Imidafenacin is an
antimuscarinic agent with high affinity for the M(3) and M(1)
muscarinic receptor subtypes and low affinity for the M(2) subtype, and is used to treat
overactive bladder. Several animal studies have demonstrated that
imidafenacin has organ selectivity for the bladder over the salivary glands, colon, heart, and brain. In Phase I studies in humans, the approximately 2.9-hour elimination half-life of
imidafenacin was shorter than that of other
antimuscarinics such as
tolterodine and
solifenacin.
Imidafenacin was approved for clinical use in
overactive bladder in Japan in 2007 after a randomized, double-blind, placebo-controlled Phase II study and a
propiverine-controlled Phase III study conducted in Japanese patients demonstrated that
imidafenacin 0.1 mg twice daily was clinically effective for treating
overactive bladder and was not inferior to
propiverine for reduction of episodes of incontinence, with a better safety profile than
propiverine. Several short-term clinical studies have demonstrated that
imidafenacin also improves
sleep disorders,
nocturia, and
nocturia-related quality of life. In addition, it is speculated that addon
therapy with
imidafenacin is beneficial for men with
benign prostatic hyperplasia whose
overactive bladder symptoms are not controlled by alpha-1
adrenoceptor antagonists. No
cognitive impairment or influence of
imidafenacin on the QTc interval has been observed. Although there have been very few relevant long-term clinical studies, the available information suggests the long-term efficacy, safety, and tolerability of
imidafenacin, with less frequent severe adverse events, such as dry mouth and
constipation. In addition,
imidafenacin can be used safely for a long time even for cognitively vulnerable elderly patients with symptoms of
overactive bladder. Thus, it is highly likely that
imidafenacin is safe, efficacious, and tolerable to control symptoms of
overactive bladder even over the long term. However, it remains unknown if the practical effectiveness of
imidafenacin is applicable to ethnic groups other than Japanese.