Trapping of short-lived intermediates in phospholipid phase transitions: the L* alpha phase

Time-resolved small-angle X-ray diffraction of liquid-crystalline phospholipid-water systems under temperature or pressure jump conditions has demonstrated the existence of an ordered, intermediate L alpha phase, with a sub-second lifetime, designated as the L* alpha-phase. The lamellar repeat spacing is, universally, 0.3 nm smaller than that of the parent phase, irrespective of the lipid composition and of the jump conditions, provided that the jump leads to a net volume expansion of the phase. The presence of salts, most notably LiCl, leads to a prolongation of the lifetime. The results suggest a non-monotonic potential function for the interbilayer water thickness.

Safety and tolerability of naproxen ophthalmic solution in comparison to placebo

BACKGROUND

Naproxen is a classic non-steroidal anti-inflammatory drug (NSAID) with established analgesic and anti-inflammatory potency. Its action is related to cyclooxygenase inhibition and consequent decrease in prostaglandin concentration in various fluids and tissues. Since prostaglandin release is involved in several ocular alterations, various NSAID eye drops have come into use in the clinical setting during the last decade.

SUBJECTS, MATERIAL AND METHODS

A randomized, double-blind, placebo-controlled, three-way crossover design phase I was performed in 12 healthy volunteers to determine both tolerance and safety of a new NSAID ophthalmic solution containing sodium naproxen (0.1% and 0.2%). Both single dose and repeated dose (TID for 6 days) instillation were performed. Evaluation was entirely based upon tolerance criteria. Subjective and objective signs of ocular irritation and subject comfort preference were evaluated. Also medical examination, hematology, blood chemistry and urine analysis were also assessed to evaluate any possible effect of the test drugs and control.

RESULTS

Neither ophthalmic tolerance parameters nor vital signs or laboratory parameters were influenced by treatments. A slight hyperemia of the conjunctiva was the only change observed in the eye during the study, whereas the only symptom mentioned was burning.

CONCLUSION

It is concluded that both tolerability and safety of 0.1% and 0.2% naproxen solution are acceptable after single and repeated conjunctival administration.

Safety, tolerability and pharmacokinetics of the new long-acting quinolone DW-116 after single and multiple dosing in healthy subjects

The safety, tolerability and pharmacokinetics of DW-116, a new fluoroquinolone with a broad antibacterial spectrum, were evaluated in healthy male subjects after administration of single oral doses of 100, 200, 300 and 800 mg and after administration of multiple oral doses of 300 or 400 mg, respectively, for 7 days. DW-116 was well tolerated. Gastrointestinal symptoms and skin reactions were noted and considered to be possibly related to DW-116. The geometric means of the maximum plasma concentrations (Cmax) linearly increased with the dose administered from 1.19 mg/L to 8.73 mg/L after single dose administration. At steady state, the geometric mean minimum and maximum plasma concentrations were 2.14 and 5.65 mg/L, respectively, after the multiple 300 mg dose and 2.73 and 8.00 mg/L, respectively, for the multiple 400 mg dose. Tmax varied between 1 and 5 h. The terminal half-life ranged from 11.37 to 24.89 h. The geometric mean renal clearance was approximately 30 mL/min. Approximately 45% of the dose was excreted unchanged in urine within 60 h. There was no clinically relevant deviation from dose proportionality. The changes in steady-state pharmacokinetic parameters when DW-116 was taken before a high-fat breakfast were not clinically relevant. In conclusion, DW-116 was safe in this study, the first administration to human subjects. Its pharmacokinetics indicate that once-daily dosing may be possible.

Lalpha-phase separation in phosphatidylcholine-water systems induced by alkali chlorides

The effects of alkali chlorides on phosphatidylcholine-water bilayer systems in the Lalpha-phase were investigated by using small- and wide-angle X-ray scattering. The ternary system LiCl-POPC-H2O under isothermal conditions has shown that above Li+/POPC molar ratios of 0.1 and a lipid concentration above 5% (w/w), a splitting of the lamellar Bragg diffraction peaks into discrete components indicates a phase separation into different lamellar liquid crystalline (smectic A) phases. It is also shown that in saturated distearoyl phosphatidylcholine and in egg phosphatidylcholine, alkali chlorides induce Lalpha-phase separation. The number and repeat distance of the coexisting lamellar phases depend on the nature and concentration of the alkali chloride, the concentration of the phosphatidylcholine, and the degree of the acyl chain unsaturation.

