Monitoring of proteinuria in phase I studies in healthy male subjects.

OBJECTIVE: The quantitative measurement of urinary marker proteins may improve the sensitivity of monitoring renal function in healthy male subjects in phase I studies. Little is known about the variability of physiological proteinuria in young, healthy male subjects. Thus, the biological and analytical variability of three marker proteins, i.e. albumin, alpha(1)-microglobulin and N-acetyl-beta-D-glucosaminidase (NAG), were investigated in this population. METHODS: Seven young, healthy male subjects participated in a prospective two-way cross-over study, and 139 in a retrospective study. Albumin and alpha(1)-microglobulin were determined by immunological methods (radial immunodiffusion and/or kinetic nephelometry), and NAG by enzyme activity in a colorimetric assay. RESULTS: The inter-assay precision of NAG, albumin and alpha(1)-microglobulin is good (< 15%) if automated kinetic nephelometry is applied for albumin and alpha(1)-microglobulin determination, but less impressive (< 25%) with radial immunodiffusion. The highest frequency of detectable proteinuria and highest creatinine-adjusted protein levels are found in the second morning urine voided after a night's rest. The intra-individual biological variability of NAG excretion from day to day is low (CV: 15-25%), irrespective of outpatient or inpatient settings. By contrast, albumin and alpha(1)-microglobulin excretion can differ by a factor of 2-3 from day to day, and higher levels are predominantly found in outpatient settings. The reference ranges for young, healthy male subjects are generally lower than published in cross-sectional studies in the total healthy population. CONCLUSION: These findings and established reference ranges for young, healthy male subjects may assist in the evaluation of proteinuria in clinical pharmacological phase I trials.

Absolute and relative bioavailability of the HMG-CoA reductase inhibitor cerivastatin.

To determine the absolute bioavailability of the HMG-CoA reductase inhibitor cerivastatin, 12 healthy young male volunteers received single doses of either 100 micrograms as a 1-minute bolus infusion or 200 micrograms orally as tablets in a controlled, randomized crossover study. In addition, 8 of the 12 subjects participated in a third treatment period in which 200 micrograms cerivastatin were administered as an oral solution as reference for determining the relative bioavailability of the tablet drug formulation. Plasma samples were analyzed for cerivastatin by a specific HPLC assay with fluorescence detection after post-column irradiation of the eluate, with a limit of quantification of 0.1 microgram/l. Following all treatments, cerivastatin was well tolerated and no clinically relevant adverse events or changes in laboratory parameters were observed. Vital signs and ECG remained unchanged. Plasma concentration/time profiles of cerivastatin following intravenous bolus could be described by a 2-compartment model with a distribution half-life of 3-5 min and an elimination half-life of 1.5-2.4 h. For the 2 oral administrations a 1-compartmental pharmacokinetic model with a first-order absorption process was best to describe the plasma concentration/time data. Based on the AUCnorm values of the 7 subjects, valid for complete pharmacokinetic evaluation, the absolute bioavailability of tablet and oral solution was 60.0 and 59.6% (90% confidence intervals 53-68%), respectively. The relative bioavailability of tablet compared with solution was 100.7% (90% confidence interval 89-114%), with tablet and oral solution showing nearly identical in vivo absorption characteristics and almost superimposable plasma concentration/time curves. The tablet formulation, therefore, can be regarded as an optimal oral formulation with respect to galenic aspects.

Influence of the H2-receptor antagonists cimetidine and ranitidine on the pharmacokinetics of nimodipine in healthy volunteers.

A possible interaction between the calcium antagonist nimodipine and the H2-receptor antagonists cimetidine and ranitidine has been investigated in two separate studies in healthy subjects. In eight young volunteers the concomitant administration of nimodipine 30 mg t.i.d. and cimetidine 1000 mg/d for 7 days led to a significant increase of the relative bioavailability of nimodipine. The changes in the pharmacokinetic parameters were not accompanied by discernible haemodynamic effects or any change in the tolerability of nimodipine. There was no evidence of any significant change in the steady-state pharmacokinetics of nimodipine during five days of combined treatment with 30 mg t.i.d. nimodipine and ranitidine 300 mg/d given as single morning dose to twelve healthy, elderly subjects. Analysis of haemodynamics, clinical chemistry and tolerance also did not reveal any difference between the two treatment periods.

