The Effect of Single and Multiple Doses of Rifampin on the Pharmacokinetics of Doravirine in Healthy Subjects

BACKGROUND AND OBJECTIVE

Doravirine is a novel, next-generation, non-nucleoside reverse transcriptase inhibitor in development for the treatment of human immunodeficiency virus-1 infection in combination with other antiretrovirals. Doravirine is a substrate for cytochrome P450 (CYP) 3A and P-glycoprotein. Rifampin (rifampicin) is used for treating tuberculosis in patients who are co-infected with human immunodeficiency virus. Rifampin demonstrates organic anion-transporting polypeptide 1B1 and P-glycoprotein inhibition after single-dose administration and CYP3A and P-glycoprotein induction after multiple-dose administration. The objective of this study was to evaluate the effects of co-administration of single and multiple doses of rifampin on doravirine pharmacokinetics.

METHODS

In period 1 of this open-label, two-period, fixed-sequence study in healthy adults, subjects received single-dose doravirine 100 mg; blood samples for measuring plasma concentration were collected pre-dose and up to 72 h post-dose. In period 2, following a 7-day washout, subjects received doravirine 100 mg and rifampin 600 mg on day 1, rifampin 600 mg daily on days 4-18, with doravirine 100 mg co-administered on day 17; blood samples were collected pre-dose and up to 72 h post-dose on day 1 and up to 48 h post-dose on day 17. Safety assessments included adverse events, physical examinations, vital signs, and clinical laboratory measurements.

RESULTS

Ten subjects completed the study. Doravirine area under the concentration-time curve from time zero extrapolated to infinity and plasma concentration at 24 h post-dose were comparable in the presence and absence of single-dose rifampin [geometric mean ratios (90% confidence intervals)] of 0.91 (0.78-1.06) and 0.90 (0.80-1.01), respectively. Doravirine maximum plasma concentration increased when co-administered with single-dose rifampin vs. doravirine alone, geometric mean ratio (90% confidence interval): 1.40 (1.21-1.63). Reductions in doravirine geometric mean ratios (90% confidence interval), area under the concentration-time curve from time zero extrapolated to infinity: 0.12 (0.10-0.15), plasma concentration at 24 h post-dose: 0.03 (0.02-0.04), maximum plasma concentration: 0.43 (0.35-0.52), and apparent terminal half-life were observed when co-administered with multiple-dose rifampin vs. doravirine administered alone. Doravirine was well tolerated. Adverse events were mild and resolved by study completion.

CONCLUSIONS

Doravirine co-administration with single-dose rifampin indicated that inhibition of organic anion-transporting polypeptide uptake transporters and P-glycoprotein has little impact on doravirine pharmacokinetics. Long-term co-administration of rifampin or other strong CYP3A inducers with doravirine will likely reduce its efficacy.

Diagnostic pelvic computed tomography in the rectal-injured combat casualty

BACKGROUND

The current standard for evaluating trauma patients for penetrating rectal injury is to perform a rigid proctoscopy. This can be laborious and inaccurate. Injuries are often not visualized and a small number of unnecessary colostomies may be created. Computed tomography (CT) scanning of the pelvis may be useful in identifying penetrating rectal injuries.

STUDY DESIGN

A retrospective analysis was performed on data regarding all casualties admitted to the 10th Combat Support Hospital during the period of November 2005 through March 2006. Nineteen patients were identified. Patients that were hemodynamically stable underwent preoperative CT scanning. All rectal injuries diagnosed preoperatively were confirmed through a different diagnostic modality in the OR.

RESULTS

Nineteen patients with rectal injury or suspected rectal injury were identified. Eight of the 19 were hemodynamically unstable in the emergency medical treatment area and were taken emergently to surgery. For discussion, only stable patients with gunshot wound or blast/fragmentation injury mechanisms were included. No injuries were missed by CT scanning, but there were two false-positive scans.

CONCLUSIONS

In our brief experience, CT scanning was a useful screening tool to assist in identifying patients with penetrating traumatic rectal injuries. It allowed us to improve triage and make effective use of limited operative resources.

