Bioavailability of two hydrochlorothiazide preparations

Summary Eight healthy volunteers received hydrochlorothiazide 75 mg as Dichlotride and Esidrex. Maximal plasma levels were significantly (p<0.05) higher after Dichlotride than Esidrex, 512±189 and 376±70 ng/ml, respectively. However, the bioavailability of the two brands of hydrochlorothiazide did not differ significantly as judged by comparison of the AUC_09h and AUC₀, and the urinary recovery of hydrochlorothiazide during 48 hrs.Supported by the Swedish Medical Research Council (Grant No. B 75-04X-227-12 C) and Hässle-Ciba-Geigy AB, Gothenburg, Sweden     

Bioavailability of different preparations of paracetamol

1 Plasma drug concentrations in eight volunteer subjects following oral administration of six preparations of paracetamol have been studied.

2 Significant interindividual differences in plasma paracetamol concentration were found within 1 h but there were no consistent differences between the different drug preparations. The results indicate that all the preparations have equivalent bioavailability.

3 In four subjects, tested with the same preparation on two occasions, the findings suggest that drug absorption may differ from one occasion to another.

     

Bioavailability of two tablet preparations of carbimazole in man

1. The bioavailability of two 5 mg tablet formulations of carbimazole (Neomercazole [A] and Carbazole [B]) have been compared in six euthyroid subjects. There was considerable inter-patient variation in absolute bioavailability although, for each subject, peak plasma concentrations of methimazole were similar with both formulations. 2. Mean peak plasma concentrations were seen on average 62 min after administration of tablet A as compared to 40 min after tablet B. This is consistent with the finding that the disintegration and dissolution times were shorter for formulation B than for formulation A. The mean area under the plasma concentration curve and the 6 h plasma concentration of methimazole tended to be greater after tablet A. These differences could be of significance in the treatment of thyrotoxicosis.     

Bioavailability of phenytoin. A comparison of two preparations

Summary Plasma phenytoin levels were measured in 60 patients under steady-state conditions for a period of six weeks. During the trial, the preparation of phenytoin was changed from Phenytoin BP (Regent) to Epanutin Infatabs. A significant increase in plasma phenytoin levels following the change of tablet was matched by a decrease in the number of seizures.     

Bioavailability of nifedipine: A comparison between two preparations

In a random cross-over study, eight healthy volunteers received single 10 mg doses of either nifedipine capsule (Adalat, Bayer) or nifedipine tablets (Taro) after an overnight fast. The areas under the serum concentration time curves were not significantly different (AUC^{0→ ∞} 319·8 ± 28·0 (SEM) ng ml^?1 h^?1 for capsules, 260·8 ± 15·3 ng ml^?1 h^?1 for tablets). The peak serum levels and the time of their occurrence were 162·4 ± 23·4 ng ml^?1 at 30 min for capsules and 43·0 ± 3·0 ng ml^?1 at 1–2 h for tablets, indicating that the absorption of nifedipine from the capsule is faster than from the tablet form. Clinical symptoms of vasodilation corresponded with the nifedipine peak levels. We conclude that although the bioavailability in general of the two preparations is similar, the therapeutic equivalence may differ. Depending on the therapeutic indication each preparation may have its merits.     

Bioavailability of four different pharmaceutical preparations of carbamazepine.

The bioavailabilities of two tablet brands carbamazepine (CBZ) (Tegretol, A; Neurotol, B) were compared with two new experimental preparations (C,D). Formulation A showed a more sustained release nature than did the other formulations. The AUCs0 leads to infinity gave no significant differences between treatment A and three other treatments. However, if AUC0 leads to 72 was calculated instead of AUC0 leads to infinity, the preparation A gave the significantly lower bioavailability than the other compounds. Formulations A and B are marketed as generically equivalent preparations in Finland. However, their pharmacokinetic parameters after a single dose were different.     

Bioavailability of digoxin from rapidly dissolving preparations

1 Intestinal absorption of digoxin was assessed by determination of peak plasma concentrations, areas under plasma concentration curves over 80 h, and 10 day urinary excretion. Absorption was equal after ingestion of single doses of standard Lanoxin (Wellcome) tablets, tablets and capsules of ultra-rapid dissolution rate material, or an oral solution of digoxin in water.

