Does Circadian Rhythm Affect the Pharmacokinetics of Once-Daily Tobramycin in Adults With Cystic Fibrosis?

BACKGROUND: In the era of multiple daily dosing of systemic aminoglycosides, a circadian rhythm in the clearance of these vital antibiotics has been demonstrated in animals and healthy volunteers. Over the past decade, once-daily dosing regimens have been proved to be less nephrotoxic and were therefore adopted worldwide for most indications requiring treatment with an aminoglycoside. In this study, the effect of the time of administration on the pharmacokinetics of once-daily tobramycin in adults with cystic fibrosis (CF) experiencing a pulmonary exacerbation was investigated. METHODS: In this open randomized study, patients with CF received intravenous tobramycin at 8:00 or 22:00 hours. Pharmacokinetic and kidney function parameters were compared between the 2 groups. RESULTS: Twenty-five patients were included. The mean weight-corrected clearances of tobramycin were 1.46 versus 1.43 mL/h*kg (P = 0.50) and mean volumes of distribution were 0.25 versus 0.27 L/kg (P = 0.54) for the 8:00 and 22:00 groups, respectively. In addition, no significant differences were detected in changes in estimated clearances of creatinine or tobramycin on day 1 and day 8 in the 8:00 or 22:00 group, indicating that there was no decline in clearance over time. At day 8 of therapy, the increase in serum blood urea nitrogen in the 22:00 group was significantly higher than that in the 8:00 group (1.8 versus 0.2 mmol/L, P = 0.015). CONCLUSIONS: The time of administration (8:00 versus 22:00) did not affect tobramycin pharmacokinetics in the adult CF population studied. The increase in serum blood urea nitrogen in the 22:00 group requires further investigation.

A Novel Ileocolonic Release Peppermint Oil Capsule for Treatment of Irritable Bowel Syndrome: A Phase I Study in Healthy Volunteers.

INTRODUCTION: Peppermint oil (PO) has been shown to reduce abdominal pain in patients with irritable bowel syndrome (IBS). PO is assumed to induce intestinal smooth muscle relaxation and desensitization of nociceptive nerve afferents. To increase colonic PO concentration, an ileocolonic release peppermint oil (IC-PO) capsule has been developed. The aim of this study was to compare pharmacokinetic parameters of the currently available small intestinal release PO (SI-PO) and the novel IC-PO. METHODS: In this randomized, double-blind, crossover study, subjects received 182 mg of either SI-PO or IC-PO in a crossover design with a washout period of more than 14 days. Blood samples were collected to determine menthol glucuronide concentrations. RESULTS: Eight healthy volunteers (50% female, median age 22) were included. The time to reach the maximum concentration (Tmax) of IC-PO was significantly longer compared to SI-PO with a median (IQR) of 360 (360-405) versus 180 (120-180) min. The lag time (Tlag) was significantly longer with a median (IQR) of 225 (204-284) for IC-PO compared to 37 (6-65) min for SI-PO. The areas under the menthol glucuronide plasma concentration-time curves were significantly smaller with a median (IQR) of 2331 µg h/L (2006-2510) for IC-PO compared to 2623 µg h/L (2471-2920) for SI-PO. No significant differences were found in peak concentrations and elimination half-lives. CONCLUSION: IC-PO has a significantly delayed peak menthol glucuronide concentration and Tlag, both pointing to the release of PO in the more distal part of the intestine. This may enhance therapeutic efficacy as it results in increased exposure of colonic mucosal afferents to the PO. A randomized controlled trial investigating the efficacy of SI and IC-PO in IBS is currently ongoing. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02291445, EudraCT database 2014-004195-32.

Use of biguanides and the risk of colorectal cancer: a register-based cohort study.