The clinical anatomy of the cephalic vein in the deltopectoral triangle

Identification and recognition of the cephalic vein in the deltopectoral triangle is of critical importance when considering emergency catheterization procedures. The aim of our study was to conduct a cadaveric study to access data regarding the topography and the distribution patterns of the cephalic vein as it relates to the deltopectoral triangle. One hundred formalin fixed cadavers were examined. The cephalic vein was found in 95% (190 right and left) specimens, while in the remaining 5% (10) the cephalic vein was absent. In 80% (152) of cases the cephalic vein was found emerging superficially in the lateral portion of the deltopectoral triangle. In 30% (52) of these 152 cases the cephalic vein received one tributary within the deltopectoral triangle, while in 70% (100) of the specimens it received two. In the remaining 20% (38) of cases the cephalic vein was located deep to the deltopectoral fascia and fat and did not emerge through the deltopectoral triangle but was identified medially to the coracobrachialis and inferior to the medial border of the deltoid. In addition, in 4 (0.2%) of the specimens the cephalic vein, after crossing the deltopectoral triangle, ascended anterior and superior to the clavicle to drain into the subclavian vein. In these specimens a collateral branch was observed to communicate between the cephalic and external jugular veins. In 65.2% (124) of the cases the cephalic vein traveled with the deltoid branch of the thoracoacromial trunk. The length of the cephalic vein within the deltopectoral triangle ranged from 3.5 cm to 8.2 cm with a mean of 4.8+/-0.7 cm. The morphometric analysis revealed a mean cephalic vein diameter of 0.8+/-0.1 cm with a range of 0.1 cm to 1.2 cm. The cephalic vein is relatively large and constant, usually allowing for easy cannulation.

Dexamethasone does not significantly contribute to the response rate of docetaxel and estramustine in androgen independent prostate cancer

PURPOSE

We evaluated the independent response rate of dexamethasone before docetaxel and estramustine administration as measured by changes in serum prostate specific antigen (PSA) in patients with androgen independent prostate cancer.

MATERIALS AND METHODS

A total of 12 patients received 20 mg. dexamethasone orally every 6 hours for 3 doses repeated every 3 weeks before starting cytotoxic therapy with estramustine and docetaxel. After progression on dexamethasone 280 mg. estramustine orally 3 times daily on days 1 to 5 and 70 mg./m.2 docetaxel intravenously for 1 hour on day 2 were given.

RESULTS

None of the patients initially treated with dexamethasone monotherapy (median 1 cycle, range 1 to 5) had a PSA decline of 50% or greater. Median PSA increase on monotherapy was 47% (range 0% to 22%). On estramustine and docetaxel therapy PSA decreased 50% or greater in 11 patients (92%, 95% confidence intervals [CI] 60 to 99) and 80% or greater in 7 (58%, 95% CI 29 to 84), and normalized in 5 (42%, 95% CI 16 to 71), with a median duration of response of 153 (range 42 to 371), 132 (range 84 to 287) and 84 (range 21 to 174) days, respectively. Median times to reach 50% and 80% decreases in baseline PSA were 21 (range 21 to 209) and 63 (range 21 to 138) days, respectively. In 9 patients (75%, 95% CI 43 to 93) PSA decreased at least 50% by week 9. Of 4 patients with bidimensionally measurable disease 3 had a partial response. Median time to progression was 263 days (range 91 to 378).

CONCLUSIONS

Administration of 20. mg. dexamethasone orally every 6 hours for 3 doses every 3 weeks does not significantly contribute to the PSA response rate of estramustine and docetaxel.

Phase I/II studies of docetaxel (Taxotere) combined with estramustine in men with hormone-refractory prostate cancer

Evaluation of the combined regimen of estramustine and docetaxel (Taxotere; Rhône-Poulenc Rorer, Collegeville, PA) in men with hormone-refractory prostate cancer is in its early stages. While this combination is promising in terms of efficacy, adverse events associated with estramustine are a concern. Estramustine has been associated with side effects such as nausea, vomiting, edema, and serious vascular events. Reported here are the results of phase I and phase II trials in which 280 mg estramustine was given three times daily on days I to 5 in 21-day treatment cycles with docetaxel at varying doses. Data from patients evaluable thus far support the efficacy of this combination, both in chemotherapeutically naive patients and in those who have had prior therapy. A survival benefit from this combination appears achievable from these early studies. As significant antitumor activity can be achieved with docetaxel alone, future studies need to define the minimal dose of estramustine for this combination.

Phase I trial of docetaxel with estramustine in androgen-independent prostate cancer

PURPOSE

To evaluate the toxicity, efficacy, and pharmacokinetics of docetaxel when combined with oral estramustine and dexamethasone in a phase I study in patients with progressive metastatic androgen-independent prostate cancer.

