Bioequivalence study of two enalapril maleate tablet formulations in healthy male volunteers. Pharmacokinetic versus pharmacodynamic approach

Male Breast Cancer as a Second Primary Cancer: Increased Risk Following Lymphoma

BACKGROUND

Male breast cancer (MBC) as a second primary cancer (SPC) has a known association with prior MBC. However, its association with non-breast index malignancies, relative to population risk, has not been previously reported.

MATERIALS AND METHODS

Using Surveillance, Epidemiology, and End Results program (9 catchment area) data, we identified MBCs diagnosed from 1973-2012 as their SPC. Information regarding the index malignancy was also obtained. Standardized incidence ratios (SIR) of MBC as SPC were estimated, along with incidence rates and trends. Kaplan-Meier curves were used to estimate survival.

RESULTS

Over a 38-year period, 464 MBCs were identified as SPC. The most common index malignancies were breast (SIR 30.86, 95% confidence interval [CI] 21.50-42.92, p < .001), lymphoma (SIR 1.58, 95% CI 1.08-2.22, p = .014), melanoma (SIR 1.26, 95% CI 0.80-1.89), urinary (SIR 1.05, 95% CI 0.74-1.43), colorectal (SIR 0.94, 95% CI 0.69-1.24), and prostate (SIR 0.93 95% CI 0.81-1.07). Apart from the known association with prior breast cancer, the only significant association was with lymphoma as an index cancer, although not significant with a Bonferroni correction. From 1975-2012, incidence of breast cancer as a first cancer increased at an annual percentage change of 1.3% while breast cancer as a SPC increased at 4.7% (both p values < .001).

CONCLUSION

Male breast cancer as a SPC has increased markedly over 4 decades. Men with a history of lymphoma may experience higher-than-expected rates of breast SPC. These observations warrant further research, and suggest possible etiologic connections with disease biology, prior therapy, or genetics.

IMPLICATIONS FOR PRACTICE

This study reports that men are presenting more frequently to the clinic with breast cancer, both as an initial cancer and as a second cancer following an earlier malignancy. We also report the novel observation that men who survive lymphoma are at increased risk of developing a subsequent breast cancer. Further work is needed to better understand possible treatment or biologic causes of this association. More immediately, these findings suggest the need for heightened vigilance for male breast cancer overall and, in particular, for male lymphoma survivors.

Biowaiver Monographs for Immediate-Release Solid Oral Dosage Forms: Enalapril

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence testing for the marketing authorization of immediate-release, solid oral dosage forms containing enalapril maleate are reviewed. Enalapril, a prodrug, is hydrolyzed by carboxylesterases to the active angiotensin-converting enzyme inhibitor enalaprilat. Enalapril as the maleate salt is shown to be highly soluble, but only 60%-70% of an orally administered dose of enalapril is absorbed from the gastrointestinal tract into the enterocytes. Consequently, enalapril maleate is a Biopharmaceutics Classification System class III substance. Because in situ conversion of the maleate salt to the sodium salt is sometimes used in production of the finished drug product, not every enalapril maleate-labeled finished product actually contains the maleate salt. Enalapril is not considered to have a narrow therapeutic index. With this background, a biowaiver-based approval procedure for new generic products or after major revisions to existing products is deemed acceptable, provided the in vitro dissolution of both test and reference preparation is very rapid (at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Additionally, the test and reference product must contain the identical active drug ingredient.

Bioequivalence study of two formulations of enalapril, at a single oral dose of 20 mg (tablets): A randomized, two-way, open-label, crossover study in healthy volunteers

BACKGROUND

Enalapril maleate is the monoethyl ester prodrug of enalapril- at, an angiotensin-converting enzyme inhibitor indicated in the management of essential and renovascular hypertension, and in the treatment of congestive heart failure and in asymptomatic patients with left ventricular dysfunction and an ejection fraction of ≥35%. Enalapril has little pharmacologic activity until hydrolyzed in vivo to enalaprilat.

OBJECTIVE

The aim of the present study was to compare the bioavailability and tolerability of 2 commercial brands (test and reference formulations) of enalapril tablets (20 mg), described as the rate and extent of absorption of the active moiety, to assess their bioequivalence.

