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Nenad Sarapa

Publications and source records attributed to Nenad Sarapa.

8 recordsLinked to original sources
PubMed2006

Implications of methodological differences in digital electrocardiogram interval measurement.

Well-specified recommendations have yet to be established on how electrocardiogram (ECG) interval measurement should be performed by digital on-screen caliper systems to assess drug-induced effect on cardiac repolarization in pharmaceutical clinical trials with adequate precision and reproducibility. Since 1997, the industry has followed the European Committee for Proprietary Medicinal Products Points to Consider by using fully manual measurement of 3 consecutive sinus rhythm PQRST complexes in 1 lead only (typically limb lead II). More recently, semiautomatic measurement performed on representative (median) beats and based on the global leads has been considered. The International Conference on Harmonization E14 guidance (June 2005) advocates development of quality standards for centralized ECG interval measurement and allows all methods "whether or not assisted by computer" but includes no recommendations on how to perform the measurement. We provide an overview of the currently available methods for digital ECG interval measurement and the implications of between-method differences on quality of ECG interval measurements. We applied 4 methods most commonly used to assess QT prolongation (applied on 3 raw beats in limb lead II or by global measurement on 1 or 12 superimposed representative beats). QT, QTc Fridericia, and RR interval durations were measured on resting 12-lead digital ECGs obtained in 26 healthy volunteers predose and at 1, 2, and 3 hours after dosing with a single 160 mg oral dose of sotalol. Absolute interval durations and changes from baseline were compared between the 4 measurement methods. A better understanding of the implications from different measurement methodologies will facilitate more informed choice of the appropriate method for ECG interval measurement on clinical trials.

Algorithms↗
PubMed2005

The effect of mild and moderate hepatic impairment on the pharmacokinetics of valdecoxib, a selective COX-2 inhibitor.

PURPOSE: This study evaluated the effects of varying degrees of hepatic impairment on the pharmacokinetics and safety of valdecoxib following single and multiple dosing. METHODS: This was an open-label, randomised, parallel group study in 12 subjects with mild hepatic impairment (Child-Pugh Class A) and in 13 with moderate hepatic impairment (Child-Pugh Class B) matched for age, weight, sex, and smoking status; there were two control groups of 12 healthy volunteers, one for each study group. All subjects received a single dose of valdecoxib 20 mg on day 1 and valdecoxib 20 mg twice daily on days 4-7, followed by a single morning dose on day 8. Plasma concentrations of free (unbound) and total valdecoxib and its active hydroxylated metabolite (SC-66905) were measured following single and multiple dosing (day 1 and day 8). Additionally, all subjects received a single intravenous dose of lidocaine 60 mg during the pretreatment period to determine plasma concentrations of monoethylglycinexylidide (MEGX) as a marker of hepatic CYP3A4 activity. RESULTS: The mean apparent oral clearance of free valdecoxib in plasma at steady state decreased by 22-25% in those with mild to moderate impairment (corresponding to a 28-33% increase in the AUC of free valdecoxib and a 19-23% decrease in the AUC of total SC-66905). The mean free fraction of valdecoxib in plasma increased by 9-38%, resulting in a mean decrease in apparent oral clearance of total valdecoxib in plasma of 0-15% (corresponding to a 0-17% increase in the AUC of total valdecoxib). Individual AUCs for free valdecoxib and total SC-66905 did not correlate well with AUCs for MEGX, indicating that decreases in intrinsic clearance of valdecoxib in those with hepatic impairment could not solely be explained by decreased CYP3A4 expression in hepatic impairment. CONCLUSIONS: In our small study sample, mild and moderate hepatic impairment appeared to have only a modest effect on valdecoxib and SC-66905 pharmacokinetics. The adjustment of valdecoxib dose or dosing regimen does not appear mandatory in subjects with mild or moderate hepatic impairment, although caution is necessary during treatment of these patients with valdecoxib.

Adult↗
PubMed2005

The application of accelerator mass spectrometry to absolute bioavailability studies in humans: simultaneous administration of an intravenous microdose of 14C-nelfinavir mesylate solution and oral nelfinavir to healthy volunteers.

The absolute bioavailability of nelfinavir was determined in 6 healthy volunteers following simultaneous administration of 1250 mg oral nelfinavir and an intravenous infusion of (14)C-nelfinavir mesylate on day 1 and at steady state. Nelfinavir oral bioavailability decreased from 0.88 to 0.47 over the 11-day study period. The moderate bioavailability of nelfinavir was due to significant first-pass metabolism rather than low absorption, limiting the potential of formulation improvement to decrease pill burden. Human absolute bioavailability studies with accelerator mass spectrometry microdosing, in which an intravenous microdose is given along with a conventional oral dose of the same drug, can differentiate between gastrointestinal absorption and the first-pass metabolism of new drug candidates. Accelerator mass spectrometry allowed a several thousand-fold dose reduction of (14)C-nelfinavir relative to that required for liquid scintillation counting. Accelerator mass spectrometry microdosing reduces potential safety issues around dosing radioactivity to humans and prevents the need to formulate high intravenous doses.

Administration, Oral↗
PubMed2004

Electrocardiographic identification of drug-induced QT prolongation: assessment by different recording and measurement methods.