Observational studies have shown conflicting results on the potential protecting effect of biguanide use with the risk of colorectal neoplasms. In addition, the cellular mechanism can either support or oppose biguanides influence on colorectal carcinoma. Our objective was to evaluate the association between biguanide use and colorectal carcinoma. A population-based cohort study using healthcare data from the Danish National database (1996-2007), was conducted. Oral antidiabetic drug users (n = 177,281) were matched 1:3 with a population-based reference group. Cox proportional hazard models estimated hazard ratios (HRs) of colorectal carcinoma. Stratification was performed to analyse the risk of colorectal cancer in current biguanide users. Two sub-analyses were performed, to investigate the risk of colorectal cancer associated with discontinuous and prolonged use of biguanides. Instead of a protective effect, we found that current biguanide users had a 1.2-fold increased risk of colorectal cancer (HR = 1.19, 95% CI = 1.08-1.30) as compared with the non-diabetes reference group. Prolonged use was not inversely associated with colorectal cancer either. When studying colorectal risk with biguanides, the underlying T2DM should be taken into account since a 1.3-1.6-fold increased risk was found in oral antidiabetic drug users compared to controls unexposed to diabetic medication. This study could not detect a protective effect of biguanide use with colorectal cancer. Therefore, this study does not support a further investigation of the effectiveness of biguanides to prevent colorectal carcinoma in clinical studies.

Optimal sampling strategy development methodology using maximum a posteriori Bayesian estimation.

Maximum a posteriori Bayesian (MAPB) pharmacokinetic parameter estimation is an accurate and flexible method of estimating individual pharmacokinetic parameters using individual blood concentrations and prior information. In the past decade, many studies have developed optimal sampling strategies to estimate pharmacokinetic parameters as accurately as possible using either multiple regression analysis or MAPB estimation. This has been done for many drugs, especially immunosuppressants and anticancer agents. Methods of development for optimal sampling strategies (OSS) are diverse and heterogeneous. This review provides a comprehensive overview of OSS development methodology using MAPB pharmacokinetic parameter estimation, determines the transferability of published OSSs, and compares sampling strategies determined by MAPB estimation and multiple regression analysis. OSS development has the following components: 1) prior distributions; 2) reference value determination; 3) optimal sampling time identification; and 4) validation of the OSS. Published OSSs often lack all data necessary for the OSS to be clinically transferable. MAPB estimation is similar to multiple regression analysis in terms of predictive performance but superior in flexibility.

Pharmacokinetics, analgesic effect, and tolerability of a single preprocedural dose of intranasal fentanyl in patients undergoing drain removal after breast reduction or augmentation surgery: A prospective, randomized, double-blind, placebo-controlled study.

BACKGROUND: Although acetaminophen is used to reduce pain after breast reduction or augmentation surgery, pain during the removal of the surgical drains is typically not specifically treated. Intranasally administered fentanyl may be suitable for pain control during removal of drains. The reported therapeutic window of fentanyl is between 0.2 and 1.2 ng/mL. OBJECTIVE: The aim of this study was to evaluate the analgesic effect, tolerability, and pharmacokinetics of a single preprocedural dose of intranasal fentanyl administered before removal of surgical drains in patients who had undergone breast reduction or augmentation surgery. METHODS: This was a randomized, double-blind, prospective study in healthy women (American Society of Anesthesiologists physical status I or II) between the ages of 18 and 65 years who were scheduled to undergo removal of surgical drains 1 to 4 days after breast reduction or augmentation surgery. A single dose of fentanyl nasal spray 0.05 mg/0.1 mL or placebo (preserved normal saline) 0.1 mL was administered 10 minutes before removal of drains. Because drain removal is generally carried out without specific analgesia, no rescue medication was provided. Pain intensity was measured on a visual analog scale (VAS) from 0 = no pain at all to 100 = worst pain possible. Pain intensity was evaluated immediately before administration of study medication (t = 0), at the time of drain removal (t = 10), and at 15, 20, 25, 40, and 70 minutes after administration of study medication. Safety measures included oxygen saturation, respiratory rate, heart rate, and blood pressure. Local and systemic adverse events were elicited by direct questioning throughout the study. Blood samples for pharmacokinetic analysis were collected at baseline and at 5, 10, 15, 30, 60, and 120 minutes after administration of study medication. The population pharmacokinetic parameters of fentanyl were calculated according to a 1-compartment open model with an iterative 2-stage Bayesian fitting procedure. RESULTS: Thirty-six women were randomized to treatment, and 33 completed the study. Their mean (SD) age was 39.2 (13.0) years, and their mean weight was 68.9 (10.7) kg. Mean VAS scores at baseline were 14.8 (17.8) for the fentanyl group and 6.0 (9.7) for the placebo group (P = NS); at the time of drain removal, the corresponding VAS scores were 31.0 (20.6) and 33.8 (25.7) (P = NS). Analysis of a random-effects model with mean VAS scores as a function of time as the dependent variable indicated a significant difference in mean VAS scores between the fentanyl and placebo groups (P = 0.006). The overall incidence of adverse events was 39.4% (13/33). Among the 17 patients in the fentanyl group, 8 reported > or =1 adverse event; among the 16 patients in the placebo group, 9 reported > or =1 adverse event. A mean estimated C(max) of 0.184 (0.069) ng/mL was reached at 13.76 (3.56) minutes after administration of intranasal fentanyl. The mean measured C(max) was 0.22 (0.088) ng/mL. CONCLUSIONS: In these women who had undergone breast reduction or augmentation surgery, a single preprocedural dose of intranasal fentanyl was significantly more effective than placebo in reducing pain intensity over the hour after removal of surgical drains. However, there was no significant difference in pain intensity between fentanyl at the time of drain removal and placebo. Intranasal fentanyl was generally well tolerated. At the dose used (0.05 mg), plasma fentanyl concentrations were below the reported therapeutic window.