[The effect of food on theophylline absorption]

The possible influence of the food and fat content of meals on the bioavailability and pharmacokinetics of a 350 mg sustained release theophylline (CAS 58-55-9) preparation (Bronchoretard) was investigated after single dose oral administration to 18 volunteers in a randomised 3-way crossover design. The treatments investigating administration of the test preparation in a fasting state, after a standard meal and after a high-caloric fat evening meal, according to commonly applied rules, were shown to be equivalent with respect to the extent of bioavailability (AUC) and the observed maximal concentration (Cmax). Pharmacokinetic parameters describing sustained release characteristics were not changed to any relevant degree. As expected, the co-administration of food resulted in a physiologically determined delay in absorption, which is probably not therapeutically relevant during long-term administration.

[In vivo verification of in vitro release specifications of a theophylline sustained-release preparation]

Especially in drugs with a narrow therapeutic range, "within product bioequivalence" i.e. "batch-to-batch bioequivalence" should be scrutinized. Therefore, pharmacokinetics and bioavailability of to batches at the upper and lower in vitro specification range as well as a batch representing the middle of the specification range was evaluated in an in vivo bioequivalence study. An open, randomized, 3-way crossover, multiple dose study in 18 healthy, male volunteers was selected for this purpose. Bioequivalence regarding rate (Cmax ss; t75%Cmax) and extent (AUCss) of absorption could be established for both extreme batches at the lower and upper in vitro specification range. Additionally both batches proved to be bioequivalent compared to the batch in the middle of the in vitro specification range. As a result, reproducible concentration-time profiles can be guaranteed for all batches of this sustained release theophylline (CAS 58-55-9) preparation. Furthermore, pharmacokinetic characteristics of all three batches meet the quality criteria defined for sustained release theophylline preparations, guaranteeing optimal concentration/time profiles for the therapy of asthma.

[Pharmacokinetics of a new fluid theophylline sustained-release drug form. Microcapsules in a sachet]

A new sustained release theophylline (CAS 58-55-9) formulation was especially designed for the elderly and children. Microcapsules of theophylline, administered as a suspension in water, proved to be a suitable dosage form for a clientele with impaired or difficult deglutition. Pharmacokinetic characteristics of 2 batches at the lower (T1) and upper (T2) in vitro dissolution specification range of this new formulation and a pellet formulation (R) as a comparator were evaluated in an open, randomised, 3-way, multiple dose, crossover study with an asymmetric dosage regimen of 400 mg and 200 mg theophylline. Smooth and safe plasma concentrations with a high and long-lasting plateau were achieved with this new formulation. Plateau times which are independent of the asymmetric dosage regimen ranged from 16.4 h (T1) to 13.8 h (T2) and could therefore cover sufficient time of the dosage interval. Maximum plasma levels of 9.6 micrograms/ml and 10.0 micrograms/ml were attained 6.6 and 6.1 h after dosing of T1 and T2, coinciding perfectly with the time of the critical morning dip at 2-6 a.m. With a nocturnal excess of 15.5% (T1) and 17.9% (T2), this circadian-tailored asymmetric dosage regimen proved to take into account the chronopathology of asthma and the chronopharmacokinetics of theophylline sustained release preparations. Bioequivalence of all 3 formulations compared with each other with regard to rate (Cmax ss) and extent (AUCss) of absorption could be established for the 2 batches at the upper and lower in vitro specification range and for both batches of the new formulation compared to the reference. All in all, the safety and efficacy of this new liquid sustained release theophylline preparation could be established. Furthermore, in vitro specifications were justified according to current EC guidelines.

[Revalidation of the in vitro specification limits after an in vitro-in vivo correlation]

A "Level A" in vitro/in vivo correlation was established for a sustained release theophylline (CAS 58-55-9) preparation (Bronchoretard) under investigation. Such a functional relationship is a valuable tool for predicting the in vivo performance of a product. Additionally, the in vitro specification limits could be justified or even enlarged based on such an extrapolation.

