Adenosine antagonists for prevention of contrast-induced nephropathy: A meta-analysis of randomized controlled trials with trial sequential analysis

Contrast-induced nephropathy (CIN) is caused by intravascular administration of contrast agent. The efficacy of adenosine antagonists (AAs) in preventing CIN remains controversial, and its elucidation was the objective of the present meta-analysis. A trial sequential analysis (TSA) to assess the reliability of the pooled results was also performed. The Medline, Embase, Web of Science and Cochrane databases were searched to retrieve all published randomized controlled trials (RCTs) comparing AAs with controls in preventing CIN. Heterogeneity, publication bias and quality of studies were assessed. Sensitivity, cumulative and subgroup analyses were also performed. The risk of random errors was evaluated by TSA. A total of 17 trials with 1,483 subjects were included. Pooled results indicated that AAs significantly reduced the incidence of CIN [risk ratio, 0.53; 95% confidence interval (CI), 0.29-0.95; P=0.034] and the serum creatinine (SCr) level after contrast media (CM) administration (standardized mean difference, -0.24; 95% CI, -0.44 to -0.04; P=0.019). Meta-regression did not identify any significant source of heterogeneity. In the subgroup analyses, AAs tended to exhibit a greater prevention efficacy in trials with sample sizes of ≥70, baseline SCr of <1.5 mg/dl and low study quality. TSA on the incidence of CIN indicated that the required information size determined as n=1,778 was not reached, and that the cumulative Z-curve did not cross the TSA boundary. In conclusion, the present meta-analysis of data from current RCTs suggested that AAs reduce the incidence of CIN and the SCr levels after CM administration. However, TSA showed that the risk of having a false-positive result was greater than 5% in the meta-analysis of the incidence of CIN, indicating that more evidence is required to ensure the benefit of AAs in preventing CIN.

Theophylline and aminophylline for prevention of acute kidney injury in neonates and children: a systematic review

OBJECTIVE

To compare the efficacy and safety of theophylline or aminophylline for prevention of acute kidney injury (AKI) in neonates and children.

DESIGN

Systematic review and meta-analysis with application of Grading of Recommendations, Assessment, Development and Evaluation system.

DATA SOURCES

PubMed/MEDLINE, Embase, Google Scholar and Cochrane renal group were searched from 1970 to May 2018.

ELIGIBILITY CRITERIA

Randomised clinical trials and quasi-randomised trials comparing the efficacy and safety of prophylactic theophylline or aminophylline for prevention of AKI in neonates and children were included. The primary outcomes were: incidence of AKI, serum creatinine levels and all-cause mortality.

RESULTS

A total of nine trials were included in the qualitative synthesis. Six trials including 436 term neonates with birth asphyxia who received a single dose of theophylline were finally included in the meta-analysis. The pooled estimate showed 60% reduction in the incidence of AKI in neonates with severe birth asphyxia (RR: 0.40; 95% CI 0.3 to 0.54; heterogeneity: I²=0%) (moderate quality evidence), decrease in serum creatinine over days 2-5 (very low to low quality evidence) without significant difference in all-cause mortality (RR: 0.88; 95% CI 0.52 to 1.50; heterogeneity: I²=0%) (very low-quality evidence). A significant difference in the negative fluid balance, increase in GFR and decrease in urinary β2 microglobulin was seen in favour of theophylline.

CONCLUSION AND RELEVANCE

A single dose of prophylactic theophylline helps in prevention of AKI/severe renal dysfunction in term neonates with severe birth asphyxia (moderate quality evidence) without increasing the risk of complications and without affecting all-cause mortality (very low-quality evidence).

TRIAL REGISTRATION NUMBER

CRD 42017073600.

Effectiveness and tolerability of istradefylline for the treatment of restless legs syndrome: an exploratory study in five female patients

BACKGROUND

Studies of istradefylline (KW6002), an adenosine A2A-receptor antagonist, have provided evidence of its efficacy as a nondopaminergic antiparkinsonian drug. Antiparkinsonian drugs have also had efficacy in treating restless legs syndrome (RLS).

OBJECTIVES

The aims of this study were to assess the effectiveness and tolerability of istradefylline in the treatment of RLS.

METHODS

This was a single-center, multiparametric, prospective trial of istradefylline as a treatment for moderate to severe idiopathic RLS. It was conducted at the Shands/Jacksonville Sleep Disorders Center, University of Florida, Jacksonville, Florida, from March 2003 to October 2003. Patients received a single PO 80-mg dose QD of istradefylline in the late afternoon or early evening for 6 weeks. Appropriate tolerability evaluations (ie, vital assessments, physical examination, clinical laboratory tests, and electrocardiogram) were performed at screening, while on study drug, and after withdrawal of study drug.

RESULTS

Fifteen participants (mean [SD] age, 61 [7.1] years; range, 50-69 years) were screened for enrollment. The mean duration of RLS was 18 years. Of the 15 potential patients, 6 did not meet entry criteria, 2 withdrew consent, 1 had not completed baseline procedures at the time of study suspension, and 1 was excluded for administrative reasons. Therefore, a total of 5 patients received the study drug. Of these, 3 (60%) patients responded favorably to istradefylline treatment. Improvement in the periodic limb movement index was observed in 3 patients compared with baseline (patients 2, 4, and 5 [index score: 6, 4, 9 vs 50, 35, 18, respectively]). Improvement in the International RLS Rating Scale scores was observed in 3 patients compared with baseline (patients 2, 4, and 5 [index score: 7, 23, 9 vs 35, 25, 20, respectively]). There was a return to baseline severity in 2 of the 3 patients after withdrawal of study drug. Improvement in RLS symptoms was observed in 3 patients treated with istradefylline for 6 weeks. A clinical worsening of baseline insomnia was observed in 2 patients.

