Variability of serum indomethacin concentrations after oral and intravenous administration to preterm infants

Pharmacological Closure of Patent Ductus Arteriosus: Selecting the Agent and Route of Administration

Opinions are divided regarding the management of a persistently patent ductus arteriosus (PDA). Some of the adverse effects associated with a large hemodynamically significant duct, including prolonged ventilation, pulmonary hemorrhage, bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), and mortality, indicate that active management of infants with large ductal shunts may sometimes be necessary. Indomethacin and ibuprofen are the two US FDA-approved cyclooxygenase (COX) inhibitors used for the closure of a ductus in preterm babies. Both these drugs are effective in 70-80% of extremely low birthweight infants. Treatment with COX inhibitors may be associated with renal impairment, gastrointestinal hemorrhage, NEC, and spontaneous intestinal perforation when given concurrently with steroids, as well as changes in cerebrovascular auto-regulation. Ibuprofen appears to be a better choice for PDA closure, with a better side effect profile and efficacy that equals that of indomethacin. However, long-term outcome studies of ibuprofen are lacking, and prophylactic ibuprofen is ineffective in decreasing severe IVH. The choice of one drug over the other also depends on local availability of both drugs and the intravenous or enteral preparation. The oral preparation of ibuprofen appears as effective as the intravenous preparation. The use of paracetamol to close a hemodynamically significant PDA has increased in recent years. Paracetamol also decreases prostacyclin synthesis; however, unlike COX inhibitors, it does not have a peripheral vaso-constrictive effect and can be given to infants with contraindications to non-steroidal anti-inflammatory drugs. It appears to have similar efficacy based on limited data available from randomized trials. Until more data are available on efficacy, safety, and long-term outcomes, it cannot be recommended as the first choice.

Comparison of intravenous and enteral indomethacin administration for closure of patent ductus arteriosus in extremely-low-birth-weight infants

BACKGROUND

The objective of this retrospective cohort study was to compare the patent ductus arteriosus (PDA) closure rate with different routes (intravenous and enteral) of indomethacin treatment and neonatal outcomes.

METHODS

Infants with a birthweight < 1,000 g born between July 1997 and June 2007 at Taipei Veterans General Hospital and who received indomethacin treatment for PDA were included in the study. Outcome measures were ductal closure rate and neonatal outcomes.

RESULTS

Of 41 extremely-low-birth-weight infants with PDA, 3 infants had spontaneous closure and 3 died before treatment. Of the remaining 35 infants, 13 received enteral ethanol solution of indomethacin and 22 received the intravenous (IV) form. The total closure rates of the IV and enteral groups were 81.8% and 76.9%, respectively. There were no significant differences in the incidence of impaired renal function, necrotizing enterocolitis, chronic lung disease or severe retinopathy of prematurity between the 2 groups.

CONCLUSION

Our results suggest that ethanol-based indomethacin is an effective alternative to IV indomethacin for the pharmacological closure of PDA in extremely-low-birth-weight infants.

Furosemide in preterm infants treated with indomethacin for patent ductus arteriosus

OBJECTIVE

To evaluate the effect of furosemide on renal function and water balance in preterm infants treated with indomethacin (3 x 0.2 mg/kg at 12-h intervals) for symptomatic patent ductus arteriosus.

PATIENTS AND METHODS

We performed a retrospective multi-centre double cohort study in preterm infants <32 weeks of gestational age. Thirty-two infants treated with furosemide (1 mg/kg i.v.) before each indomethacin dose (furosemide group) were matched with 32 infants with indomethacin treatment alone (control-group). Renal effects (urine output, weight gain, serum creatinine, sodium concentration) were registered.

RESULTS

The study groups were comparable for gestational age, birth weight and day of therapy. Pretreatment differences were observed for urine output, weight and serum sodium. However, no differences were noticed in day-to-day urine output change or weight gain between the groups. A significant increase in serum creatinine concentration (50% vs. control, 18%; p < 0.05) and a concomitant significant decrease in serum sodium (-9 vs. control, -3 mmoL/L; p < 0.05) in the furosemide group was observed 72-96 h after starting therapy.

CONCLUSION

Furosemide before each indomethacin dose resulted in a significant increase in serum creatinine and hyponatremia, without increasing urine output.