[Pharmacokinetics of a theophylline sustained-release formulation after single and twice daily dosage]

Sustained release theophylline (CAS 58-55-9) preparations may be dosed once or alternatively twice-a-day, depending on the intention of a theophylline therapy. A once-a-day dosage regimen is considered appropriate in patients with nocturnal asthma attacks, whereas a twice-a-day regimen is advantageous for guaranteeing bronchodilatation and to control the underlying inflammatory disease. Therefore, pharmacokinetic characteristics of both modes of administration were evaluated in a randomised, two-way crossover study in 18 female and male elderly volunteers under multiple-dose conditions. The shape of the pharmacokinetic profiles showed the expected and pronounced differences, while the extent of absorption was bioequivalent. Twice daily administration decreased the nocturnal maximum concentration and at the same time increased the minimum concentration. At the expense of the nocturnal excess, the peak-trough fluctuations (PTF) were reduced from 92.1% to 39.5%. Plateau times of 11.4 h and 20.2 h were achieved with both modes of administration. As for theophylline with its narrow therapeutic range, high quality sustained release preparations distinguish themselves by long plateau times and small peak-trough fluctuations such as those observed with the preparation under investigation. When using this preparation, therapeutic concentrations necessary for safety and efficacy are assured under either a once- or a twice-daily dosing regimen.

[Absorption profile and absolute bioavailability of a theophylline sustained-release preparation]

In a single-dose crossover study with 16 healthy male nonsmoking volunteers the absorption profile and absolute bioavailability of the sustained release pellets contained in all dosage strengths of Bronchoretard (100, 200, 350, 500 mg anhydrous theophylline) were investigated. One capsule (500 mg theophylline) was given after an evening meal. The reference treatment consisted of an i.v. infusion over 8 h in a total dosage of 350 mg theophylline. Plasma concentration-time profiles were evaluated for 72 h after dosing, respectively start of infusion. Theophylline was measured by high-performance liquid chromatography (HPLC). Absorption profiles (Wagner-Nelson) were derived and the absolute bioavailability was calculated. For the sustained release pellets a liberation/absorption of zero order for 12 h could be noted; the dose-corrected mean absolute bioavailability was 88%. The assumptions of an investigation on absolute bioavailability are discussed and the limitations on generalizability resulting therefrom.

Pharmacokinetic characteristics of a new liquid sustained-release formulation of theophylline designed for the elderly and children: microcaps as sachet

A new sustained-release theophylline formulation was especially designed for the elderly and children. Microcapsules of theophylline, administered as a suspension in water, proved to be a suitable dosage form for a clientele with impaired or difficult deglutition. Pharmacokinetic characteristics of 2 batches at the lower (T1) and the upper (T2) in vitro dissolution specification range of this new formulation and a pellet formulation (R) as a comparator were evaluated in an open, randomized, 3-way, multiple-dose, crossover study design with an asymmetric dosage regimen of 400 mg and 200 mg theophylline. Smooth and safe plasma concentrations with a high and long-lasting plateau were achieved with this new formulation. Plateau times which are independent of the asymmetric dosage regimen ranged from 16.4 hours (T1) to 13.8 hours (T2) and could therefore span sufficient time of the dosage interval. Maximum serum levels of 9.6 micrograms/ml and 10.0 micrograms/ml were attained 6.6 and 6.1 hours after dosing of T1 and T2, coinciding perfectly with the time of the critical morning dip at 2-4 a.m. With a nocturnal excess of 15.5% (T1) and 17.9% (T2) this circadian-tailored asymmetric dosage regimen proved to take into account the chronopathology of asthma and the chronopharmacokinetics of theophylline sustained-release preparations. Bioequivalence of all 3 formulations versus each other with regard to rate (Cmaxss) and extent (AUC(tau)ss) of absorption could be established for the 2 batches at the upper and lower in vitro specification range and for both batches of the new formulation compared to the reference. All in all, safety and efficacy of this new liquid prolonged-release theophylline could be established. Furthermore, in vitro specifications could be justified according to current EU guidelines.

