Mohta M, et al. - Researchers sought to define the effective dose of norepinephrine for management of post-spinal hypotension as well as compared its potency to phenylephrine. A predetermined dose of either phenylephrine or norepinephrine was administered to 100 consecutive patients who developed post-spinal hypotension. ‘Success’ was defined as correction of hypotension following one minute. They calculated ED95 and ED50 of phenylephrine and norepinephrine boluses as well as their potency ratio. For phenylephrine, ED95 and ED50 values were 43.1 µg and 33.2 µg, and these values were 3.7 µg and 3.2 µg for norepinephrine, using Probit analysis. The estimated relative potency ratio of norepinephrine and phenylephrine was 11.3. Compared to phenylephrine, norepinephrine was found to be approximately 11 times more potent. They concluded 100 μg phenylephrine should be almost equivalent to 9 μg norepinephrine when used as bolus doses for treatment of hypotension.