Morphine inhalation by cancer patients: a comparison of different nebulization techniques using pharmacokinetic, spirometric, and gasometric parameters.

Despite numerous case reports suggesting the value of morphine (M) nebulization in the treatment of breathlessness, only a few clinical trials have been able to support this. The reason for this could lie in the lack of understanding of the localization of opioid receptors in the airways and the biopharmaceutics and pharmacokinetics of nebulized morphine. In the present study, we compared two different methods of pneumodosimetric nebulization: the Bronchial Control Treatment System-Sidestream (BCTS-S) and the Bronchial Control Treatment System-Micro Cirrus (BCTS-MC). The first method delivers relatively large aerosol particles (2-5microm) preferentially to the bronchial tree and trachea. In the BCTS-MC method, small aerosol particles (0.5-2microm) mostly reach the alveoli. Ten patients with cancer were randomly assigned to either the BCTS-S or BCTS-MC inhalation of 5 mg morphine HCl. Patients using the BCTS-S method inhaled a morphine dose in 6.6+/-2 minutes, whereas with the BCTS-MC method, the inhalation time was 28.8+/-8 minutes. The areas under the curve of morphine and glucuronides were several times higher after BCTS-S than after BCTS-MC. The proportion of morphine-3-glucuronide to morphine-6-glucuronide (M6) was, on average, close to one for both methods. From the same amount of morphine in the BCTS-S method, five times more M6 was produced. In both methods, the time to maximum concentration for morphine metabolites was 20-40 minutes, much shorter than expected from oral, intranasal, or intravenous administration. The study shows that the method of inhalation may have a profound effect on the pharmacokinetics of morphine. It is possible that the lungs metabolize morphine to glucuronides themselves and in different proportions from those seen after systemic administration. The BCTS-S method was found to be potentially superior to the BCTS-MC method in local action in the lungs.

Population pharmacokinetics of oxaliplatin (85 mg/m2) in combination with 5-fluorouracil in patients with advanced colorectal cancer.

Pharmacokinetic (PK) studies of oxaliplatin, using a dose regimen of 85 mg/m, are lacking. A PK model may be used in future studies to investigate the relationship between pharmacokinetics and dose limiting toxicity. The purpose of this study was to construct a population PK model to describe platinum (Pt) concentrations in plasma in 33 patients with colorectal cancer. The secondary objective was to determine the relationship between the amount of Pt in 24-hour urine and the amount of Pt in fractionated urine collection periods. Plasma and urine samples were collected from patients during their first oxaliplatin treatment course. Population PK analysis was performed with WinNonMix. The model that best described the Pt concentrations in plasma was a two-compartment PK model. The elimination clearance (CL) and the elimination clearance of the peripheral compartment (CL2) (median +/- SE) were 25.2 +/- 6.3 L/hr and 68 +/- 24.8 L/hr, respectively. The median volume of distribution (V1) was determined to be 41.6 +/- 9.4 L and the median volume of distribution of the peripheral compartment (V2) was 452.5 +/- 96.4 L. The relationship between the cumulative amount of Pt in urine in the first 12 hours compared with the amount of Pt in 24 hours urine was reflected by a correlation coefficient (r2) of 0.95. The cumulative Pt concentration in urine in the first 10 hours and the first 8 hours compared with 24 hours was reflected by correlation coefficients r2 = 0.93 and r2 = 0.897, respectively. This PK model could be useful in identifying predictors for PK and pharmacodynamic variability to individualize dosing. The results of this study suggest that fractionated urine samples can replace 24-hour urine collection.