2 Mean plasma concentrations and dosage-interval urinary excretion were highly similar during 14 day courses of either Lanoxin or ultra-rapid dissolution tablets. Increased bioavailability does not result from encapsulation of solid dosage presentations, nor from increasing tablet dissolution rate beyond 75% in 15 minutes.

3 Fourteen day courses of tablets of slow dissolution rate produced lower and less consistent mean plasma concentrations and urinary excretion. Slow dissolution rates are associated with greater individual variability in absorption.

     

Bioavailability and dissolution of different formulations of oxytetracycline preparations.

1 The concentration of oxytetracycline in plasma was studied by microbiological assay after oral administration of five different preparations of the antibiotic. None of these preparations had been studied previously. 2 There was a statistically significant correlation between the time required for 50% dissolution at pH 2 and biological availability, as assessed by the peak plasma level or the area under the plasma concentration-time curve. 3 The mean bioavailability of oxytetracycline was greatest with preparations of the hydrochloride, and with film-coated tablets of the dihydrate. In contrast, sugar-coated tablets of oxytetracycline dihydrate were associated with poorer dissolution characteristics and reduced biological availability.     

Bioavailability study of two different verapamil formulations.

Relative bioavailability and bioequivalence of two oral verapamil preparations were investigated (dosage 80 mg, film-coated tablets as reference, dragées as test formulation). The clinical study was performed in a 2-period-cross-over design with 16 male healthy volunteers (mean age 28.8 +/- 3 years). The active metabolite norverapamil was included in the investigation. To assess bioequivalence several pharmacokinetic characteristics (i.e. AUC(o-oo), Cmax, tmax) were taken into account. Shortest 90% confidence intervals were calculated based on parametric (ANOVA, ANOVAlog) and non-parametric (Wilcoxon, Mann-Whitney) statistical tests. A positive decision for bioequivalence was accepted if the confidence intervals did not exceed the limits of 80-120% for AUC and 70-130% for Cmax. A mean relative bioavailability of 127% for the test preparation was found. Thus, bioavailability of the dragées is marked higher than bioavailability of the film-coated tablets.     

枸橼酸钾溶液中枸橼酸钾含量测定方法的改进

目的改进枸橼酸钾溶液中枸橼酸钾含量测定方法。方法采用pH指示剂吸光度比值法,测定波长为431nm,547nm。结果线性关系良好,r=0.9991,平均回收率为99.82%,RSD=0.78%。与离子交换后的中和滴定法比较,测定结果差异无统计学意义。结论方法准确度高,简便,快速,适用于医院制剂的快速分析。     

Bioavailability investigation of two different oral formulations of doxepin

Two different oral doxepin (CAS 1668-195) formulations (Doxepin-ratiopharm 25 mg film-coated tablets as test preparation and 25 mg dragées of the reference preparation) were investigated in 30 healthy male and female volunteers in order to prove bioequivalence between these preparations. A single 75 mg oral dose (3 units of test or reference preparation) was given according to a randomised two-way cross-over design in the fasted state. Blood samples for determination of plasma concentration of doxepin and its metabolite N-desmethyldoxepin were collected at pre-defined time points up to 168 h following drug administration. A wash-out period of three weeks separated both treatment periods. Doxepin and N-desmethyldoxepin plasma concentrations were determined by means of a validated LC-MS/MS method. Values of 193,463 pgh/ml (test preparation) and 197,988 pg h/ml (reference preparation) for doxepin as well as values of 313,298 pg h/ml (test preparation) and 306,663 pgh/ml (reference preparation) for N-desmethyldoxepin for the parameter AUC0-infinity demonstrate a nearly identical extent of drug absorption. Maximum concentrations (Cmax) for doxepin/N-desmethyldoxepin of 15,960.06/6,883.69 pg/ml and 18,614.73/6,846.62 pg/ml were achieved for test and reference preparation. Time to reach doxepin maximum plasma concentration (tmax) was 1.98 h for both preparations and for N-desmethyldoxepin tmax was 4.52 h (test preparation) and 4.15 h (reference preparation). Cmax and AUC0-infinity values were tested for statistically significant differences by means of the Two One-Sided T-Tests procedure following ln-transformation of data. Bioequivalence was assumed if the 90% confidence intervals of the T/R-ratios were in the range of 80%-125% for ln-transformed AUC0-infinity and 70%-143% for ln-transformed Cmax. Based on the results obtained in this study, bioequivalence between the test and the reference preparation was demonstrated.     

