The effect of acute ACE inhibition on atrial natriuretic peptide

1. The effect of acute angiotensin converting enzyme (ACE) inhibition on the plasma concentrations of atrial natriuretic peptide (ANP) was investigated in a single-blind placebo controlled crossover study in healthy volunteers. 2. Intravenous infusion of 2 mg cilazaprilat resulted in a significant and short lasting inhibition of ACE as evidenced by a decrease of plasma angiotensin II and an increase in plasma renin activity. 3. When compared with placebo cilazaprilat lowered diastolic pressure and increased heart rate significantly. 4. No effect of cilazaprilat was found on plasma ANP levels, suggesting that angiotensin II does not mediate ANP release.

The pharmacokinetics and angiotensin converting enzyme inhibition dynamics of cilazapril in essential hypertension

1. In a double-blind, placebo controlled, crossover study 12 patients with essential hypertension received single doses of 5, 10 and 20 mg of cilazapril. 2. Peak plasma levels of cilazaprilat and the 24 h areas under curve were directly proportional to dose. 3. The elimination half-life during the first 8 h was about 1.7 h. 4. From 24 h onwards there was a prolonged terminal elimination phase with a half-life of about 40 h, and strict dose proportionality of plasma concentrations was not maintained. 5. The pharmacokinetics of cilazaprilat and the pharmacodynamics of plasma ACE inhibition were well described by a one compartment model with saturable binding to ACE. 6. The coefficients of the model which related to plasma ACE and its interaction with cilazaprilat were in good agreement with model independent observations. 7. The values for kinetic and dynamic parameters in hypertensive patients were comparable with those reported for healthy volunteers.

Antihypertensive effects and pharmacokinetics of single and consecutive doses of cilazapril in hypertensive patients with normal or impaired renal function

1. A 1.25 mg dose of cilazapril, a new angiotensin-converting enzyme (ACE) inhibitor, was administered orally to two groups of hypertensive patients, five with normal renal function (NRF) and seven with impaired renal function (IRF), once daily for 5 or 8 consecutive days. Blood pressure, heart rate and serum ACE activity were measured up to 24 h following the initial and the last dose. Plasma level profiles of cilazapril and its active diacid were also evaluated on the first and the last day of treatment. 2. Cilazapril induced significant falls in both systolic and diastolic blood pressures without increasing heart rate. The antihypertensive effect was evident within 1 h after drug administration and was sustained for up to 24 h, particularly after consecutive dosing. 3. Serum ACE activity was markedly suppressed over 24 h. The recovery of ACE activity was delayed in the IRF group when compared with the NRF group. 4. Plasma concentrations of the active diacid in the IRF group were higher than in the NRF group with significant differences in the peak concentrations and area under the plasma concentration-time curve (AUC). The plasma concentration profile for the parent drug was similar for both the NRF and IRF groups. 5. A significant inverse correlation was found between the creatinine clearance and the AUC for the diacid. 6. Cilazapril is a potent ACE inhibitor with a prolonged duration of antihypertensive effect and is a useful agent for controlling blood pressure in hypertensives either with NRF or IRF. In patients with severe renal impairment the dose of cilazapril should be reduced.

The metabolism and disposition of 14C-indolidan, a potent and orally active cardiotonic agent, in four species of laboratory animals

1. The metabolism and disposition of 14C-indolidan, a potent, orally-active positive inotrope with vasodilator properties, has been studied after single dose oral administration to rats, mice, dogs and monkeys. 2. Excretion of 14C in all 4 species was mostly via the urine, largely as parent drug together with two other major metabolites. 3. The two metabolites have been isolated and identified, by mass spectroscopy and 1H-n.m.r., as a dehydro-compound, with a double bond in the pyridazanone ring, and a hydroxylated derivative of the parent drug. 4. Plasma t 1/2 values, based on 14C, were 14 h in dog, 5 h in mouse and 8 h in monkey. Plasma t 1/2 of parent drug, by h.p.l.c. was 10 h in dog, approx. 5 h in rodents, and 8 h in monkeys. 5. Tissue distribution in rats showed no accumulation in any tissue; 14C concn. in all tissues were indistinguishable from background 48 h after dosage. 14C peaked at 6-8 h for most tissues but in blood and plasma, 14C was maximal 1 h after dosing.