METHODS

This single-dose, randomized, 2-way, open-label, crossover study in healthy volunteers aged 18 to 40 years was conducted at the Clinical Pharmacology Study Unit, Hospital Clínico San Carlos (Madrid, Spain). Subjects were randomized to receive (under fasting conditions) either the test or reference formulation of enalapril (20-mg tablet) at study period 1 and the opposite formulation at study period 2. Study periods were separated by a washout period of at least 7 days. During each study period, 15 plasma extractions were made to determine enalapril and enalaprilat plasma concentrations and to calculate the pharmacokinetic (PK) properties (maximal plasma drug concentration [Cmax], time to Cmax [Tmax], area under the plasma concentration-time curve [AUC] to the last measurable concentration [AUCt], AUC from time 0 to infinity [AUC0-∞], mean residence time, and elimination half-life [tl2]) of both. Physical examination, subject interview, laboratory analyses, electrocardiogram, and blood pressure (BP) were used to assess tolerability.

RESULTS

Twenty-four subjects were included in the study (12 men, 12 women; mean [SD] age, 22.8 [2.2] years [range, 19-30 years]). Of these, 1 subject (4.2%) withdrew from the study for personal reasons; thus, PK and statistical analyses included results from 23 subjects. No statistically significant sequence or period effect was found. Tmax was not statistically different between the 2 formulations, and the 90% CI calculated for Tmax for the difference of the medians was within the predefined range. The 90% CIs of the logarithmically transformed concentration-derived parameters (Cmax AUCt, and AUC0-∞) also were within the predefined range; thus, the 2 formulations are considered bioequivalent. For both formulations, systolic and diastolic BPs showed significant reductions compared with baseline values (P < 0.05). Seven adverse effects were recorded, all of them transient and none of severe intensity.

CONCLUSIONS

In this study of 2 commercial brands (test and reference formulations) of enalapril in healthy subjects, designed and conducted under Good Clinical Practice guidelines, a similar rate and extent of absorption for both formulations were found to be bioequivalent. Both formulations produced a significant decrease in BP values and were generally well tolerated.

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using solid phase extraction for the simultaneous determination of plasma concentrations of enalapril and enalaprilate in hypertensive patients treated with different pharmaceutical formulations

Enalapril maleate, available on the market in a variety of different pharmaceutical formulations, is commonly used for the control of systemic arterial hypertension. Many therapeutical failures have been reported thus far in clinical practice with respect to switching between different pharmaceutical formulations of the same product during pharmacological therapy. In the present study, plasma concentrations of enalapril and enalaprilate were measured in hypertensive patients undergoing treatment with different pharmaceutical formulations.

MATERIALS AND METHODS

Pharmaceutical formulations studied included the reference brand product, a generic formulation, and a third drug product marketed as "similar"; plasma samples were obtained from 30 hypertensive volunteer patients. Drug was extracted from the plasma by solid phase extraction and determined by liquid chromatography-tandem mass spectrometry. The method was validated for the main analytical parameters.

RESULTS

The analytical method developed in this study, using liquid chromatography-tandem mass spectrometry, was confirmed as suitable for application in the determination of plasma concentrations in patients and subsequently revealed statistically significant differences in plasma concentrations between the 3 treatment groups.

CONCLUSIONS

Such differences reinforce the hypothesis that the bioequivalence tests currently proposed by the regulatory authorities to promote interchangeability between pharmaceutical formulations may not in fact represent a definitive parameter for guaranteeing similar plasma concentrations.