Bioavailability investigation of two different oral formulations of methylprednisolone

Two different oral methylprednisolone (CAS 83-43-2) formulations (Methylprednisolon-ratiopharm 8 mg tables as test preparation (T) and tablets of a reference preparation (R)) were investigated in 16 healthy volunteers in order to prove bioequivalence between these preparations. A single 8 mg oral dose was given according to a randomised two-way crossover design in the fasted state. Blood samples for determination of methylprednisolone plasma concentrations were collected at pre-defined time points up to 16 h following drug administration. A washout period of 3 days separated both treatment periods. Methylprednisolone plasma concentrations were determined by means of a validated HPLC method. Values of 342.53 ng.h/ml (test preparation) and 336.61 ng.h/ml (reference preparation) for the parameter AUC0-infinity demonstrate an nearly identical extent of drug absorption. Maximum concentrations (Cmax) of 66.58 ng/ml and 70.51 ng/ml were achieved for test and reference preparation. Time to reach maximum plasma concentration (tmax) was 2.2 h for both preparations. Cmax and AUC0-infinity-values were tested parametrically by the two one-sided t-test procedure. Bioequivalence was concluded if the 90% confidence intervals of the T/R-ratios were in the range of 80-125% for AUC0-infinity and 70-143% for Cmax. Based on the results obtained in this study, bioequivalence between Methylprednisolone ratiopharm and the reference preparation was demonstrated.     

Bioavailability investigation of two different oral formulations of Tetrazepam

Two different oral tetrazepam (CAS 10379-14-3) formulations (Tetrazepam-ratiopharm film-coated tablets as test preparation and tablets of a reference preparation marketed in France) were investigated in 20 healthy volunteers in order to prove bioequivalence between these preparations. A single 50 mg oral dose was given according to a randomised two-way crossover design in the fasted state. Blood samples for determination of tetrazepam plasma concentrations were collected at pre-defined time points up to 96 h following drug administration. A washout period of 14 days separated both treatment periods. Tetrazepam plasma concentrations were determined by means of a validated LC-MS/MS method. Values of 3873.08 ngh/ml (test preparation) and 3930.69 ngh/ml (reference preparation) for the parameter AUC0-infinity demonstrate an nearly identical extent of drug absorption. Maximum concentrations (Cmax) of 482.08 ng/ml and 465.14 ng/ml were achieved for test and reference preparation. Time to reach maximum plasma concentration (tmax) was 1.39 hours for both preparations. Cmax and AUC0-infinity-values were tested parametrically by an analysis of variance (ANOVA). Bioequivalence was concluded if the 90% confidence intervals of the T/R-ratios were in the range of 80%-125% for AUC0-infinity and 70%-143% for Cmax. Based on the results obtained in this study, bioequivalence between the test and the reference preparation was demonstrated.     

Bioavailability of two preparations of furosemide and their pharmacological activity in normal volunteers

The relative bioavailability and diuretic effect of 2 commercially available tablet preparations of furosemide 40 mg was examined in 10 healthy male volunteers. A close linear relationship between the urinary excretion rate of furosemide and the rate of sodium ion excretion in urine and/or flow rate of urine was demonstrated. There were no significant differences in the urinary excretion of furosemide, sodium and potassium ions or urinary volume following the oral doses. The difference in drug content affected the urinary recovery of furosemide over 24 h but had no effect on the pharmacological response. The analytical power of ANOVA using the various parameters of the responses to furosemide was no lower than when the parameters of urinary excretion of furosemide were used.     

