Cicletanine

Antihypertensive drugs from the thiazide diuretic drug class have been shown to reduce mortality and cardiovascular morbidity. Loop diuretics are indicated and used as antihypertensive drugs but a systematic review of their blood pressure lowering efficacy or effectiveness in terms of reducing cardiovascular mortality or morbidity from randomized controlled trial evidence has not been conducted.

To determine the dose related decrease in systolic and/or diastolic blood pressure as well as adverse events leading to patient withdrawal and adverse biochemical effects (serum potassium, uric acid, creatinine, glucose and lipids profile) due to loop diuretics versus placebo control in the treatment of patients with primary hypertension.

Medline (1946-February 2012), EMBASE (1974-February 2012), CENTRAL (issue 2, 2012) and bibliographic citations were searched.

Double blind randomized placebo controlled trials of at least 3 weeks duration comparing loop diuretic with a placebo in patients with primary hypertension defined as BP >140/90 mmHg at baseline were included.

Two authors independently assessed the risk of bias and extracted data. Weighted mean difference and a fixed effects model were used to combine continuous outcome data. The drop outs due to adverse effects was analysed using relative risk ratio.

Nine trials evaluated the dose-related blood pressure lowering efficacy of five drugs within the loop diuretics class (furosemide 40 to 60mg, cicletanine 100 to 150 mg, piretanide 3 to 6 mg, indacrinone enantiomer -2.5 to -10.0/+80 mg and etozolin 200 mg) in 460 patients with baseline blood pressure of 162/103 mmHg for a mean duration of 8.8 weeks. The best estimate of systolic/diastolic blood pressure lowering efficacy of loop diuretics was -7.9 (-10.5, -5.4) mmHg/ -4.4 (-5.6, -2.8) mmHg . Withdrawals due to adverse effects and serum biochemical changes did not show a significant difference.The 2012 updated search resulted in no additional new trials meeting the minimum inclusion criteria.

Based on the limited number of published RCTs, the systolic/diastolic blood pressure lowering effect of loop diuretics is modest (-8/-4 mmHg) and is likely an overestimate due to the high risk of bias in the included studies. There are no clinically meaningful BP lowering differences between different drugs within the loop diuretic class. The dose ranging effects of loop diuretics could not be evaluated. The review did not provide a good estimate of the incidence of harms associated with loop diuretics because of the short duration of the trials and the lack of reporting of adverse effects in many of the trials.

High-fat diet and consequent metabolic syndrome (MS) can lead to elevated risk for cardiac arrhythmias. This preclinical study was to investigate if cicletanine (CIC) could produce cardioprotective effects in conscious rabbits exhibiting the main symptoms of MS.

NZW rabbits that had undergone an 8-week-long cholesterol-enriched diet (1.5%) were instrumented with a pacemaker electrode and randomly assigned into 3 groups according to the oral treatment of either CIC (50 mg·kg) or sotalol (25 mg·kg) and their placebo b.i.d. over 5 days. Study groups were subjected to either "arrhythmia challenge" by programmed electrical stimulation in the "Arrhythmogenesis" study (N = 54) or global myocardial ischemia by rapid pacing in the "Ventricular Overdrive Pacing-induced Myocardial Ischemia" study (N = 18). The antiarrhythmic effect was evaluated by the establishment of the incidence of programmed electrical stimulation-induced arrhythmias. Proarrhythmia indicators (eg, QTc, Tpeak-Tend) were also measured to assess the cardiac safety profile of CIC. To evaluate the background of antiarrhythmic effect, cardiac cyclic nucleotide (cyclic 3',5'-guanosine monophosphate [cGMP], cyclic 3',5'-adenosine monophosphate [cAMP]) and nitric oxide content were determined. The antiischemic effect was characterized by change of intracavital ST segment.

Cicletanine treatment significantly decreased the incidence of ventricular arrhythmias, increased cardiac cGMP and nitric oxide content and reduced cardiac cAMP level. Cicletanine did not modify significantly QTc and Tpeak-Tend interval. The ST-segment change in response to rapid pacing was reduced significantly by CIC. (P < 0.05).

Cicletanine exerts beneficial cardiac effects in rabbits with symptoms of MS, which may be of influence with regard to the clinical application of the drug.