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“There were lots of reasons to think that it would work," Boston University rese"...
Mechanism Of Action
Alprostadil induces erection by relaxation of trabecular smooth muscle and by dilation of cavernosal arteries. This leads to expansion of lacunar spaces and entrapment of blood by compressing the venules against the tunica albuginea, a process referred to as the corporal veno-occlusive mechanism.
There are no results from pharmacodynamic studies in humans.
Following intracavernosal injection of 20 mcg alprostadil, mean peripheral plasma concentrations of alprostadil at 30 and 60 minutes after injection (89 and 102 picograms/mL, respectively) were not significantly greater than baseline levels of endogenous alprostadil (96 picograms/mL). Plasma levels of alprostadil were measured using a radioimmunoassay method. Alprostadil is bound in plasma primarily to albumin (81% bound) and to a lesser extent αglobulin IV-4 fraction (55% bound). No significant binding to erythrocytes or white blood cells was observed.
Alprostadil is converted to compounds, which are further metabolized prior to excretion. Following intravenous administration, approximately 80% of circulating alprostadil is metabolized in one pass through the lungs, primarily by beta-and omega-oxidation. Following intracavernosal injection of 20 mcg alprostadil, peripheral levels of the major circulating metabolite, 13, 14-dihydro-15-oxo-PGE1, increased to reach a peak 30 minutes after injection and returned to pre-dose levels by 60 minutes after injection.
The metabolites of alprostadil are excreted primarily by the kidney, with almost 90% of an administered intravenous dose excreted in urine within 24 hours post-dose. The remainder of the dose is excreted in the feces. There is no evidence of tissue retention of alprostadil or its metabolites following intravenous administration.
Pharmacokinetics In Specific Populations
The potential effect of age on the pharmacokinetics of alprostadil has not been formally evaluated.
The potential effect of race in the pharmacokinetics of alprostadil has not been formally evaluated.
Renal And Hepatic Insufficiency
The pharmacokinetics of alprostadil have not been formally studied in patients with renal or hepatic insufficiency.
The efficacy of CAVERJECT Sterile Powder was investigated in men with a diagnosis of erectile dysfunction due to psychogenic, vasculogenic, neurogenic, and/or mixed etiology in two double-blind placebo controlled studies (Study 1 and Study 2) and in one 6-month open-label study (Study 3). In clinical studies (Study 1 and Study 3), over 80% of patients experienced an erection sufficient for sexual intercourse after intracavernosal injection of CAVERJECT Sterile Powder.
Study 1: A total of 153 men with ED with a mean age of 53 years (range 23–69 years) were enrolled. The study had three phases: a 2.5 week, randomized, double-blind, placebo-controlled crossover phase in which each man received in-office injections of placebo or 2.5 mcg, 5 mcg, 7.5 mcg, or 10 mcg of CAVERJECT Sterile Powder; a 2 week, open-label, in-office dose-titration phase to identify the optimum home-use dose (the latter dose was defined as a dose inducing an erection sufficient for intercourse and lasting ≤ 60 minutes); and a 4-week open-label, at-home phase. In the double-blind placebo-controlled, crossover phase, each dose of CAVERJECT was significantly more effective than placebo by clinical evaluation (“full penile rigidity”) and by RigiScan criteria ( ≥ 70% rigidity for at least 10 minutes); there was no response to placebo. The percentage of responders increased with increasing doses of CAVERJECT. The overall response rates in the crossover and dose-titration phases were 76% (117/153) by clinical evaluation and 51% (78/152) by RigiScan criteria. Seventy-three percent of the injections in 102 men who used CAVERJECT in the at-home phase resulted in satisfactory intercourse. Seventy-five percent of the men who used CAVERJECT in the at-home phase remained on the dose identified as optimum for them during the dose-titration phase; 17% and 8% of the men decreased or increased their dose, respectively. The mean duration of erection per injection was 70.8 minutes.
Study 2: A total of 296 men with ED with a mean age of 54 years (range 21–74 years) were enrolled in this double-blind, placebo controlled, parallel-arm design study. The men were randomly assigned to one of five groups and received either a single dose of placebo, 2.5 mcg, 5 mcg, 10 mcg, or 20 mcg of CAVERJECT Sterile Powder. No patient responded to placebo. The differences in the response rates in both the clinical and the RigiScan evaluations between each of the doses of CAVERJECT and placebo were statistically significant. There was also a statistically significant dose-response relationship with higher clinical response rates and higher RigiScan response rates with increasing doses of CAVERJECT (with exception of the 10-mcg dose). The mean duration of erection after injection ranged from 12 minutes after the 2.5mcg dose to 44 minutes after the 20-mcg dose and the relationship was linear (p = .025, linear regression analysis).
Study 3: The efficacy of CAVERJECT Sterile Powder was further evaluated in a 6-month, open-label, at-home study in 683 men with ED with a mean age of 58 years (range 20–79 years). The optimum dose of CAVERJECT was established by titration in 89% of men (606/683). A total of 471/683 men (69%) completed the 6-month study. Eighty-seven percent of the 13,762 injections of CAVERJECT administered resulted in satisfactory sexual activity. The mean duration of erection was 67.5 minutes.
The formulation of alprostadil contained in CAVERJECT IMPULSE was compared to CAVERJECT Sterile Powder in 87 men with ED in a single-blind, crossover study. The doses used by the patients in the study ranged from 2.5 mcg to 20 mcg and were the same for both formulations. The efficacy of the two formulations was shown to be comparable, as assessed by the 30-point erectile function (EF) domain score from the International Index of Erectile Function (IIEF) and by a physician-assessment score for erectile response. The mean EF domain scores for CAVERJECT Sterile Powder and the formulation contained in CAVERJECT IMPULSE were 26.6 (SD=5.3) and 27.6 (SD=3.8), respectively. The mean physician's assessment scores for CAVERJECT Sterile Powder and the formulation contained in CAVERJECT IMPULSE were 2.6 (SD=0.6) and 2.7 (SD=0.5), respectively, based on a scale of 0 (no tumescence) to 3 (full rigidity).
Last reviewed on RxList: 5/16/2016
This monograph has been modified to include the generic and brand name in many instances.
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