CONCLUSIONS

Although we could not definitively conclude a beneficial effect based on this small exploratory trial, we found the data to be encouraging. The study drug was well tolerated. Further study of this compound in the treatment of RLS is justified.

Characterization and tissue location of the neural adenosine receptor in the rat ileum

1. The aim of the present investigation was to characterize and determine the tissue location of the adenosine receptors present in the rat ileum using a method that detects drug action on the cholinergic nerves innervating the longitudinal and circular muscles. 2. The non-selective adenosine agonist, NECA (10 and 100 nM) caused significant concentration-related reductions in the circular muscle responses to transmural stimulation over the frequency range of 2.5-40 Hz, but did not affect the responses of the longitudinal muscle, nor did it reduce the muscle responses of the guinea-pig ileum. 3. The affinity order of antagonists at inhibiting the effect of NECA on the circular muscle was: CPDPX>8-PT>DMPX with apparent pA2 values of 9.31, 7.54 and 5.63 respectively. CPDPX (10-100 nM) caused parallel displacements of the concentration-effect curves to CPA with a pKb value of 9.15 and Schild slope of 1.03. 4. The agonists previously tested in the rat jejunum peristaltic reflex preparation were also shown to inhibit responses of the rat ileum in the following decreasing order of potency: CPA>NECA>2-CADO>R-PIA>S-PIA>>PAA. In addition, CHA and CCPA were also potent agonists. NECA (100 nM) and CPA (32 nM) did not inhibit carbachol (1 microM)-induced tone of tissues pre-treated with TTX (1 microM). 5. In conclusion, the rat ileum contains inhibitory A1 adenosine receptors situated on cholinergic nerve endings innervating the circular muscle.

Adenosine release mediates cyanide-induced suppression of CA1 neuronal activity

The rapid suppression of CNS function produced by cyanide (CN) was studied by field, intracellular, and whole-cell recording in hippocampal slices (at 33-34 degrees C). Population spikes and field EPSPs were depressed by 4-5 min bath applications of 50-100 microM CN (IC50 was 18 miroM for spikes and 72 microM for EPSPs). The actions of CN were reversibly suppressed by the adenosine antagonists 8-sulfophenyltheophylline (8-SPT; 10 microM) and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.2 microM), potentiated by the adenosine transport inhibitor dipyridamole (0.5 microM), but unaffected by the KATP channel blocker glyburide (10 microM). Therefore the CN-induced reductions of synaptic efficacy and postsynaptic excitability-demonstrated by synaptic input:output plots-are mediated mainly by adenosine. In whole-cell or intracellular recordings, CN depressed EPSCs and elicited an increase in input conductance and an outward current, the reversal potential of which was approximately -90 mV (indicating that K+ was the major carrier). These effects also were attenuated by 8-SPT. In the presence of 1 mM Ba, CN had no significant postsynaptic action; Cs (2 mM) also prevented CN-induced outward currents but only partly blocked the increase in conductance. Another 8-SPT-sensitive action of CN was to depress hyperpolarization-activated slow inward relaxations (Q current). At room temperature (22-24 degrees C), although it did not change holding current and slow inward relaxations, CN raised the input conductance; this effect also was prevented by 8-SPT (10 microM), but not by glyburide (10 microM). Adenosine release thus appears to be the major link between acute CN poisoning and early depression of CNS synaptic function.

Evidence of spare A1-adenosine receptors in guinea pig atrioventricular node

In normoxic, isolated perfused guinea pig hearts instrumented for measurement of atrioventricular nodal conduction time (AVCT), an analysis utilizing the irreversible A1-adenosine (Ado) antagonist, meta-1,3-phenylene diisothiocyanate xanthine amine cogener (m-DITC-XAC), a novel isothiocyanate derivative of 1,3-dialkylxanthine, was used to investigate whether spare A1-Ado receptors exist in the guinea pig atrioventricular (AV) node and the degree of amplification (reserve) between A1-Ado receptor occupancy and dromotropic response (e.g., AVCT slowing). The potency, dose dependency, and kinetic profile (time dependence of washout and washin) of m-DITC-XAC was determined and compared with those of known competitive (reversible) A1-Ado receptor antagonists. In the presence of m-DITC-XAC, Ado and N6-cyclopentyladenosine (CPA) produced submaximal dromotropic responses. In a series of 19 hearts, m-DITC-XAC caused 100% apparent antagonism of the effect of Ado on AVCT even after 60 min of washout. In contrast, greater than 90% of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and XAC-induced antagonism of the effect of Ado on AVCT dissipated within 35 min. Unlike XAC, which caused maximal attenuation of Ado's AVCT effect within 5 min and remained constant thereafter, m-DITC-XAC showed marked time- and concentration-dependent behavior. It was found that 5 min of 0.5 microM m-DITC-XAC pretreatment irreversibly inactivated 72% of the A1-Ado receptors mediating the dromotropic effect, and the estimated agonist equilibrium dissociation constant for CPA was 84 +/- 4 nM. The percent of spare A1-Ado receptors at the EC50 and extrapolated maximal S-H interval prolongation levels was 20 and 54%, respectively, and the reserve (coupling amplification) varied from 1 to 2.3 within the 0-50% maximal response range. In summary, m-DITC-XAC appears to specifically and irreversibly antagonize the negative dromotropic effect of Ado and CPA, and guinea pig AV nodal tissue possesses spare A1-Ado receptors.