PATIENTS AND METHODS

Thirty-four men were stratified into minimally pretreated (MPT) and extensively pretreated (EPT) groups. Estramustine 280 mg PO tid was administered 1 hour before or 2 hours after meals on days 1 through 5, with escalated doses of docetaxel from 40 to 80 mg/m2 on day 2. Treatment was repeated every 21 days.

RESULTS

Thirty-four patients were assessable for toxicity and 33 for response. In the MPT patients, dose-limiting myelosuppression was reached at 80 mg/m2, with six patients experiencing grade 3/4 granulocytopenia. In EPT patients, escalation above 70 mg/m2 was not attempted. Fourteen MPT (70%) and six EPT (50%) patients had a > or = 50% decline in serum PSA on two consecutive measurements taken at least 2 weeks apart. The overall 50% PSA response rate was 63% (95% confidence interval [CI], 28% to 81%). Of the 18 patients with bidimensionally measurable disease, five (28%; 95% CI, 11% to 54%) achieved a partial response. At the time of entry onto the study, 15 patients required narcotic analgesics for bone pain; after treatment, eight (53%) discontinued their pain medications. The area under the curve for docetaxel increased linearly from 40 to 70 mg/m2. At 80 mg/m2, the measured area under the curve was 8.37 (standard deviation, 0.724), which was significantly higher than the previously reported values.

CONCLUSION

The recommended phase II dose of docetaxel combined with estramustine is 70 mg/m2 in MPT patients and 60 mg/m2 in EPT patients. This combination is active in men with androgen-independent prostate cancer.

Device choice and experience level in endoscopic foreign object retrieval: an in vivo study

BACKGROUND

Successful foreign object retrieval may depend on device choice and the experience level of the endoscopist, although these factors have not been systematically evaluated.

METHODS

In anesthetized pigs, the ability to retrieve foreign objects (metal tack, button disc battery, wooden toothpick) placed endoscopically into the stomach was assessed. Seven university medical center gastroenterology attending physicians (5 clinical and 2 basic science research [BSR]), and 4 fellows-in-training participated. The devices used were the Roth retrieval net, rat tooth forceps, Dormia basket, polypectomy snare, and radial jaw forceps. The time to retrieve each object into an esophageal overtube within a 5 minute maximum was measured.

RESULTS

Only the Roth net and Dormia basket were successful in retrieving the button disc battery, although the Roth net was superior (100% vs 27%, Fisher p < 0.025). All devices were equally successful at retrieving the tack (82% to 100%, p = NS). The snare was significantly faster than the Roth net (p < 0.05). For the tack, there was significantly fewer difficulties encountered with the snare than the Roth net (Fisher p < 0.03). The Roth net was incapable of retrieving the toothpick; the other devices were equally successful (91% to 100%). The clinical attendings had a significantly higher success rate (95%) than the fellows (82%, chi squared p < 0.05) or combined fellows/BSR attendings (80%, p < 0.02), and were significantly faster than the fellows (p < 0.0002) or the fellows/BSR attendings (p < 0.0003).

CONCLUSIONS

The Roth net is the best device for retrieving smooth objects such as the button disc battery. For sharp objects, such as the tack and toothpick, best results were achieved with the snare, although the forceps were also effective. More experienced endoscopists had higher success rates and faster retrieval times. Both device choice and the experience level of the endoscopists have an impact on successful foreign object retrieval.

A late defect in wound healing associated with recurrent spontaneous pneumothoraces: a presumptive role for abnormal collagenase activity

This case report concerns an individual with a defect in wound healing which resulted in recurring, bilateral pneumothoraces during the late postoperative period. This patient had no history of systemic disease or wound healing abnormalities before his recurrent wound disruption. Physical examination and routine biochemical studies failed to identify any causative agent for the multiple wound dehiscences in the patient. Histologic examination of scar tissue showed collagen fiber bundles with a diameter 50% less than that of normal fibrils. Elastic fibers were barely visible, and the scar tissue included a large number of inflammatory cells. A significant finding was an elevated and aberrant expression of collagenase by a fibroblast cell line established from a skin biopsy specimen. This enhanced level of collagenase expression could be inhibited by treatment of the cells with diphenylhydantoin, an inhibitor of collagenase biosynthesis. After initiation of diphenylhydantoin therapy, the patient's scar formation normalized with the recurrent pneumothoraces. These findings support the conclusion that an abnormal expression of collagenase resulted in enhanced degradation of collagen in the patient's wounds, thereby leading to wound dehiscence.