Pharmacokinetics of cadralazine in hypertensive patients

Pharmacokinetics of cadralazine, urinary recovery of its putative active metabolite 3-hydrazino-6-aminopiridazine derivative (ISF 2405) and clinical effects were assessed in a placebo-controlled trial in 8 hypertensive in-patients, after acute oral administration of cadralazine. After a 2-week placebo-washout period, the protocol envisaged two consecutive days of monitoring of blood pressure and heart rate. On the first day a placebo tablet was given (9 am), while on the second day patients received a 30 mg cadralazine tablet in single-blind conditions. Blood and urine samples were obtained during the active drug day until 12 h after administration. Concentration of cadralazine in plasma and urine was detected by a specific HPLC method, while the metabolite ISF 2405 was detected in urine by a GC-MS method. Cadralazine caused gradual and long-lasting pressure decrease, statistically significant in comparison to placebo between 3 and 12 hours from drug intake, accompanied by a significant increase in heart rate. Cadralazine by oral route was promptly absorbed with a mean peak time of 1.3 h. Thereafter it followed a monoexponential decay curve, with a plasma half life of 3.1 h. The relative different bioavailability of oral cadralazine among patients was not correlated with cardiovascular changes. Urine recovery of unchanged drug after 12 h was high, reaching 67.3%, while concentration of metabolite ISF 2405 was about 1/1000 of parent compound.

Liquid chromatographic determination of indolidan and its dehydro metabolite in plasma. Use of the Varian AASP for solid-phase extraction

A method is described for the determination of indolidan and its dehydro metabolite in human plasma. Two procedures are given, one manual and one which is semi-automated by use of the Varian AASP (Automated Analytical Sample Processor). The method involves solid-phase extraction to isolate the drug, metabolite, and an internal standard from plasma. The manual procedure requires elution of the analytes from the extraction column with methanol, evaporation of the methanol to dryness, and reconstitution in mobile phase prior to injection into a reversed-phase liquid chromatographic system. Using the AASP (semi-automated procedure), the analytes are eluted from the extraction column directly into the chromatographic system, resulting in substantial savings in sample preparation time. The limit of detection for both drug and metabolite is 0.25 ng/ml in plasma. Detection was made by ultraviolet absorbance, using wavelength programming to optimize the sensitivity of the assay for each compound.

Disposition and metabolism of [14C]-amezinium metilsulfate in rats

Disposition and metabolism of [14C]-amezinium metilsulfate (4-amino-6-methoxy-1-phenylpyridazinium methylsulfate, Risumic) were systematically studied in rats after intravenous (5 mg/kg) or oral (20, 100 mg/kg) administration. After oral administration at 20 mg/kg, blood level reached the maximum (Cmax) of 0.65 microgram eq/ml at 3 h (tmax) and decreased with t1/2 of 8.1 h. Levels in plasma and most tissues elevated to the Cmax at 3 h. The liver level was the highest (61 times as high as plasma level) of all examined tissues. Most tissue levels decreased thereafter essentially in parallel with plasma levels. The findings by whole-body autoradiography essentially agreed with those by radiometry. In lactating rats, milk levels were virtually similar to plasma levels. [14C]-Amezinium metilsulfate radioactivity in fetus and fetal blood was around 0.3 microgram eq/g, being about 1/10 level of maternal plasma level. About 24, 72 and 42% were excreted in urine, feces and bile, respectively. Re-absorption of biliary metabolites accounted for about 31%, being about 13% of orally given [14C]-amezinium metilsulfate. Plasma and aorta contained unchanged amezinium and glucuronide of hydroxyl amezinium MIII. In the brain, the major metabolite was O-demethyl amezinium MV and unchanged drug was not detected. Urinary metabolites were largely MIII glucuronide and the unchanged drug. Biliary metabolite was found composed mostly from MIII glucuronide. In feces, MIII and the unchanged amezinium were found. MIII and its glucuronide were novel metabolites which were identified by thin-layer chromatography and mass spectrometry.

Pharmacokinetics of single and consecutive doses of cilazapril and its depressor effects in hypertensive patients with renal dysfunction

The pharmacokinetic properties and antihypertensive effects of cilazapril, a long-acting converting enzyme inhibitor, were investigated in seven hypertensive patients with renal failure. Cilazapril 1.25 mg was given orally once a day for 5 or 8 days. Cilazapril induced a significant decrease in both systolic and diastolic blood pressures, and its antihypertensive effect was still present 24 hours after administration. Serum-converting enzyme activity was markedly suppressed for at least 24 hours. No significant differences were noted in plasma peak level and the area under the curve between the first and last days of treatment. These results suggest that cilazapril has a long-lasting effect and is a useful antihypertensive agent in controlling blood pressure in hypertensive patients with renal failure.

Pimobendane (UD-CG 115 BS) in the treatment of severe congestive heart failure. An acute haemodynamic cross-over and double-blind study with two different doses

1. We compared the effects of two doses (5 and 10 mg) of oral pimobendane (UD-CG 115) on haemodynamics in eight patients suffering from chronic congestive heart failure. The two doses were given according to a randomized cross-over double-blind protocol; haemodynamics and plasma levels of pimobendane and its main metabolite UD-CG 212, were determined 1, 2, 3, 5, 7, 9, 11 and 12 h after each dose. 2. Both doses significantly improved the left and right ventricular functions of these patients, with a peak action 3 h after drug intake and long duration (more than 12 h). A significant dose-effect relationship was observed only for pulmonary wedge pressure and right atrial pressure. Significant correlations were found between UD-CG 212 plasma levels and cardiac index (r = 0.54, P less than 0.05), and pulmonary wedge pressure (r = 0.74, P less than 0.001); no correlation was found between these haemodynamic variables and pimobendane plasma levels. 3. One patient developed a transient drop in blood platelets together with a cutaneous rash, while three others had a transient and mild decrease of thrombocytes. 4. In conclusion, pimobendane improved right and left ventricular functions in severe heart failure. Both doses (5 and 10 mg) were effective. The higher dose induced marked improvement of the haemodynamic variables but the difference between doses was only significant for right atrial and pulmonary wedge pressures.