BACKGROUND: Careful assessment of QT interval prolongation is required before novel drugs are approved by regulatory authorities. The choice of the most appropriate method of electrocardiogram (ECG) acquisition and QT/RR interval measurement in clinical trials requires better understanding of the differences among currently available approaches. This study compared standard and Holter-derived 12-lead ECGs for utility in detecting sotalol-induced QT/QTc and RR changes. Manual methods (digitizing pad and digital on-screen calipers) were compared for precision of QT and RR interval measurement. METHODS AND RESULTS: Sixteen hundred pairs of serial 12-lead digital ECGs were recorded simultaneously by standard resting ECG device and by continuous 12-lead digital Holter over 3 days in 39 healthy male and female volunteers. No therapy was given on the 1st day followed by 160 mg and 320 mg of sotalol on the 2nd and 3rd day, respectively. Holter-derived and standard ECGs produced nearly identical sotalol-induced QT/QTc and RR changes from baseline, as did the manual digipad and on-screen caliper measurements. The variability of on-screen QT measurement in this study was greater than that of digipad. CONCLUSIONS: Digital 12-lead Holter and standard 12-lead ECG recorders, as well as the manual digitizing pad and digital on-screen calipers, are of equal utility for the assessment of drug-induced change from baseline in QT and RR interval, although the variability of the on-screen method in this study was greater than of the digipad.

Electrocardiography↗
PubMed2003

Assessment of normal and tumor tissue uptake of MAG-CPT, a polymer-bound prodrug of camptothecin, in patients undergoing elective surgery for colorectal carcinoma.

PURPOSE: MAG-camptothecin (MAG-CPT) is the lead compound of a novel drug delivery system in which an active cytotoxic moiety, camptothecin (CPT), is covalently linked to a soluble polymeric carrier (MAG) to form an inactive prodrug. The mechanism of action of CPT remains unaltered, but the delivery system is thought to allow the carrier-bound drug to accumulate in tumor tissues and release the active CPT locally. This proof-of-concept clinical study was designed to determine whether MAG-CPT was preferentially delivered to or retained in tumor tissue compared to adjacent normal tissue or plasma, and to estimate the degree of intratissue release of CPT. METHODS: This was an open, non-randomized study in ten adult patients scheduled for elective surgery for colorectal cancer. Patients received a single dose of 60 mg/m2 (CPT equivalent) of MAG-CPT 24 h, 3 days or 7 days prior to surgery. Plasma, tumor, and adjacent normal tissue samples were collected simultaneously at the time of surgery and analyzed for MAG-bound and released CPT concentrations. RESULTS: MAG-bound and free CPT concentrations in plasma, tumor, and normal tissue achieved equilibrium by 24 h after dosing, declining in parallel up to 7 days after dosing. MAG-bound CPT was delivered to similar levels to tumor and normal tissue. At 24 h after dosing, the mean+/-SD MAG-bound CPT concentrations were 861+/-216 ng/g in tumor and 751+/-215 ng/g in adjacent normal tissue, and free CPT concentrations were lower in tumor than in normal tissue (12.2+/-4.7 ng/g and 21.9+/-6.7 ng/g, respectively). At 24 h after dosing, mean+/-SD ratios of MAG-bound and free CPT in tumor and plasma were 0.13+/-0.03 and 0.22+/-0.09, respectively, and the ratios did not change for up to 7 days after dosing, indicating a lack of preferential retention of MAG-bound CPT or release of free CPT in tumor. These results are in marked contrast to previous data from animal tumor xenograft studies, where MAG-CPT levels were higher in tissue than in plasma at 3 and 7 days after a single i.v. dose. CONCLUSIONS: Delivery of CPT to the target tumor tissue is achievable by means of the MAG-CPT polymer-bound delivery system, with the equilibrium between plasma and tumor tissue concentrations of released CPT being established within 24 h after dosing. However, preferential retention of MAG-bound or released CPT in the tumor relative to normal tissue or plasma was not detected during the 7 days after dosing. The methods employed in our study could be of use in making "go/no-go" decisions on further development of anticancer drugs.

Acrylamides↗
PubMed2003

Identification of sotalol-induced changes in repolarization with T wave area-based repolarization duration parameters.

In this study, we investigated the validity of T wave area-based parameters for the identification of drug-induced changes of repolarization. Based on electrocardiograms from 39 healthy patients, we computed the stability of repolarization measurements and compared the sotalol-induced repolarization changes when measured with area-based parameters and traditional QT interval techniques (manual and automatic). Also, we evaluated the effect of different types of heart rate correction on these repolarization measurements. The results show that the stability of the automatic repolarization measurements is higher when measured using computer algorithm than using manual QT measurement. By using a population-based heart rate correction, the area-based parameters reveal significant modification of the overall shape of the T wave in its early, middle, and final part. In conclusion, morphological parameters of T wave are able to identify the changes in repolarization interval induced by sotalol. These parameters are more stable and thus more reliable than the traditional QT interval measurements.

Electrocardiography↗
PubMed2003

Valdecoxib, a COX-2-specific inhibitor, does not affect cardiac repolarization.

This double-blind, four-way crossover study assessed the effect of valdecoxib on the QTc interval duration in 25 male and 9 female healthy adults. Subjects received placebo or 40 mg, 80 mg, or 120 mg valdecoxib once daily for 5 days. Serial ECGs were obtained for 24 hours before the first treatment (baseline) and on the 5th day of each treatment. The study was statistically powered to detect a difference of > or = 5.6 ms in the average daily QTc change from baseline and a > or = 7.8-ms difference in the average maximal daily change from baseline. No QTc prolongation versus placebo (Fridericia's or Bazett's correction) was observed for any valdecoxib dose. A 22% greater than proportional increase in valdecoxib AUC0-24 was observed over the 40- to 120-mg dose range, supporting the conclusiveness of the negative QTc risk assessment even at supratherapeutic doses (up to three times the maximum recommended dose of 40 mg per day) and concentrations. In conclusion, repeated administration of doses up to 120 mg valdecoxib had no effect on cardiac repolarization in healthy volunteers, suggesting that chronic administration of valdecoxib to patients would not increase the risk from cardiac arrhythmia associated with QT prolongation.

Adult↗