Determination of indomethacin in plasma by micellar electrokinetic chromatography with UV detection for premature infants with patent ducts arteriosus

A simple and selective micellar electrokinetic chromatography (MEKC) is described for determination of indomethacin in plasma. Plasma proteins are precipitated by acetonitrile. An aliquot of supernatant was evaporated and reconstituted with Tris buffer for MEKC analysis. The separation of indomethacin was performed at 25 degrees C using a background electrolyte consisting of Tris buffer (30 mM; pH 8.0) with 100 mM sodium octanesulfonate (SOS) as an anionic surfactant. Under this condition, a good separation with high efficiency and short analysis time is achieved. Several parameters affecting the separation of indomethacin were studied, including pH and concentrations of the Tris buffer and SOS. The linear range of the method for the determination of indomethacin was over 0.3-10.0 microg/mL; the detection limit (signal-to-noise ratio=3; injection 0.5 psi 5s) was 0.1 microg/mL. The proposed method for determination of indomethacin in premature infants with patent ducts arteriosus has been demonstrated.

A rapid and sensitive microscale HPLC method for the determination of indomethacin in plasma of premature neonates with patent ductus arteriousus

Indomethacin (IND) is the drug of choice for the closure of a patent ductus arteriosus (PDA) in neonates. This paper describes a simple, sensitive, accurate and precise microscale HPLC method suitable for the analysis of IND in plasma of premature neonates. Samples were prepared by plasma protein precipitation with acetonitrile containing the methyl ester of IND as the internal standard (IS). Chromatography was performed on a Hypersil C(18) column. The mobile phase of methanol, water and orthophosphoric acid (70:29.5:0.5, v/v, respectively), was delivered at 1.5 mL/min and monitored at 270 nm. IND and the IS were eluted at 2.9 and 4.3 min, respectively. Calibrations were linear (r>0.999) from 25 to 2500 microg/L. The inter- and intra-day assay imprecision was less than 4.3 % at 400-2000 microg/L, and less than 22.1% at 35 microg/L. Inaccuracy ranged from -6.0% to +1.0% from 35 to 2000 microg/L. The absolute recovery of IND over this range was 93.0-113.3%. The IS was stable for at least 36 h when added to plasma at ambient temperature. This method is suitable for pharmacokinetic studies of IND and has potential for monitoring therapy in infants with PDA when a target therapeutic range for IND has been validated.

Furosemide for symptomatic patent ductus arteriosus in indomethacin-treated infants

BACKGROUND

Inhibition of prostaglandin synthesis mediates closure of the ductus arteriosus and renal side effects after indomethacin administration. Because furosemide increases prostaglandin production, it could potentially help prevent indomethacin-related toxicity but also decrease ductal response to indomethacin.

OBJECTIVES

The primary objectives of this review were to assess (1) whether furosemide affects the incidence of failure of ductal closure after indomethacin and that of indomethacin-related toxicity and (2) the effect of furosemide on mid-term and long-term outcome. The secondary objective was to determine whether the effect of furosemide on renal function and water balance depends on prior extracellular volume (assessed by blood urea nitrogen [BUN]/creatinine ratio).

SEARCH STRATEGY

We searched electronic databases (Medline, Embase and Cochrane) and selected abstract books, without language restriction.

SELECTION CRITERIA

We selected studies with (1) random allocation to either indomethacin alone or indomethacin and furosemide and (2) analysis of either short-term risk-benefit ratio of furosemide, mid- or long-term outcome, or the relationship between extracellular volume at study entry and changes in renal function.

DATA COLLECTION AND ANALYSIS

We assessed studies for possible bias and for quality of assessment of ductal patency. We assessed categorical variables using relative risk and absolute risk reduction. We assessed the effects of furosemide on renal function and fluid balance by comparing changes from baseline in the treatment group with those in controls. Subsets were determined a priori based on BUN/creatinine ratio at study entry.

MAIN RESULTS

All 3 studies fulfilling the entry criteria had limitations, including possible or definite bias. There was substantial heterogeneity among studies. Furosemide administration did not significantly increase the risk of failure of ductal closure; however, sample size was insufficient to rule out even a 31% increase. In the subset with initial BUN/creatinine ratio > 20 mg/mg, 2 of 18 patients receiving furosemide could not complete a 3-dose course of indomethacin because of toxicity. Minimal or no information was available about any of the other main outcome variables. Furosemide increased urine output regardless of the initial BUN/creatinine ratio, leading to a 5% weight loss during a 3-dose course, an undesired effect in patients with initial BUN/creatinine ratio > 20 mg/mg. Furosemide increased creatinine clearance only in patients with initial BUN/creatinine ratio <20 mg/mg.

REVIEWER'S CONCLUSIONS

There is not enough evidence to support the administration of furosemide to premature infants treated with indomethacin for symptomatic patent ductus arteriosus. Furosemide appears to be contraindicated in the presence of dehydration in those infants.