Pharmacokinetics of an active cadralazine metabolite in plasma and blood vessels of spontaneously hypertensive rats

The plasma and blood vessel (aorta and mesenteric artery) levels of (+/-)-6-[ethyl(2-hydroxypropyl)amino]-3-hydrazinopyridazine (ISF-2405), an active metabolite of cadralazine, were determined and compared with the changes in blood pressure in spontaneously hypertensive rats after single oral administration of cadralazine. The mean plasma level of ISF-2405 reached a maximum at 0.5 h after oral administration of 3 mg/kg of cadralazine, followed by a rapid elimination with a half-life of 1.0 h, whereas the mean aorta level of ISF-2405 reached a maximum at 4 h after dosing, followed by a slow elimination with a half-life of 6.5 h. The mean mesenteric artery levels of ISF-2405 were almost the same as the mean aorta levels over the time investigated. Both patterns of aorta and mesenteric artery levels of ISF-2405 were in good agreement with those of the hypotensive effects. These findings substantiate the assumption that the slow onset and long duration of the pharmacological effect of cadralazine is closely related to the distribution pattern of the active metabolite ISF-2405 in blood vessels, a target tissue of antihypertensive vasodilator drugs.

Antihypertensive effects and pharmacokinetics of single and consecutive doses of cilazapril in hypertensive patients with normal and impaired renal function

The antihypertensive effects and pharmacokinetic properties of cilazapril, a long-acting angiotensin-converting enzyme (ACE) inhibitor, were investigated in hypertensive patients with normal renal function (NRF; n = 5) and those with impaired renal function (IRF; n = 7). A 1.25-mg dose of cilazapril was administered orally once a day for 5 or 8 days. Measurement of blood pressure and sampling of blood specimens were done on the first and last days of treatment. Cilazapril induced significant falls in systolic and diastolic blood pressures as early as 1 h after administration. The antihypertensive effects were still present at 24 h postdose. Serum ACE activity was markedly suppressed over 24 h, with the enzyme inhibition greater in the IRF group. Plasma levels of the active diacid in the IRF group were higher than those in the NRF group, with significant differences in the peak levels and areas under the curve (AUC). A significant inverse correlation was found between the creatinine clearance and the AUC for the diacid. Cilazapril was well tolerated by all the patients, and no adverse reactions were observed. These results suggest that cilazapril has a long-lasting action and that it is a useful antihypertensive agent for controlling blood pressure in patients with either NRF or IRF.

High-performance liquid chromatographic determination of cadralazine in human plasma and urine

A sensitive and selective high-performance liquid chromatographic method for determination of intact cadralazine in human plasma or urine has been developed. The sample was buffered (plasma, pH 7.6; urine, pH 12.0) and mixed with internal standard before it was applied to an Extrelut-3 column. After adsorption, the column was eluted with chloroform, and the eluate was extracted with sodium acetate-hydrochloric acid buffer (pH 2.1). A 20-microliters aliquot of the aqueous phase was chromatographed on a 5-microns Spherisorb ODS reversed-phase column, with acetonitrile-phosphate buffer (pH 6.0, 25:75) as eluent. The quantitation was achieved by monitoring the ultraviolet absorbance at 254 nm. The detection limit was 0.03 nmol/ml in plasma and 5.00 nmol/ml in urine. The within-assay variation and the day-to-day reproducibility were less than or equal to 10% for plasma or urine standard samples. No interferences from possible metabolites or endogenous constituents could be noted. The utility of the method was demonstrated by analysing cadralazine in samples from one hypertensive subject on a therapeutic dose of the drug (7.5 mg orally).

Pharmacokinetics of cinoxacin in elderly patients following repeated oral administration

Cinoxacin is an antibacterial drug belonging to the quinolone class used in the treatment of urinary tract infections due to common gram-negative pathogens. Considering the high frequency of urinary tract infections in elderly people where aging represents a physiopathological condition frequently requiring an adjustment of the dosage regimen, the pharmacokinetic behaviour of cinoxacin (500 mg/12 h) in aged patients was investigated to find out if age-dependent differences may be established. The main differences detected were a shift to 4 h of the Tmax and a partly reduced clearance in comparison with data referred to younger people. On the other hand the findings showed that no accumulation occurred. High urinary concentrations of cinoxacin, exceeding the MICs for most urinary tract pathogens were found up to the 12th hour after administration.