Bioequivalence evaluation of two preparations containing the highly variable compound selegiline (L-deprenyl)

Selegiline, used in the treatment of Parkinson's disease, inhibits the intracerebral degradation of dopamine and the uptake of catecholamines. Due to a high volume of distribution and also a high rate of biotransformation the concentrations of selegiline in plasma are rather low. In addition, there are indications that selegiline binds to erythrocytes. An open, randomized, 2-way cross-over study was performed in 24 healthy male volunteers to determine bioavailability and pharmacokinetic parameters of 2 oral selegiline preparations after single dose administration. Statistical tests were applied to the pharmacokinetic parameters AUCinf, AUC0-8, AUCz, Cmax and tmax. The terminal half-lives t1/2 for selegiline with geometric means of 1.69 h (n = 22) and 1.76 h (n = 21) for treatments A and B and for N-desmethyl-selegiline with geometric means of 1.98 h and 1.96 h for treatments A and B agreed very well. AUCinf of selegiline could be compared between treatments for 14 subjects only. The geometric mean ratio was 97.80% with a 90% confidence interval that ranged from 79.58%-120.17% and thus exceeded the (80%, 125%) range by a very small margin. After correction for the actual dose contained in each of the 2 preparations the geometric mean ratio was calculated to 98.39% with a 90% confidence interval that ranged from 80.06%-120.90% and thus was fully contained within the (80%, 125%) acceptance range. Treatments also agreed very well with respect to AUCinf of N-desmethyl-selegiline, the active metabolite of selegiline, with a geometric mean ratio of 96.14% with a 90% confidence interval that ranged from 92.41%-100.01% so that bioequivalence of the 2 treatments could be shown very clearly with respect to this metabolite. The AUC of N-desmethyl-selegiline in serum is about 6-fold higher than that of the parent drug. It is assessed with low variability. Thus, it is reasonable to base the judgement for or against bioequivalence primarily on the data obtained for the metabolite although "a larger acceptance range may be acceptable if inevitable and clinically acceptable" for the parent compound selegiline which certainly can be classified as a "highly variable compound".

Three explorative studies on the efficacy of the antihistamine mebhydroline (Omeril)

The efficacy of a multiple oral dose treatment with mebhydroline (Omeril coated tablets, 100 mg t.i.d.) was examined in 3 studies which were performed in a randomized, double-blind and placebo-controlled 2-way cross-over design. A second target was to investigate the suitability of different pharmacodynamic models for testing the efficacy of antihistamines. Study A involved a nasal provocation with a specific allergen in 11 symptom-free patients suffering from seasonal allergic rhinitis. In study B, a nasal provocation with histamine was investigated in 11 healthy volunteers. Study C involved a cutaneous provocation with a specific allergen in 12 symptom-free patients suffering from seasonal allergic rhinitis/atopy. The mebhydroline treatment's superiority over placebo was shown statistically at the 95% confidence level for the symptoms itchy nose in study A and for nasal congestion in study B. In study C, allergen-induced weals (planimetric measurement) and itching (visual analog scale) were significantly changed by mebhydroline. A qualitative evaluation revealed a reaction intensity that differed between the 2 treatments to a clinically relevant degree, however, without reaching significance. On the basis of the data it is expected that the clinical efficacy of mebhydroline may be further substantiated in confirmatory clinical trials which should include placebo and positive controls. The test methods used differed in their suitability for measuring the pharmacodynamic effects of antihistamines. Overall, the most clear-cut results were seen in hay fever patients using a specific allergen for provocation. The planimetric assessment of weal response should be preferred as a cutaneous model. Both AR and AARM have their clinical relevance. Based on highly significant results of a subgroup analysis there are indications in favor to AR, but momentary there is no definite conclusion in favor of or against either of the 2 methods.

Gastrointestinal blood loss induced by three different non-steroidal anti-inflammatory drugs