Bioavailability of four ursodeoxycholic acid preparations

BACKGROUND: Ursodeoxycholic acid (UDCA) is the drug of choice for treating primary biliary cirrhosis and dissolving cholesterol gallstones. OBJECTIVES: The objective of this study was to compare the bioavailability of four commercially available ursodeoxycholic acid formulations in standardized doses. METHODS: Twenty-four healthy subjects were studied in groups of four, and received each of the different UDCA preparations in random order, with a 1-week washout or more in-between. Serum UDCA levels were determined for a 6-h period. The mean area under the curve (AUC), Cmax and Tmax were determined for each drug formulation, and the results compared. Dose proportionality was determined using the Canadian Ursofalk tablet using either 250 mg, 500 mg or 750 mg dosing. The intraparticipant variability was assessed by asking each participant to repeat the last drug that they took the second time, 1 week later. RESULTS: The mean AUC was 68.99 micromol/1.6 h-1 for the USA UDCA tablet, 59.34 micromol/1.6 h-1 for the Canadian UDCA tablet, 55.55 micromol/1.6 h-1 for Ursolvan capsules, and 46.66 micromol/1.6 h-1 for Actigall capsules. The mean Cmax values were 24.29, 17.85, 16.63 and 413.32 nmol/mL, respectively. The mean Tmax was 1.82, 2.3, 2.79 and 3.39 h, respectively. Linear aggression analysis assessing the direct proportionality of AUC on the dose for the Canadian UDCA tablet gave an estimate of 0.063 + 0.0164 (standard error, P-value=0.0117), e.g. if the dose increases from 250 mg to 500 mg, the serum ursodeoxycholic acid increases by 250 x 0.063=15.75. There was excellent reproducibility for the AUC for the North American tablets (0.97, 0.88) compared to the two capsules (0.32, 0.15). CONCLUSIONS: The significantly higher AUC and Cmax and shorter Tmax for the Canadian Ursofalk tablets compared to the UDCA capsule preparations supports better bioavailability.     

Comparative studies on the bioavailability of nicergoline from two different steady-state preparations]

Comparative Studies on the Bioavailability of Nicergoline from Two Different Preparations in Steady State The bioavailability of nicergoline (CAS 27848-84-6) in a new 30 mg tablet and a 10 mg dragee formulation (Sermion) was evaluated under steady state conditions in 18 healthy male volunteers between the age of 21 and 37 years. During the run-in phase, the volunteers received on 7 consecutive days 30 mg nicergoline either 1 x 30 mg/d tablet (test substance) or 3 x 10 mg dragees (reference). On day 8, after intake of 1 x 30 mg in a 24 h interval or 1 x 10 mg in a 8 h interval respectively, the plasma concentrations of the nicergoline metabolite 10-methoxy-6-methyl-ergoline-8 beta-methanol (MDL) were measured. The area under the plasma concentrations in the 24 h interval after administering the 30 mg tablet was not 3 times greater as to be expected; it was by a factor of 4 significantly greater than the area under the curve of the 10 mg dragee in the 8 h interval. Therefore, nicergoline has a higher availability in the 30 mg tablet than in the 10 mg dragee form. Both formulations were equally well tolerated.     

2种国产司帕沙星制剂的生物等效性研究

目的 建立反相高效液相色谱法测定血浆中司帕沙星浓度，并研究其片剂与胶囊的人体相对生物利用度。方法 采用随机交叉、自身对照试验设计，20例健康男性志愿受试者单剂口服国产司帕沙星片剂或胶囊剂400mg后在不同时间点采血。用反相高效液相色谱法测定血清中司帕沙星浓度，以方差分析对主要药动学参数进行差别检验，双单侧t检验进行生物等效性判定。结果单剂量口服用400mg司帕沙星胶囊剂和片剂后的药物动力学参数AUC0～96分别为（50．50±6．78）和（50．82±11．57）μg·h·mL^-1，AUC0～∞。分别为（53．44±7．79）和（54．25±12．96）μg·h·mL^-1、tmax分别为（4．22±1．59）和（5．06±2．13）h、Cmax别为（1．46±0．23）和（1．46±0．31）μg·h·mL^-1、t1／2分别为（22．03±4．57）和（23．01±2．94）h。胶囊剂和片剂的相对生物利用度为102．41％±16．77％。2种制剂的药物动力学参数无明显差异。结论RP-HPLC法能快速、准确地测定人血浆中的司帕沙星，受试制剂与参比制剂具有生物等效性。