PHARMACOKINETICS AND PHARMACODYNAMICS OF A NITRIC OXIDE-RELEASING DERIVATIVE OF ENALAPRIL IN MALE BEAGLES

1. Pharmacological compounds that release nitric oxide (NO) have been useful tools in the evaluation of the broad role of NO in physiopathology and therapeutics. The present study compared the pharmacokinetics and pharmacodynamics of enalapril and an NO-releasing enalapril molecule (NCX899) in conscious male beagles. The effects of both enalapril and NCX899 in the arterial hypertension and bradycardia induced by acute NO inhibition in anaesthetized dogs were also investigated. 2. Dogs received either NCX899 (4 micromol/kg, i.v.) or enalapril (4 micromol/kg, i.v.), after which plasma concentrations of the analytes and metabolites were quantified by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). 3. In the NCX899 group, the area under the time-course curve (AUC(0-24h)) was 29.18 +/- 4.72, 229.37 +/- 51.32 and 5159.23 +/- 514.88 microg.h/L for the analytes nitro-enalapril, enalapril and enalaprilat, respectively. In the enalapril group, the AUC(0-24h) was 704.53 +/- 158.86 and 4149.27 +/- 847.30 microg.h/L for the analytes enalapril and enalaprilat, respectively. Statistical analysis of data from both groups showed a significant difference for the analyte enalapril, but not for enalaprilat. Moreover, NCX899 and enalapril were equally effective in inhibiting the activity of serum angiotensin-converting enzyme. 4. In anaesthetized dogs, i.v. administration of the NO synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME; 0.1-10 mg/kg) significantly elevated arterial blood pressure, with concomitant bradycardia. The compound NCX899 significantly attenuated both arterial hypertension and bradycardia, whereas enalapril had no significant effect. 5. In conclusion, the present results showed that the NO-releasing derivative of enalapril NCX899 presents a pharmacokinetic/pharmacodynamic relationship similar to its parent compound enalapril. Moreover, NCX899 (but not enalapril) was effective in protecting against the cardiovascular changes induced by acute NOS inhibition.

High-performance liquid chromatographic determination of enalapril in human plasma by enzyme kinetic analytical method

A high-performance liquid chromatographic method for indirect determination of enalapril in human plasma, was developed and validated. An exogenous angiotensin converting enzyme after drug inhibition was determined by reacting with hippuryl-histidyl-leucine to produce hippuric acid (HA) which was inversely proportional to the amount of enalaprilat in plasma. The HPLC was carried out on a Lichrosphere 60RP-select B, C18, 5 microm (125 mm x 4.0 mm i.d.) column at flow rate of 1.0 ml/min. The analysis time per injection was within 6.5 min. The lowest concentration of enalaprilat to be quantitated was 3.0 ng/ml with the acceptable accuracy and precision. This successfully developed method was practically and accurately used for pharmacokinetics and bioequivalent study of enalapril.

Lisinopril quantification in human plasma by liquid chromatography–electrospray tandem mass spectrometry

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection was developed for the determination of Lisinopril in human plasma using Enalaprilat as internal standard. The analyte and internal standard were extracted from the plasma samples by solid-phase extraction using Waters HLB Oasis SPE cartridges and chromatographed on a C8 analytical column. The mobile phase consisted of acetonitrile/water (60:40, v/v) + 20 mM acetic acid + 4.3 mM of triethylamine. The method had a chromatographic total run-time of 6.5 min and was linear within the range 2.00-200 ng/ml. Detection was carried out on a Micromass triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM). The precision (CV%) and accuracy, calculated from limit of quantification (LOQ) samples (n = 8), were 8.9 and 98.9%, respectively. The method herein described was employed in a bioequivalence study of two tablet formulations of Lisinopril 20mg.

Bioequivalence evaluation of two brands of enalapril 20mg tablets (narapril andrenitec) in healthy human volunteers

The bioequivalence of two brands of enalapril 20 mg tablets was demonstrated in 24 healthy human volunteers after a single oral dose in a randomized cross-over study, conducted at IPRC, Amman, Jordan. Reference (Renitec, MSD, Netherlands) and test (Narapril, Julphar, UAE) products were administered to fasted male volunteers; blood samples were collected at specified time intervals, plasma separated and analysed for enalapril and its active metabolite (enalaprilat) using a validated LC-MS/MS method at Cartesius Analytical Unit, Institute of Biomedical Sciences, USP, Sao Paulo, Brazil. The pharmacokinetic parameters AUC(0-t), AUC(0-infinity), Cmax, Tmax, T(1/2) and elimination rate constant were determined from plasma concentration-time profile for both formulations and were compared statistically to evaluate bioequivalence between the two brands, using the statistical modules recommended by FDA. The analysis of variance (ANOVA) did not show any significant difference between the two formulations and 90% confidence intervals fell within the acceptable range for bioequivalence. Based on these statistical inferences it was concluded that the two brands exhibited comparable pharmacokinetic profiles and that Julphar's Narapril is bioequivalent to Renitec of MSD, Netherlands.