A clinical study was performed on 18 healthy volunteers to compare the gastrointestinal daily blood loss induced by oral intake of three different non-steroidal anti-inflammatory drugs, lysine clonixinate (CAS 55837-30-4), ibuprofen (CAS 15687-27-1) and acetylsalicylic acid (CAS 50-78-2 ASA). For quantitative determination of gastrointestinal blood loss, autologous erythrocytes were radiolabelled in vitro with 51Cr and reinfused at study start. The amount of radioactivity excreted in faeces was measured during a placebo baseline phase of three days, a treatment phase of five days with thrice daily dosing of ASA, ibuprofen or lysine clonixinate and a subsequent wash-out phase of five days. The highest increase of mean daily blood loss over baseline was observed after treatment with ASA (+ 1.66 ml/d versus baseline). Treatment with ibuprofen led to an increase of mean daily blood loss by + 0.52 ml/d. During treatment with lysine clonixinate the mean increase of daily blood loss was +0.32 ml/d versus baseline. In the ibuprofen and lysine clonixinate treatment groups the values of mean daily blood loss decreased during the wash-out phase with respect to the verum phase, whereas the mean daily blood loss during the wash-out phase after treatment with ASA even increased in comparison to the verum phase (mean daily blood loss: +2.07 ml/d versus baseline.

[The pharmacokinetics and bioavailability of a new mexiletine preparation in healthy volunteers]

In the course of this study, both the bioavailability and the most important pharmacokinetic parameters of a newly development mexiletine (CAS 31828-71-4) preparation (Mexiletine-ratiopharm mite, dosage 200 mg of mexiletine) were to be determined in comparison to a commercial reference preparation registered according to the AMG 1976, after single oral administration. For this purpose, the test and the reference preparation were examined in healthy male volunteers according to a randomized, 2-way crossover design. Both preparations entrained maximum plasma levels of approx. 300 ng/ml 3.5-4 h following administration. For the areas under the curve, values around 4000 h x ng/ml were found; the plasma half-life of the test preparation was 7.55, for the reference preparation 7.75 h. The statistical comparison (ANOVA, confidence interval according to Westlake, Pratt-Wilcoxon-Test) of the pharmacokinetic parameters obtained in the study clearly resulted in bioequivalence of the newly developed mexiletine preparation and the reference drug. No side effects worth mentioning were observed after administration of either preparation, thus good and comparable clinical tolerability of both preparations may be presumed.

Bioequivalence evaluation of two glyceryl trinitrate patches after 12-h usage in healthy volunteers

The study objective was to determine the bioavailability and main pharmacokinetic parameters of glyceryl trinitrate (GTN, CAS 55-63-0) following cutaneous application of two different glyceryl trinitrate patches using a randomized cross-over design. The two patches investigated were Deponit 5 (a newly developed test patch) and an already marketed reference patch. Thirty-seven healthy male volunteers were included in this study; 36 of them completed the investigation. Blood samples were withdrawn up to 15 h after start of patch application and plasma concentrations of glyceryl trinitrate were quantified by a GC/MS method. For the areas under the curve from time 0 to the last quantifiable sample, AUC(O-Tlast), mean values of 1545 (test patch, n = 35) and 1686 h.pg/ml (reference patch, n = 35) were found. The corresponding peak glyceryl trinitrate plasma levels were 253 and 263 pg/ml, respectively; they were reached after 6.58 h (test patch) and 7.72 h (reference patch). The statistical comparison (ANOVA, confidence intervals) of the pharmacokinetic parameters found in the study resulted in bioequivalence of both patches. Typical side-effects known and described under glyceryl trinitrate therapy were also observed in this study.

Bioequivalence evaluation of the metabolites 1,2 and 1,3-glyceryl dinitrate of two different glyceryl trinitrate patches after 12-h usage in healthy volunteers

In the course of this study both the bioavailability and main pharmacokinetic parameters of the glyceryl trinitrate (GTN, CAS 55-63-0) metabolites 1,2 and 1,3-glyceryl dinitrate (1,2-GDN and 1,3-GDN) were to be determined following transdermal application of a glyceryl trinitrate test patch (Deponit 5) and an already marketed reference patch. For this purpose, both patches were examined in healthy volunteers according to a randomized two-way cross-over design, blood samples were withdrawn up to 15 h after start of patch application and the plasma concentrations of both metabolites were quantified using a GC/MS method. The investigation showed the following results: Metabolite 1,2-glyceryl dinitrate: For the area under the curve from time 0 to the last quantifiable sample (AUC(0-Tlast) arithmetic mean values of 23.77 h.ng/ml (test patch) and 27.83 h.ng/ml (reference patch) were found. The corresponding peak plasma levels were 2.45 ng/ml and 2.93 ng/ml, respectively; they were reached after 6.4 h (test patch) and 8.31 h (reference patch). Metabolite 1,3-glyceryl dinitrate: The arithmetic mean values for AUC(0-Tlast) were 3.32 h.ng/ml (test patch) and 3.81 h.ng/ml (reference patch). The maximum plasma levels were 0.35 ng/ml and 0.41 ng/ml for the test and reference preparation, reached after 6.4 h and after 7.86 h, respectively. The statistical comparison (ANOVA, confidence intervals) showed bioequivalence between both patches concerning the metabolites investigated. The typical side effects known after nitrate therapy also occurred in the course of this study.

