascertained at death or at the
`age of 36 gestational weeks. Also, the weight gain from birth
`to the age of 36 gestational weeks was similar in both groups.
`The use of postnatal steroids did not differ between the NAC
`and placebo groups.
`Chest radiographs were taken of 260 infants at the age
`of 28 days and in 230 infants at the age corresponding to 36
`gestational weeks. No difference was found at either age: the
`scores according to Weinstein et al21 at 36 weeks were 3.0 ±
`1.3 and 2.9 ± 1.2 and the scores according to Toce et al22 were
`4.4 ± 2.0 and 4.1 ± 1.8 in the NAC and placebo groups,
`respectively.
`In the patient group receiving NAC, the mean plasma
`concentration of NAC was 170 lmol/L (range, 0-548 lmol/
`
`L) on day 3 and 172 lmol/L (range, 0-351 lmol/L) on day 7,
`just before the 6-day infusion was stopped. On day 3, the mean
`plasma cysteine concentration was 108 lmol/L (range, 46-243
`lmol/L) in the NAC group and 125 lmol/L (range, 44-253
`lmol/L) in the placebo group (P = .01). On day 7, the mean
`plasma cysteine level was 144 lmol/L (range, 37-358 lmol/L)
`and 169 lmol/L (range, 40-390 lmol/L) in the NAC and
`placebo groups, respectively (P = .02). Although there was
`a difference between the group means, the increase in the
`plasma cysteine concentration from day 3 to day 7 was similar.
`The mean plasma glutathione concentrations were 19 lmol/L
`(range, 2-68 lmol/L) and 21 lmol/L (range, 2-59 lmol/L) on
`day 3, and 19 lmol/L (range, 2-33 lmol/L) and 23 lmol/L
`(range, 2-51 lmol/L) on day 7 in the NAC and placebo
`groups, respectively.
`No differences were found between the treatment
`groups in blood pressure or in laboratory tests during the first
`2 weeks of life. No adverse effects were observed that could be
`ascribed to NAC.
`
`DISCUSSION
`Our trial showed that a 6-day course of intravenous
`NAC did not prevent death or bronchopulmonary dysplasia in
`infants with extremely low birth weight. The reasons for this
`outcome can be sought either in a faulty basic rationale for the
`study or in the design and implementation of the trial. An
`
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`Table III. Main neonatal diagnoses in NAC and placebo groups
`
`Outcome
`
`Patent ductus arteriosus
`Indomethacin-treated
`Operated
`Intraventricular hemorrhage
`Any grade
`Severe (grade 3–4)
`Periventricular leukomalacia
`In all examined
`In survivors
`Retinopathy of prematurity
`Any grade
`Severe (grade $3)
`Necrotizing enterocolitis (operated)
`Sepsis (positive blood culture)
`
`NAC
`n/total (%)
`
`107/188 (57)
`84/188 (45)
`23/188 (12)
`
`50/193 (26)
`22/192 (11)
`
`15/193 (8)
`12/160 (8)
`
`72/161 (45)
`20/161 (12)
`17/194 (9)
`64/186 (34)
`
`Placebo
`n/total (%)
`
`102/193 (53)
`81/193 (42)
`21/193 (11)
`
`46/195 (24)
`19/195 (10)
`
`21/195 (11)
`16/169 (9)
`
`86/171 (50)
`20/171 (12)
`16/197 (8)
`64/193 (33)
`
`Odds ratio
`(95% confidence interval)
`
`P value
`
`1.2 (.8–1.8)
`1.1 (.8–1.7)
`1.1 (.6–2.2)
`
`1.1 (.7–1.8)
`1.2 (.6–2.3)
`
`.7 (.3–1.4)
`.8 (.4–1.7)
`
`.8 (.5–1.2)
`1.1 (.6–2.1)
`1.1 (.5–2.2)
`1.1 (.7–1.6)
`
`.40
`.56
`.67
`
`.60
`.58
`
`.31
`.52
`
`.31
`.84
`.82
`.80
`
`optimal strategy to prevent lung injury should be based on an
`understanding of its pathogenesis.
`In the infant with extremely low birth weight, structural
`immaturity and surfactant deficiency necessitate mechanical
`ventilation and oxygen administration, both of which contrib-
`ute to an inflammatory response. Oxidative stress in preterm
`infants is indicated by lower reduced and higher oxidized
`glutathione concentrations in plasma of preterm infants
`compared with term infants,28 and lower reduced glutathione
`levels in tracheal aspirates of preterm infants developing
`BPD.29
`Glutathione peroxidase is important for removal of
`intracellular hydrogen peroxide and lipid peroxides, and
`glutathione is a direct scavenger of oxidants both intracellu-
`larly and extracellularly. Its role in lung protection is suggested
`by the high concentrations of glutathione in the lining fluid of
`lower airways and alveoli, with a transient postnatal decrease
`in preterm infants.6 NAC may not be the most effective
`glutathione precursor, but it is available as a registered drug.