Neuroendocrine effects of ipsapirone on the hypothalamic-pituitary adrenal axis: CRF, ACTH and cortisol in healthy volunteers.

The neuroendocrine effects (changes in plasma CRF, ACTH and cortisol) of single and multiple (t.d.s. for 2 days) doses of ipsapirone (BAY Q 7821) 5 and 10 mg have been investigated in 6 healthy male volunteers. The study followed a balanced complete block, placebo-controlled and double blind design with two baseline phases (pre and post-treatment). Volunteers were investigated on identical days during 5 successive weeks. The results do not show a specific effect of ipsapirone on the hypothalamic-pituitary-adrenal axis when doses in the range of 5-30 mg per day were given.

Effects of rioprostil on the postprandial glucose, GIP, insulin and gastrin levels in volunteers.

The study is of double-blind crossover design. In the first part of the study, rioprostil (300 micrograms and 600 micrograms) is given orally with a solid breakfast to 9 healthy male volunteers. Both doses of rioprostil delay and reduce the 3-h postprandial GIP release. They also reduce the maximal postprandial insulin concentration, but only rioprostil (600 micrograms) reduces the 3-h integrated release of insulin significantly (by approximately 20%). Neither dose modifies the postprandial glucose gastrin levels significantly. In another study two groups of 6 volunteers are studied in parallel; they are given either rioprostil (600 micrograms) or a placebo each evening for 14 days. On the mornings before and on days 13 and 14 of the study the volunteers take a solid breakfast and blood glucose is measured 1 h and 2 h postprandially. The results show that no differences in the basal and postprandial glucose levels are observed. In conclusion, rioprostil given with a meal can reduce the insulin release but it does not change the postprandial blood glucose levels when given as a single dose or repeatedly in an evening dose. This study shows that rioprostil can be given to patients with diabetes.

Effect of rioprostil, a methyl-prostaglandin E1, on plasma level and renal excretion of beta-acetyldigoxin.

A single oral dose of rioprostil, a synthetic methyl-prostaglandin E1, together with or 2 h before ingestion of 0.8 mg beta-acetyldigoxin significantly delays the rate but does not change the extent of beta-acetyldigoxin absorption. However, repeated evening doses of rioprostil do not alter either the glycoside steady-state plasma levels or renal excretion.

Increase in plasma atrial natriuretic factor and right atrial area during endogenous and exogenous volume loading in healthy volunteers: effect on plasma renin activity, aldosterone and antidiuretic hormone.

The mechanisms of atrial natriuretic factor (ANF) release and the effects of ANF on plasma renin activity (PRA), plasma aldosterone and plasma antidiuretic hormone were investigated in two groups of normal subjects. One group was studied before and after endogenous volume loading produced by 30 min of head-down tilt. The other group was studied before and after an exogenous volume load in the form of 1 litre of isotonic saline infused over 30 min. Measurements made included right atrial area by two-dimensional echocardiography, PRA, plasma aldosterone, plasma antidiuretic hormone and plasma levels of ANF. There was a significant correlation between the increase in atrial area and plasma ANF concentrations after endogenous and exogenous volume loading. Levels of PRA and plasma aldosterone were suppressed significantly after exogenous volume loading but not after endogenous volume loading. The concentration of plasma antidiuretic hormone was not affected by either procedure. Short-term changes in right atrial pressure appear to regulate the plasma levels of ANF in normal people.

Plasma concentration-response relationships for some cardiovascular effects of dihydropyridines in healthy subjects.