Relationship of serum ACE inhibition to oral dose of enalapril in normotensive volunteers

OBJECTIVES

To determine the relationship between oral dose of enalapril and parameters describing serum angiotensin converting enzyme (ACE) inhibition.

METHODS

Four different oral doses of enalapril maleate (2.5, 5, 10 and 20 mg) were administered to six healthy normotensive volunteers, in a four-period crossover study. Serum ACE inhibition profiles were determined in each case using a synthetic substrate, hippuryl-histidyl-leucine (HHL). Pharmacodynamic parameters of the drug (Emax and AUEC0-->24) were calculated and their relationship to oral doses investigated using linear regression analysis.

RESULTS

There was no significant relationship between drug dose and the two pharmacodynamic parameters (Emax and AUEC0-->24). The r2 values were 0.548 (F=3.63, P=0.153) and 0.6360 (F=5.24, P=0.106) for Emax and AUEC0-->24, respectively.

CONCLUSION

The extent of serum ACE inhibition, as the main determinant of the blood pressure lowering effect of enalapril, is not dose-dependent within the single dose range of 2.5-20 mg.

Determination of enzyme (angiotensin convertase) inhibitors based on enzymatic reaction followed by HPLC

For determination of levels of plasmatic inhibitor of ACE (angiotensin convertase) a simple method was used based on a combination of enzymatic reaction followed by an HPLC determination of its product. The inhibitor (e.g. enalaprilat) was at first separated from the biological material by deproteination (methanol). Then, an aliquot of the sample was added to the reaction mixture containing a commercial ACE enzyme, its specific substrate FAPGG (N-(3-[2-furyl]acryloyl)-Phe-Gly-Gly) and buffer (Tris--HCl, pH 7.5). Degree of inhibition of the conversion of this substrate to FAP (desGlyGlyFAPGG) by the inhibitor present in the sample is related to its amount by a simple dose-response relationship. The amount of the FAP was determined by an HPLC on a RP-18 column with an acetonitril--nonylamine buffer (pH 2.4, adjusted with phosphoric acid) as a mobile phase with detection at 305 nm. Alternatively, the activity of the endogenous ACE present in the plasma was measured. The substrate FAPGG was added to the plasmatic sample containing both the inhibitor and endogenous ACE (as the sample was not deproteinized in this case) and the reaction product was determined as above. Inhibitor concentration has been obtained from a dose--response curve expressing the interaction with inhibitor with an ACE enzyme.

Quantification of pulmonary capillary endothelium-bound angiotensin converting enzyme inhibition in man

Angiotensin converting enzyme (ACE, kininase II) is an endothelial luminal ectoenzyme expressed abundantly on the pulmonary capillary endothelium and recognized as the site for the conversion of circulating angiotensin I to II. In the present study, we have applied recently developed methodologies for assaying pulmonary capillary endothelium-bound (PCEB) ACE activity in man, to estimate the interaction of an ACE inhibitor (enalaprilat) with PCEB ACE in human subjects. Trace amounts of the specific ACE substrate, 3H-benzoyl-Phe-Ala-Pro (3H-BPAP; 40 Ci or 2 nmol), was injected as a bolus into the subclavian vein and immediately blood was withdrawn from a radial arterial catheter. Plasma concentrations of surviving substrate and product (3H-benzoyl-Phe) were estimated and BPAP utilization was calculated during a single transpulmonary passage, at baseline (T(0)) and at 15 min (T(15)) and 2 h (T(120)) after intravenous administration of 1.5 g/kg enalaprilat in 12 normotensive subjects. This treatment had no significant effect on mean arterial pressure (91+/- 6 vs. 84 +/- 7 vs. 88 +/- 6 mm Hg for T(0), T(15) and T(120), respectively), but significantly decreased serum and PCEB ACE activities. When normalized to predrug (T(0)) activity levels, enalaprilat inhibited PCEB and serum ACE activities at T(15) 74 +/- 6% and 68 +/- 6%, respectively. However, 2 h after enalaprilat (T(120)), PCEB ACE inhibition was maintained at 66 +/- 7%, whereas serum ACE inhibition was reduced to 46 +/- 8% (P<.01 from PCEB ACE), suggesting a preferential PCEB ACE inhibitory effect of enalaprilat.