Study on the influence of food on the absorption of theophylline from a controlled-release preparation

The possible influence of food and fat content of meals on the bioavailability and pharmacokinetics of a 350 mg sustained-release theophylline (CAS 58-55-9) preparation (Bronchoretard) was investigated after single-dose oral administration to 18 volunteers in a randomized 3-way cross-over design. The treatments investigating an administration of the test preparation in a fasting state, after a standard meal and after a high-caloric fat evening meal, according to the commonly applied rules, could be shown to be equivalent with respect to the amount of bioavailability (AUC) and the observed maximal concentrations (Cmax). Pharmacokinetic parameters describing sustained-release characteristics were not changed either to any relevant degree. As expected, the co-administration of food resulted in a physiologically determined delay in absorption, which probably is not therapeutically relevant during long-term administration.

Bioavailability and pharmacokinetics of a fixed combination of delapril/indapamide following single and multiple dosing in healthy volunteers

The study objective was to obtain detailed information on the bioavailability and pharmacokinetics of the new fixed combination of delapril and indapamide following single and multiple dosing. For this reason, the study was performed in two parts, separated by a medication-free period of at least 7 days. In the single dose part, one tablet, containing 30 mg delapril and 2.5 mg indapamide, was administered to 12 male volunteers; in the multiple dose part, the volunteers received one tablet of the test preparation, once daily over 7 days. Following single and on the last day of the multiple dosing regimen, blood samples were withdrawn and serum concentrations of delapril and its metabolites M1, M2 and M3 and whole blood concentrations of indapamide were quantified by means of HPLC methods. In addition, urine samples were collected following single and multiple dosing for evaluation of the cumulative amount of delapril and its metabolites M1-M3 excreted in urine. For the area under the curve, calculated from time 0 to infinity (AUC(0-infinity)) the study revealed, following single dosing, mean values of delapril and its metabolites M1, M2 and M3 of 281, 2178, 739 and 716 h.ng/ml, respectively; for indapamide the mean value was 1597 h.ng/ml. The corresponding mean values found after multiple dose administration were 272, 2071, 857 and 598 h.ng/ml for delapril and its metabolites, respectively and 1536 h.ng/ml for indapamide. Evaluation of the cumulative amount of delapril and its metabolites M1-M3 excreted in urine (Ae) demonstrated mean values following single dosing (observation period 36 h) of 705, 4521, 454 and 4203 micrograms, respectively; the corresponding values after multiple dose administration (observation period 24 h) of the test preparation were 655, 4679, 469 and 4801 micrograms, respectively. The most important pharmacokinetic parameters AUC(0-infinity) and Ae were statistically compared by analysis of variance (ANOVA) and 90% confidence intervals were calculated. It may be concluded from the results of this study, that the bioavailability and pharmacokinetic parameters of the test preparation after single dosing and after multiple doses correspond well. The undesired side effects observed are known to occur after administration of the test preparation. The occurrence was a little more frequent after multiple dose application in comparison with the single dose administration.

Bioavailability and pharmacokinetics of a new isosorbide dinitrate spray preparation in healthy volunteers

