I also recharged some of my old, wimped-out NTG ointment by puncturing a nifedipine capsule and mixing some of the liquid into it. It was as effective locally as NTG, and didn't produce so much of a headache. It's now two weeks after I started nifedipine. The fissure has healed and the spasms have been vastly reduced. By the way, premenopausal women may want to know that because nifedipine is a smooth-muscle relaxant, it also did wonders for my menstrual cramps.
Oral nifedipine helps end the spasm.
Finding other ways to manage the stress helps prevent the spasms from happening in the first place. Large doses of caffeine are definitely a problem. I'm reducing my caffeine consumption for the time being, from perhaps four cups of coffee a day to the equivalent of one. I've remained surprisingly free of caffeine-deprivation headaches. The usual caveats about moderation, of course, apply.