Drug disposition in neonates with patent ductus arteriosus

OBJECTIVE

To review the literature on the physiologic changes created by neonatal patent ductus arteriosus (PDA) and the potential impact on drug disposition in these infants.

DATA SOURCES

An Index Medicus and bibliographic search of the English-language literature pertaining to neonatal PDA and drug usage in newborns.

DATA SYNTHESIS

PDA in premature infants is associated with a variety of physiologic changes that could alter drug disposition. Perfusion of drug-elimination organs (i.e., liver and kidney) may be diminished, resulting in decreased drug elimination. Further, the general fluid overload state associated with PDA may result in larger volumes of distribution (Vd), and dilutional effects for many drugs. Drug absorption, Vd, tissue penetration, and clearance may be affected by the physiologic changes incurred by a PDA. Although the pharmacokinetics of several categories of therapeutic agents may be affected by a PDA, disposition changes with the aminoglycosides and indomethacin have been the best documented. The most reliable pharmacokinetic change appears to be related to drug Vd. The interpretation of many of these studies is confounded by a potential drug interaction with the concurrent administration of indomethacin for PDA closure.

CONCLUSIONS

Close therapeutic drug monitoring is indicated in newborns with PDAs as abrupt changes in drug disposition can occur with PDA closure. PDA-induced changes in specific pharmacokinetic parameters of agents such as the aminoglycosides, indomethacin, and perhaps vancomycin may prove to be a valuable diagnostic adjunct for the identification of babies with undiagnosed PDA. More research into this pharmacophysiologic aspect of pharmacokinetics is warranted.

Intravenous indomethacin therapy in preterm neonates with patent ductus arteriosus

This study examined the response of the patent ductus arteriosus (PDA) to intravenous Indomethacin using serial two dimensional and Doppler echocardiography and documented the complications associated with therapy. Thirty-six preterm neonates who were oxygen and ventilator dependent were studied when they were aged 3-7 days. The PDA initially closed in 22 (61%) and constricted in seven (19%) of the infants. It was non-responsive in five (14%) and the treatment was stopped because of complications in two (6%). Only three (43%) of seven neonates given a second course had PDA closure. In the 25 instances where there was PDA closure following Indomethacin, re-opening was documented echocardiographically on three (12%) occasions. Overall, Indomethacin therapy was successful in 29 (81%) neonates, PDA ligation was required in four (11%) and three died from unrelated causes. Three (8%) neonates developed major complications: multiple gastric perforations in the first, focal ileal perforation in the second, and necrotizing enterocolitis in the third. Treatment failure, PDA ligation and major complications occurred exclusively in neonates less than 28 weeks gestation. In view of the relatively low efficacy and high major complication rate in these extremely preterm infants, a randomized clinical trial needs to be conducted using two dimensional and Doppler echocardiography to allow accurate assessment of the PDA response to intravenous Indomethacin.

A high performance liquid chromatography method for the analysis of total and free indomethacin in serum

A simple rapid and sensitive HPLC technique for the analysis of total and free plasma indomethacin concentrations in neonates is described. The advantages of the technique are small sample volumes (50 microL) enabling the use of capillary samples, direct extraction, low limits of detection (20 ng/mL) and good precision (CV less than 7% between-batch). Indomethacin and the internal standard (flufenamic acid) eluted within 12 min and the peaks were unaffected by indomethacin metabolites or by a number of commonly used drugs. The technique is suitable for the investigation into the pharmacokinetics of total and free indomethacin, in neonates with patent ductus arteriosus, and could be used to define a therapeutic window for free indomethacin levels to enable therapeutic drug monitoring to occur in this condition.

Introduction of plasma indomethacin level monitoring and evaluation of an effective threshold level in very low birth weight infants with symptomatic patent ductus arteriosus

First results are described of individually tailored indomethacin dose rates employing on-line drug level monitoring for pharmacologically induced ductal constriction in very low birth weight infants with symptomatic patent ductus arteriosus (sPDA). In addition prolonged indomethacin therapy was introduced. From our data it appears that the effective threshold indomethacin level for the induction of ductus constriction has to be about 1000 ng/ml 10 h postdosing, while ductus closure can be maintained with a dose rate that exceeds a plasma level of 500 ng/ml for at least 1 week. These maintenance levels were also effective in completely suppressing the urinary metabolite excretion rates of PGI2 and PGE2, which are potential mediators of ductal relaxation. On-line indomethacin level monitoring appears to be practically essential for prolonged indomethacin therapy to overcome the marked variation of indomethacin disposition in preterm infants with sPDA.