`Furthermore, NAC itself is a potent scavenger of the hydroxyl
`radical and hypochlorous acid, is somewhat slower to react
`with hydrogen peroxide, and is unreactive with superoxide.30
`In animal experiments, intraperitoneally administered
`NAC ameliorated hyperoxic lung injury in guinea pigs.31
`Lipopolysaccharide-induced lung damage in rats was also
`attenuated by NAC, apparently because of scavenging of free
`radicals and inhibition of neutrophil oxidant production.32
`Human studies of both the biochemical and clinical effects of
`NAC have been inconclusive or conflicting, but the trials have
`been small. In adult respiratory distress syndrome, NAC
`improved oxygenation and lung function but had no sig-
`nificant effect on mortality.16,17 Apart from acetaminophen
`poisoning and genetic disorders of glutathione metabolism,
`intravenous NAC has not been studied in children. A clinical
`trial to test the applicability of NAC for prevention of BPD
`thus seemed warranted.
`
`N-Acetylcysteine Does Not Prevent Bronchopulmonary Dysplasia
`in Immature Infants: A Randomized Controlled Trial
`
`The subjects of our trial, infants weighing <1000 g at
`birth, represent a high-risk group with respect to the primary
`outcome measures, and a reasonable one third reduction in the
`incidence of death or BPD was the basis for sample size
`calculation. The target number of patients was recruited, and
`thus, a significant effect of NAC on these outcomes was ruled
`out. However, because the incidence of other complications of
`immaturity is lower, potential beneficial effects of NAC on
`IVH, NEC, PVL, and ROP cannot be evaluated on the basis
`of this trial, even though the incidence of PVL was 39% higher
`in the control group than in the NAC group. A considerably
`larger trial would be required to demonstrate a beneficial effect
`of NAC on hypoxic-ischemic brain injury in newborn infants,
`which has been shown in experimental animals.33
`N-acetylcysteine infusion was timed over the 6-day
`period, during which several biochemical indicators of oxidant
`effects increase in plasma,34 in tracheal aspirates,35 and expired
`air.36 The largest change in the oxygen environment of the
`infant occurs immediately after birth, and usually at that time,
`ventilatory assistance is also initiated. An earlier start of NAC
`treatment could therefore have been more effective, but on the
`other hand, the trial would have recruited several infants who
`were weaned from the ventilator by age 36 hours. Whether
`a longer intervention could have been effective remains
`unclear.
`To scavenge free radicals effectively and provide sub-
`strate for glutathione synthesis, an adequate dose of NAC
`must be given. There are no guidelines for the use of NAC
`in immature infants, and the desired therapeutic effect must
`be weighed against the risk of side effects. The dosage regi-
`men based on our pharmacokinetic study19 succeeded in
`maintaining the target concentration of 200 lM in most of the
`infants. Whether a higher dose would have influenced the
`primary outcome measures is a matter of speculation. Side
`effects noted in patients treated for acetaminophen poisoning
`include hypotension, bronchospasm, and a decrease in blood
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`coagulation factors, but no adverse effects attributable to NAC
`were observed in our trial.
`The scavenging function of NAC is exerted by the intact
`molecule, but it must be deacetylated to cysteine to act as
`a glutathione precursor. Adult human liver and endothelial
`cells are able to deacetylate NAC,37 but there is no infor-
`mation on the development of N-acetylase activity in any
`human tissue. Because in our study the change in plasma
`total cysteine concentration during the NAC infusion did not
`differ from that in the placebo infants, intravenous NAC may
`be poorly deacetylated in preterm infants. In a study of
`intravenous amino acid solutions for preterm infants, more
`than half of the NAC dose was excreted unchanged, and it had
`no demonstrable effect on plasma cysteine levels.38 Our
`unpublished studies have shown that NAC is able to reduce
`cysteine from cystine and from mixed disulfides. Thus, even if
`NAC itself were a poor substrate for glutathione synthesis, its
`potential benefits as an antioxidant would depend on its ability
`to scavenge oxidants chemically and to liberate cysteine from
`disulfides. Glutathione is mainly intracellular, and the goal for
`NAC treatment was to increase glutathione concentration in
`the cells. This could unfortunately not be studied. NAC
`infusion did not increase plasma glutathione or cysteine
`concentrations. The question remains open whether in-
`terventions increasing intracellular glutathione levels protect
`from the development of BPD.
`In conclusion, no beneficial effects of NAC with the
`dosage used could be demonstrated at 36 weeks. An on-
`going follow-up of the surviving infants will show whether
`the long-term pulmonary outcome can be improved with early
`NAC treatment, as was recently reported for infants treated at
`birth with recombinant human CuZn superoxide dismutase.12
`
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