Glyceryl-1-nitrate pharmacokinetics in healthy volunteers

Nitroglycerin for treatment of retained placenta: A randomised, placebo-controlled, multicentre, double-blind trial in the UK

BACKGROUND

Retained placenta following vaginal delivery is a major cause of postpartum haemorrhage. Currently, the only effective treatments for a retained placenta are the surgical procedures of manual removal of placenta (MROP) and uterine curettage, which are not universally available, particularly in low- and middle-income countries. The objective of the trial was to determine whether sublingual nitroglycerin spray was clinically effective and cost-effective for medical treatment of retained placenta following vaginal delivery.

METHODS AND FINDINGS

A randomised, placebo-controlled, double-blind trial was undertaken between October 2014 and July 2017 at 29 delivery units in the UK (Edinburgh, Glasgow, Manchester, Newcastle, Preston, Warrington, Chesterfield, Crewe, Durham, West Middlesex, Aylesbury, Furness, Southampton, Bolton, Sunderland, Oxford, Nottingham [2 units], Burnley, Chertsey, Stockton-on-Tees, Middlesborough, Chester, Darlington, York, Reading, Milton Keynes, Telford, Frimley). In total, 1,107 women with retained placenta following vaginal delivery were recruited. The intervention was self-administered 2 puffs of sublingual nitroglycerin (800 μg; intervention, N = 543) or placebo spray (control, N = 564). The primary clinical outcome was the need for MROP, assessed at 15 minutes following administration of the intervention. Analysis was based on the intention-to-treat principle. The primary safety outcome was measured blood loss between study drug administration and transfer to the postnatal ward or other clinical area. The primary patient-sided outcomes were satisfaction with treatment and side-effect profile, assessed by questionnaires pre-discharge and 6 weeks post-delivery. Secondary clinical outcomes were measured at 5 and 15 minutes after study drug administration and prior to hospital discharge. There was no statistically significant or clinically meaningful difference in need for MROP by 15 minutes (primary clinical outcome, 505 [93.3%] for nitroglycerin versus 518 [92.0%] for placebo, odds ratio [OR] 1.01 [95% CI 0.98-1.04], p = 0.393) or blood loss (<500 ml: nitroglycerin, 238 [44.3%], versus placebo, 249 [44.5%]; 500 ml-1,000 ml: nitroglycerin, 180 [33.5%], versus placebo, 224 [40.0%]; >1,000 ml: nitroglycerin, 119 [22.2%], versus placebo, 87 [15.5%]; ordinal OR 1.14 [95% CI 0.88-1.48], p = 0.314) or satisfaction with treatment (nitroglycerin, 288 [75.4%], versus placebo, 303 [78.1%]; OR 0.87 [95% CI 0.62-1.22], p = 0.411) or health service costs (mean difference [£] 55.3 [95% CI -199.20 to 309.79]). Palpitations following drug administration were reported more often in the nitroglycerin group (36 [9.8%] versus 15 [4.0%], OR 2.60 [95% CI 1.40-4.84], p = 0.003). There were 52 serious adverse events during the trial, with no statistically significant difference in likelihood between groups (nitroglycerin, 27 [5.0%], versus placebo, 26 [4.6%]; OR 1.13 [95% CI 0.54-2.38], p = 0.747). The main limitation of our study was the low return rate for the 6-week postnatal questionnaire. There were, however, no differences in questionnaire return rates between study groups or between women who did and did not have MROP, with the patient-reported use of outpatient and primary care services at 6 weeks accounting for only a small proportion (approximately 5%) of overall health service costs.

CONCLUSIONS

In this study, we found that nitroglycerin is neither clinically effective nor cost-effective as a medical treatment for retained placenta, and has increased side effects, suggesting it should not be used. Further research is required to identify an effective medical treatment for retained placenta to reduce the morbidity caused by this condition, particularly in low- and middle-income countries where surgical management is not available.

TRIAL REGISTRATION

ISRCTN.com ISRCTN88609453 ClinicalTrials.gov NCT02085213.

Nitroglycerin for management of retained placenta

BACKGROUND

Retained placenta affects 0.5% to 3% of women following delivery, with considerable morbidity if left untreated. Use of nitroglycerin (NTG), either alone or in combination with uterotonics, may be of value to minimise the need for manual removal of the placenta in theatre under anaesthesia.

OBJECTIVES

To evaluate the benefits and harms of NTG as a tocolytic, either alone or in addition to uterotonics, in the management of retained placenta.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (14 January 2015), reference lists of retrieved studies and contacted experts in the field.

SELECTION CRITERIA

Any adequately randomised controlled trial (RCT) comparing the use of NTG, either alone or in combination with uterotonics, with no intervention or with other interventions in the management of retained placenta. All women having a vaginal delivery with a retained placenta, regardless of the management of the third stage of labour (expectant or active). We included all trials with haemodynamically stable women in whom the placenta was not delivered at least within 15 minutes after delivery of the baby.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.