In the course of this study the bioavailability and pharmacokinetic profile of a newly developed 2.5 mg (per valve release) oral isosorbide dinitrate (ISDN, CAS 87-33-2) spray preparation (Isoket Spray) were determined and compared with the results for an already marketed reference spray preparation following single application. For this purpose, the test and reference spray were examined in 18 healthy volunteers according to a randomized 2-way cross-over design. Blood samples were collected during 12 h p.a. and plasma concentrations of ISDN and its metabolites isosorbide-2-mononitrate (IS-2-MN) and isosorbide-5-mononitrate (IS-5-MN) were quantified by a GC-method. Both sprays showed mean maximum concentrations of ISDN in plasma of nearly 18 ng/ml about 7 min after drug intake with arithmetic mean values for the areas under the curve AUC0-12 of 7.01 (test spray) and 7.30 h.ng/ml (reference spray). For the metabolic products IS-2-MN and IS-5-MN (values for the reference spray in brackets) the corresponding maximum concentrations were 4.15 (4.21) ng/ml and 16.1 (15.9) ng/ml, respectively, and for the areas under the curve AUC0-12 values of 9.75 (9.92) h.ng/ml for IS-2-MN and 104.3 (99.7) h.ng/ml for IS-5-MN in the mean were calculated. Statistical evaluation of all pharmacokinetic parameters revealed bioequivalence between the two preparations. Typical side-effects known and described under isosorbide dinitrate therapy were also observed in this study.

Evaluation of pharmacokinetics, bioavailability and dose linearity of diltiazem in healthy volunteers

The objective of this randomized five-way cross-over study with healthy male volunteers was to determine, one the one hand, the bioavailability and main pharmacokinetic parameters of 4 sustained release diltiazem (Surecaps, CAS 42399-41-7) test preparations with ascending doses (180, 240, 300, 360 mg), administered as single application, versus an immediate release 60 mg diltiazem reference preparation, which was given thrice a day at 8-h intervals. On the other hand, the study also allowed the evaluation of a possible dose linearity of the test substance diltiazem. Plasma concentrations of diltiazem and its major metabolite desacetyl-diltiazem were measured by high pressure liquid chromatography (HPLC) up to 48 h after single dosing of the sustained release preparations as well as after repeated doses of the immediate release formulation. The undesired side effects/concomitant symptoms observed are known to occur after diltiazem administration. For the area under the curve, e.g. calculated from time 0 to the last quantifiable sample (AUC0-Tlast), the study revealed for the parent compound diltiazem mean values of 926.2, 1602.4, 1873.2 and 2415.7 h.ng/ml after administration of the 4 sustained release test preparations, respectively; for the immediate release reference preparation the value was 1007.2 h.ng/ml. Concerning the main metabolite desacetyl-diltiazem the corresponding values for the 4 sustained release formulations were 138.6, 236.9, 280.2 and 345.6 h.ng/ml, respectively. The corresponding value for the immediately release formulation was 127.5 h.ng/ml. Concerning a possible dose linearity of diltiazem, statistical analysis revealed a convincing linear relationship between at least 3 of the 4 sustained release preparations, therefore linearity may be assumed between 240 and 360 mg.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of pharmacokinetic interactions between moxonidine and digoxin

The potential for pharmacokinetic interactions between moxonidine and digoxin at steady-state was investigated in 15 healthy male volunteers. Multiple oral doses of 0.2mg moxonidine twice daily and 0.2mg digoxin once daily were administered alone and in combination in a randomised 3-period crossover design. The drugs were administered for at least 5 days. The results indicate that neither moxonidine nor digoxin influences the pharmacokinetics of the other drug under steady-state conditions.

Evaluation of bioavailability and pharmacokinetics of two isosorbide-5-mononitrate preparations in healthy volunteers

The objective of this study was to determine both the pharmacokinetic parameters and the bioavailability of two commercial 20-mg isosorbide-5-mononitrate (IS-5-MN) preparations (test and reference preparation) after single oral administration. For this purpose, the test and the reference preparation were examined in 24 healthy male volunteers according to a randomized 2-way cross-over design, blood samples were withdrawn up to 24 hours postadministration, and plasma concentrations of IS-5-MN were quantified by a gas chromatography (GC) method. Both preparations led to peak plasma levels of approximately 360 ng/mL IS-5-MN in the mean 0.76 hour (test) and 0.94 hour (reference preparation) after application; the plasma half-lives were about 5.2 hours, and for the areas under the curve (AUC(0-infinity)), mean values of 2741 (test preparation) and 2742 hour.ng/mL (reference preparation) were found. The statistical comparison (analysis of variance, confidence intervals) of the pharmacokinetic parameters found in the study resulted in bioequivalence of both IS-5-MN preparations. The undesired side effects/concomitant symptoms observed are known to occur after IS-5-MN administration.