Outlook: Clinical Trials

Michele Reed, PharmD
Published Online: Monday, March 14, 2011
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Rifaximin in IBS Without Constipation
Recent data from 2 phase 3, doubleblind, placebo-controlled trials (TARGET 1 and TARGET 2) show that a 2-week period of rifaximin treatment relieved symptoms associated with irritable bowel syndrome (IBS), including bloating, abdominal pain, and loose or watery stools.1 The trials randomized patients who had IBS without constipation to receive either rifaximin 550 mg or placebo 3 times daily for a 2-week treatment period. Study subjects were then followed for an additional 10 weeks. The primary end point of the study was the proportion of patients who had adequate relief, defined as self-reported relief of symptoms for at least 2 of the first 4 weeks after treatment, of global IBS symptoms. The key secondary end point was the proportion of patients who had adequate relief of bloating associated with IBS.

Combined results from both trials showed that rifaximin was significantly more effective at relieving global IBS symptoms during the first 4 weeks after treatment, with 40.7% of patients in the rifaximin group reporting adequate relief compared with 31.7% of patients in the placebo group (P <0.001). Additionally, rifaximin showed superior efficacy in the secondary end point of bloating relief (40.2% vs 30.3% in the rifaximin and placebo groups, respectively; P <0.001). Investigators concluded that rifaximin treatment for 2 weeks provided significant relief from IBS symptoms in patients who had IBS without constipation.

Phase 2 Study of West Nile Virus Vaccine
In a recent phase 2 trial in healthy adults, the immunogenicity, viremia, and safety of the ChimeriVax-WN02 vaccine was assessed.2 In part 1 of the study, subjects aged 18 to 40 years were randomized to 1 of 4 treatment groups: ChimeriVax- WN02 3.7- × -105 plaque-forming units (PFU), 3.7 × 104 PFU, 3.7 × 103 PFU, or placebo. In part 2, subjects aged 41 to 64 years and 65 years and older were randomized to receive ChimeriVax-WN02 3.7 × 105 PFU or placebo.

Seroconversion was achieved at day 28 by more than 96% of subjects in the active treatment groups of both parts of the study. In the first part of the study, neutralizing antibody titers were higher at day 28 and viremia levels were lower with the highest dose. The adverse event profile was similar between the dose groups in this part of the study. In part 2, antibody titers and viremia levels were higher in subjects 65 years and older, and more subjects between the ages of 41 and 64 years experienced adverse events. Investigators concluded that the ChimeriVax-WN02 vaccine was highly immunogenic in younger adults and the elderly, and it was well tolerated at all dose levels and in all age groups investigated.

Tadalafil Once Daily for Erectile Dysfunction
In a recent randomized, double-blind, placebo-controlled, parallel-group study, the onset of efficacy of tadalafil was evaluated.3 Investigators randomized 372 men to receive tadalafil 2.5 or 5 mg or placebo once daily for 14 days. Randomization was preceded by a 4-week run-in period and followed by a 14-day open label extension period of tadalafil 5 mg once daily. The primary end point of the study was the cumulative percentage of men with a successful intercourse attempt during the first 4 days of therapy. The secondary end point was percentage of successful attempts during the study.

Results showed that, compared with placebo, significantly more men in the tadalafil 5 mg group achieved successful intercourse (48.6% vs 36.6%; P <0.025). The tadalafil 2.5 mg dose did not differ significantly from placebo in the primary end point; however, it showed a significantly higher percentage of successful intercourse attempts by day 3 compared with placebo (35.5% vs 27.2%; P <0.025). Investigators concluded that tadalafil, dosed at 2.5 and 5 mg, is effective within a few days of therapy initiation.

Low Dose Oral Desmopressin for Nocturnal Polyuria in BPH
In a recent randomized, placebo-controlled clinical study, the long-term efficacy and safety of low dose oral desmopressin for nocturnal polyuria in elderly patients with benign prostatic hyperplasia (BPH) was evaluated.4 A total of 115 patients were randomized to receive desmopressin 0.1 mg (n = 57) or placebo (n = 58) orally at bedtime.

Results showed that oral desmopressin significantly decreased nocturnal urine and the number of nocturia episodes (P <0.01). Additionally, desmopressin significantly prolonged the first sleep period (P <0.01). The study concluded that desmopressin is an effective and well-tolerated treatment for nocturnal polyuria in patients with BPH. Desmopressin induced statistically, but not clinically significant, hyponatremia after 12 months of treatment. Investigators recommended assessment of serum sodium at least at 1 week post-treatment in cases of long-term desmopressin administration. PT


Dr. Reed received her doctor of pharmacy degree from the University of the Sciences in Philadelphia, Pennsylvania, and currently works as a medical editor in the greater Philadelphia area.



References
1. Pimentel M, Lembo A, Chey WD, et al. Rifaximin therapy for patients with irritable bowel syndrome without constipation. N Engl J Med. 2011;364(1):22-32.

2. Biedenbender R, Bevilacqua J, Gregg AM, Watson M, Dayan G. Phase II, randomized, double-blind, placebo-controlled, multicenter study to investigate the immunogenicity and safety of a West Nile virus vaccine in healthy adults. J Infect Dis. 2011;203(1):75-84.

3. Seftel A, Goldfischer E, Kim ED, Dula E, Zeigler H, Burns P. Onset of efficacy of tadalafil once daily in men with erectile dysfunction: a randomized, double-blind, placebo controlled trial. J Urol. 2011;185(1):243-248.

4. Wang CJ, Lin YN, Huang SW, Chang CH. Low dose oral desmopressin for nocturnal polyuria in patients with benign prostatic hyperplasia: a double-blind, placebo controlled,
randomized study. J Urol. 2011;185(1):219-223.



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