MAIN RESULTS

We included three randomised controlled trials (RCTs) with 175 women. The three published RCTs compared NTG alone versus placebo. The detachment status of retained placenta was unknown in all three RCTs. Collectively, among the three included trials, two were judged to be at low risk of bias and the third trial was judged to be at high risk of bias for two domains: incomplete outcome data and selective reporting. The three trials reported seven out of 23 of the review's pre-specified outcomes.The primary outcome "manual removal of the placenta" was reported in all three studies. No differences were seen between NTG and placebo for manual removal of the placenta (average risk ratio (RR) 0.83, 95% confidence interval (CI) 0.47 to 1.46; women = 175; I² = 81%). A random-effects model was used because of evidence of substantial heterogeneity in the analysis. There were also no differences between groups for risk of severe postpartum haemorrhage (RR 0.93, 95% CI 0.62 to 1.39; women = 150; studies = two; I² = 0%). Blood transfusion was only reported in one study (40 women) and again there was no difference between groups (RR 1.00, 95% CI 0.07 to 14.90; women = 40; I² = 0%). Mean blood loss (mL) was reported in the three studies and no differences were observed (mean difference (MD) -115.31, 95% CI -306.25 to 75.63; women = 169; I² = 83%). Nitroglycerin administration was not associated with an increase in headaches (RR 1.09, 95% CI 0.80 to 1.47; women = 174; studies = three; I² = 0%). However, nitroglycerin administration was associated with a significant, though mild, decrease in systolic and diastolic blood pressure and a significant increase in pulse rate (MD -3.75, 95% CI -7.47 to -0.03) for systolic blood pressure, and (MD 6.00, 95% CI 3.07 to 8.93) for pulse rate (beats per minute) respectively (reported by only one study including 24 participants). Maternal mortality and addition of therapeutic uterotonics were not reported in any study.

AUTHORS' CONCLUSIONS

In cases of retained placenta, currently available data showed that the use of NTG alone did not reduce the need for manual removal of placenta. This intervention did not increase the incidence of severe postpartum haemorrhage nor the need for blood transfusion. Haemodynamically, NTG had a significant though mild effect on both pulse rate and blood pressure.

Clinical pharmacokinetics of nitrates

The pharmacokinetics of organic nitrates are discussed with emphasis on the possible clinical relevance. For glyceryl trinitrate, the measurement of plasma concentrations is very difficult. Its pharmacokinetics are unusual, with a very rapid disappearance from plasma, and large intraindividual and interindividual variations. After oral administration, there seems to be a very extensive first-pass hepatic extraction and the plasma concentrations are often below the detection limit; after sublingual administration, glyceryl trinitrate appears in plasma. With transdermal glyceryl trinitrate controlled-release systems, plasma concentrations of glyceryl trinitrate can be maintained over 24 hours, although with fluctuations and important intraindividual and interindividual variability. After administration of glyceryl trinitrate via different routes, glyceryl dinitrates and mononitrates are present in plasma. The pharmacokinetics of isosorbide dinitrate are somewhat easier to understand. The substance disappears less rapidly from the plasma than does glyceryl trinitrate. After oral administration, there is also a hepatic first-pass extraction; the plasma concentrations can be prolonged by administering slow-release products. Sublingual administration leads to higher plasma concentrations than oral administration. Isosorbide dinitrate is metabolized in the organism to isosorbide 5-mononitrate and isosorbide 2-mononitrate, which both have vasodilator activity: after administration of isosorbide dinitrate, the mononitrates, and mainly the 5-mononitrate, reach very high concentrations in plasma. Isosorbide 5-mononitrate has been studied in its own right as an antianginal agent: it is completely absorbed after oral administration; it has a half-life of around 4 hours, and oral standard and controlled-release formulations have been extensively studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous pharmacodynamic modeling of the non-steady-state effects of three oral doses of 1,3-glyceryl dinitrate upon blood pressure in healthy volunteers

The organic nitrate 1,3-glyceryl dinitrate (1,3-GDN) is one of the primary dinitrate metabolites of the antianginal agent nitroglycerin (GTN). Investigational New Drug Approval was sought to administer oral solution doses of 1,3-GDN to a small number (n = 3) of healthy volunteers; each subject receiving three doses at 1.2, 2.4, and 3.6 mg. With volunteers confined to a semirecumbent posture for the duration of each treatment (4-hr period postdose), diastolic blood pressure (DBP) was recorded and plasma samples collected for 1,3-GDN concentration analysis. Appreciable concentration-related decreases in DBP were observed, with maximal decreases from predose baseline values approximating 11 to 25 mm Hg. For each subject parametric pharmacodynamic modeling was performed with simultaneous analysis utilizing the DBP vs. time data from all three doses; an inhibitory Emax pharmacodynamic model was adopted. The temporal relationship between plasma 1,3-GDN concentrations and DBP displayed rapid equilibration. For subjects 1, 2 and 3, respectively, Emax was predicted as 12.9, 23.4, and 29.7 mm Hg, representing 21.5, 31.6, and 39.5% decreases in DBP from predose baseline values; plasma concentrations at half Emax (C50) were 2.75, 2.43, and 5.93 micrograms/L. Utilizing pharmacokinetic-pharmacodynamic modeling, 1,3-GDN plasma concentrations appear to relate to a systemic "effect measure" that is mechanistically representative of the therapeutic actions of organic nitrates as peripheral vasodilators. The establishment of a GDN plasma concentration-effect relationship together with the relatively high plasma levels of GDN achieved following GTN dosing supports the hypothesis that the GDNs contribute significantly to the hemodynamic effect observed with GTN.