The pharmacokinetics and some hemodynamic effects of three dihydropyridine (DHP) calcium channel blockers were studied in healthy subjects. In a randomized order, each subject was given 24 micrograms/kg nifedipine, 40 micrograms/kg nitrendipine, or 10 micrograms/kg nisoldipine intravenously. The three DHPs differed as to their total clearance and volume of distribution (nifedipine less than nisoldipine less than nitrendipine) but showed similar values for elimination half-lives. All three drugs evoked increases in heart rate and forearm blood flow (FBF) and small decreases in blood pressure. Whereas the observed peak changes in heart rate were virtually identical for the three drugs (about 45% above baseline), the peak changes in FBF were more pronounced in response to nitrendipine and nisoldipine (greater than 200% above baseline) than in response to nifedipine (79% above baseline). The heart rate and FBF responses to the DHPs were related directly to the drug concentrations in plasma. The plasma level-response curves obeyed Hill's equation. They showed that the DHPs differ mainly in their potencies at dilating the forearm resistance vessels (nifedipine less than nitrendipine less than nisoldipine).

Bactericidal activity of ciprofloxacin, norfloxacin and ofloxacin in serum and urine after oral administration to healthy volunteers.

A 200 mg oral dose of ciprofloxacin, norfloxacin or ofloxacin was administered to six healthy male volunteers in a three way cross-over study in order to examine the kinetics in humans in relation to the bactericidal activity in serum and urine. Serum concentrations for ciprofloxacin were similar to norfloxacin and lower than ofloxacin. Despite this fact, ciprofloxacin showed the highest serum bactericidal titers compared to norfloxacin and ofloxacin when serum-resistant Escherichia coli C14 was used as a test organism. These results correlate with observations from timekill curve studies in human whole blood, where ciprofloxacin showed superior bactericidal activity compared to norfloxacin or ofloxacin. The amounts of unchanged drug excreted in urine (48 h period) were found to be 35%, 24% and 77% for ciprofloxacin, norfloxacin and ofloxacin respectively, indicating different excretion kinetics. The volumes of urine excreted in the different collection periods were comparable for the three drugs tested. Mean urine concentrations for ciprofloxacin were higher during the 0 to 4 h collection periods, whereas ofloxacin was excreted into the urine over a longer time period. Measurements of urine bactericidal activity showed that ciprofloxacin had the highest titers during the early collection periods, whereas the prolonged excretion of ofloxacin did not result in higher urine bactericidal titers, compared to ciprofloxacin.

Inhibition of gastric secretion in man by rioprostil, a new synthetic methyl prostaglandin E1.

The effect of rioprostil, a new synthetic prostaglandin (PG) E1 (2-decarboxy-2-hydroxymethyl-15-deoxy-16RS-hydroxy-16-methyl PGE1), on basal and pentagastrin stimulated gastric secretion was investigated in a placebo controlled double-blind crossover study in 6 healthy male volunteers. Rioprostil reduced both basal and stimulated gastric secretory volume, as well as acid and pepsin secretion. At doses of 300 and 600 micrograms rioprostil reduced basal acid secretion by 54 and 88% and basal pepsin secretion by 86 and 68%, respectively. The two doses of rioprostil reduced stimulated acid secretion by 44 and 59% and stimulated pepsin secretion by 40 and 67%, respectively. Loose stools were observed in three subjects, other side-effects were minor and not different as compared to placebo. It is concluded that rioprostil is a potent inhibitor of both acid and pepsin secretion in man.

Food and muzolimine interaction.

The influence of food on the bioavailability of muzolimine was investigated in a non-controlled cross-over study. Six healthy volunteers received 40 mg muzolimine directly after a standardized American breakfast (non-fasting volunteers) and, one week later, after an overnight fast with breakfast 90 min after drug intake (fasting volunteers). The concentrations of muzolimine in plasma and urine were determined between 0 and 48 h after administration. Results (means +/- SEM): in the fasting volunteers, the areas under the muzolimine plasma level curves (0-32 h) were higher than in the non-fasting volunteers (3002 +/- 390 vs. 2038 +/- 344 ng X h/ml, p less than 0.001), the peak concentrations were higher (332 +/- 36 vs. 176 +/- 38 ng/ml, p less than 0.05) and appeared earlier (1.8 +/- 0.2 h vs. 4.0 +/- 0.5 h, p less than 0.01). Also, the urinary volumes and sodium excretion were higher in the fasting volunteers than in the non-fasting volunteers. Hence, the bioavailability of muzolimine is reduced if administered after a meal which should be considered in the treatment schedule.

