Fenoverine: a novel synchronizer of smooth muscle motility by interference with cellular calcium flow

The incidence, risk factors, and clinical outcomes of rhabdomyolysis associated with fenoverine prescription: a retrospective study in South Korea (1999–2014)

Background

Fenoverine is a spasmolytic drug that has been used to treat abdominal pain. Although sporadic case reports or case series of rhabdomyolysis associated with fenoverine have been published, there are no studies evaluating the incidence, risk factors, and clinical outcomes of rhabdomyolysis associated with fenoverine prescription.

Methods

We retrospectively reviewed the medical records of 22 patients admitted with rhabdomyolysis associated with fenoverine from January 1999 to December 2014, while excluding other well-known risk factors of rhabdomyolysis. This period was subdivided into two periods, January 1999–December 2007 and January 2008–December 2014. We analyzed the clinical and laboratory characteristics, and the prognosis of fenoverine associated with rhabdomyolysis for these times.

Results

The incidence of rhabdomyolysis associated with fenoverine was 0.27% during the total period (22/8257), 0.34% in the first period (18/5298), and 0.14% in the second period (4/2959) (p < 0.001). Rhabdomyolysis occurred in 19 liver cirrhosis (LC) patients (2.03%), whereas only 3 cases (0.04%) occurred in non-LC patients (p < 0.001). Drug duration, total dose, muscle enzymes, and clinical characteristics were not different between the LC and non-LC groups. Acute renal failure (ARF) occurred in 5 patients in the LC group and 2 patients in the non-LC group (p = 0.227). Severity of hepatic derangement according to the Child-Pugh classification was not different between the ARF group and non-ARF group (p = 0.227). Four patients died, having complications of oliguric ARF (p = 0.005) and underlying severe LC (p = 0.017). Higher serum lactate dehydrogenase, blood urea nitrogen, creatinine, and potassium levels but lower serum sodium levels were found in the group that died (p = 0.001).

Conclusions

Physicians should carefully prescribe fenoverine because it may cause rhabdomyolysis, especially in patients with LC.

Determination of fenoverine, a modulator of smooth muscle motility, in capsules and in human plasma: application to dosage form stability and a pilot study in humans

Fenoverine is a novel, potent, musculotropic, spasmolytic agent that affects primarily the gastrointestinal tract, bile duct, and female genital organs. A simple, specific, and accurate HPLC method was developed for the determination of fenoverine in capsules and plasma. This method has been successfully applied to stability studies of fenoverine capsules and to a pilot study in a normal, healthy volunteer following oral administration of fenoverine. For the determination of fenoverine in capsules, a Nucleosil 5-micron CN column, with acetonitrile:0.1 M ammonium acetate (60:40) as mobile phase and detection at 254 nm, was employed. The mean correlation coefficient of the calibration curve (n = 6) for the assay was 0.9999 over a concentration range of 24.6 to 147.6 micrograms/mL of fenoverine standard solutions. Fenoverine did not decompose significantly at 4, 45, 55, and 65 degrees C for 3 months. The mean correlation coefficients of within-day and between-day calibration curves were 0.9995 and 0.9999, respectively, over a range of 10 to 1000 ng/mL of fenoverine in plasma. The limit of detection was 10 ng in plasma.

Fenoverine inhibition of calcium channel currents in single smooth muscle cells from rat portal vein and myometrium

1. The effects of fenoverine, an antispasmodic drug, have been studied on the Ca2+ channel currents of isolated cells from rat portal vein and pregnant myometrium by the patch-clamp technique (whole-cell configuration). 2. Fenoverine inhibited both fast and slow Ca2+ channel currents in a concentration-dependent manner. Half-inhibition of fast Ca2+ channel current (holding potential of -70 mV) and slow Ca2+ channel current (holding potential of -40 mV) in portal vein smooth muscle were obtained at concentrations of 7.5 and 1.9 microM, respectively. In myometrium, the fenoverine concentration which blocked 50% of the slow Ca2+ channel current (holding potential of -70 mV) was 2.3 microM. 3. Administration of fenoverine at rest reduced both Ca2+ channel currents. Currents activated repetitively, at a rate between 0.05 and 0.1 Hz, were inhibited equally which indicates an absence of use-dependent inhibition. 4. When cells held at depolarized membrane potentials at which fast or slow Ca2+ channel currents were strongly inactivated, the inhibitory effects of fenoverine were enhanced on both Ca2+ channel currents which indicates that the fenoverine-induced inhibition was voltage-dependent. The fenoverine concentrations which blocked the inactivated Ca2+ channels were 5-7 times lower than those which blocked the resting Ca2+ channels. 5. Our results show that fenoverine depresses inward currents through fast and slow Ca2+ channels. This effect may be explained by the preferential binding of fenoverine to resting Ca2+ channels. In addition, fenoverine has a higher affinity for inactivated Ca2+ channels than for resting channels.