Knowledge of myometrial regulation is essential to understanding preterm labour. Cholesterol depleting agents have been reported to perturb the myometrial membrane microenvironment and therefore key ion channels (1), studies have also demonstrated the pleiotropic effects of such agents (2). Our hypothesis is that simvastatin decreases myometrial contractions via K+channel blockade and inhibition of its pleiotropic effects, including nitric oxide production and isoprenylated proteins. We aim to investigate effects of simvastatin on human myometrium. Myometrial biopsies were collected with informed written consent from patients undergoing elective caesarean section (>37 weeks). Tissue was mounted for isometric tension recordings and effects of simvastatin (33 nM – 330 μM) on spontaneous contractility, in the absence and presence of SK channel blocker apamin (500 nM), BK channel blocker paxilline (1 μM), broad-acting K+ channel blocker TEA (5 mM), NOS inhibitor L-NAME (1.2 mM) and isoprenoid GGPP (30 μM) assessed. Cholesterol and protein were measured in untreated and treated myocytes, using Amplex red and bicinchoninic acid assays respectively. In all assay-based experiments, 15 mM methyl-β-cyclodextrin (MCD) was used as a comparative cholesterol-depleting agent. Data are presented as means + SEM and compared using ANOVA. Simvastatin significantly decreased contractions until cessation at 330 μM (p <0.0001, n=6) in contrast to MCD treatment which increased contractions (p <0.0001, n=6). Selective inhibition of both SK (p<0.05, n=6), (IC50 = 2.56e-6 vs. 2.10e-7 M), BK (p<0.01, n=6), (IC50=4.41e-6 vs. 2.10e-7 M) and addition of both inhibitors (p<0.001, n=5), (IC50 = 1.68e-5 vs. 2.10e-7 M) produced a rightward shift of the concentration-response curve. Broad Inhibition of K+ channels with TEA elicited significant partial inhibition of simvastatin relaxation (p<0.0001, n=5), (IC50 = 1.84e-4 vs. 2.10e-7 M). Replenishment with GGPP had no effect on simvastatin -induced relaxation (p>0.05, n=6), however NOS inhibition was able to significantly inhibit simvastatin relaxation (p<0.05, n=4). Finally, only MCD treatment significantly decreased cholesterol concentration (p<0.001, n=5) while the total protein concentration was unchanged. Data demonstrated evidence of K+ channel modulation by simvastatin. Absence of cellular cholesterol modulation and significant inhibition of simvastatin-induced relaxation by L-NAME, suggests an alternative mechanism of statin action, independent of HMG-CoA inhibition of novel cholesterol synthesis. Myometrial relaxation via simvastatin suggests that statins may have implications as tocolytic agents in the treatment of preterm labour, warranting further investigation into their mechanisms and therapeutic potential.