Pharmacokinetics of ciprofloxacin after oral and intravenous administration in healthy volunteers.

The pharmacokinetics of ciprofloxacin (Bay o 9867) was examined after a single oral dose of 250 mg and a single intravenous dose of 100 mg respectively in six healthy male volunteers in an open, randomized crossover study. Although ciprofloxacin concentrations were measured in serum, plasma and urine by HPLC with fluorimetric detection and by microbiological assay, all pharmacokinetic calculations are based on the highly sensitive HPLC method only. The mean serum concentration of ciprofloxacin peaked approximately 1 h after the oral dose (0.94 mg/l). The elimination half-life was about 4 h and the renal clearance was 4.75 ml/min . kg; both were independent of the route of administration. The total clearance (9.62 ml/min . kg) was about twofold higher than the renal clearance. The volume of distribution of the central compartment was calculated to be 0.161 l/kg and the total volume at steady state was 2.0 l/kg. About 27% of the oral dose was excreted in urine, whereas the urinary recovery of the i.v. dose was 46%. The absolute bioavailability of ciprofloxacin was found to be approximately 60%. Ciprofloxacin appears to follow first-order, three compartment model kinetics.

High-performance liquid chromatographic method for the quantitative analysis of a synthetic copolymer with antitumor activity (copovithane) and methylamine in human blood plasma and urine.

A method for the determination of a synthetic polymeric compound with antitumor activity (copovithane) and methylamine in blood plasma and urine is described. Copovithane is prepared by radical polymerisation of a diurethane with N-vinylpyrrolidone. The method is based on high-performance liquid chromatography of the methylamine hydrochloride which arises during the hydrochloric acid hydrolysis of the parent substance. The methylamine hydrochloride is converted to the trinitrobenzenesulphonyl derivative for the purpose of chromatographic detection. The limit of determination for copovithane in blood plasma is 1.2 mg/l and in urine 1.5 mg/day. The determination limit for methylamine in blood plasma is 0.2 mg/l and in urine 0.3 mg/day. The imprecision is dependent on the sample, and amounts to +/- 6.8% for blood plasma and +/- 6.4% for urine.

Correlation of adrenocorticotropic activity of ACTH analogs with degree of binding to an adrenal cortical particulate preparation.

This study deals with the interaction of polypeptide hormones with their receptors. Specifically it involves the binding of synthetic ACTH analogs and fragments to a particulate fraction from beef adrenal cortical tissue. This fraction was found to bind synthetic [(14)C-Phe] [Gln(5)]beta-corticotropin(1-20) amide but failed to bind significant amounts of [(14)C-Phe] [Gln(5)]beta-corticotropin(1-10). The former peptide exhibits a high degree in vivo adrenocorticotropic activity in the rat; the latter is inactive. [(14)C-Phe] [Gln(5)]beta-corticotropin(1-20) amide exhibited little affinity for similarly prepared particulates from beef kidney, liver, or adrenal medulla. Using a series of synthetic homogeneous nonradioactive analogs or fragments of beta-corticotropin(1-20) amide to displace [(14)C-Phe] [Gln(5)]beta-corticotropin(1-20) amide from the particulate fraction a significant correlation between binding and in vivo adrenocorticotropic activity was established. Major "active" and "binding" sites were shown to reside in different sections of the ACTH molecule. Charged groups play a major role in the attachment of ACTH to the particulate fraction and the sequence Lys-Lys-Arg-Arg proved to be particularly significant. The high degree of binding specificity for ACTH peptides which is exhibited by the particulate suggests that it contains ACTH receptor(s). Moreover, the striking similarity between observations with the S-peptide-S-protein model system and the system described would seem to indicate that the ACTH receptor is a protein.