I can't speak to your specific situation, but from my experience the most obvious effect is gastric. All other somatic effects are very similar to other psychedelics, increased heart rate, BP, temp, sweating, but none that I think are remotely dangerous. But I don't know about the safety or interactions of any medicine you may be taking.
I may be confusing the mental perception aspect to the physical aspect in regards to heart rate increase but its less stimulating to me then MDMA and far less stimulating then other amphetamines like meth or adderall. This is probably only perception but its less stimulating to me then LSD
I'm 64 and my blood pressure is in the 140+/75+ range. As it happened I was sharing the experience with a 64 Y/O MD and we talked a bit ebout what it might do. He felt like my overall health was fine and we had a fine time with no physical issuses at all except for a slight case of the "grins" whch I sometimes experience with stimulants.
You should go in 12" increments. This stuff is just to nasty tasting to tease it. A good potent dose from the cacti I have had was in the 24"-30" range. 12" should give you a good idea about the particular cacti's potentcy, yet not take the top of your head off. I don't feel that 4" worth of cactus would provide enough alkaloids to give you any idea of how it is going to effect you. Also make a tea or do one the extraction methods discussed in the forum.
I've never smoked herb on it. 12" is by no means a heavy trip. Once you taste how nasty the stuff is along with the time it takes to prepare it anything less to me would almost be not worthwhile. 12" to me is mostly a physical trip. I personally feel you need to put a little more faith in the medicine or maybe reconsider not doing it.
Guys I'm new to San Pedro but this Curandra ( Leslie) from Cuzco, Peru cooks it for a full 20 hours and I asked her if she had put honey in it(she didn't). It was a golden thick liquor that made for 10 sweet hours of being vitally present in my environment. And DJ, there are a fair amount of MD's out there that are pretty enlightened though they probably wouldn't say so in a regular office visit. Keep Lookin and do some online searching of San Pedro in Peru, especially Cuzco. Good luck and be good to yourself...if you have a sense of your own limits...Respect Those Limits.
If it's the diabetes meds, that stuff is nasty and has serious side effects. I'm doing much better without it.
I was referring to the San pedro. Some weed would probably go well with it, I may try it next time but it may add stress to whatever physical problems you're worried about. A headache at the end and some gi disturbance are the two negative physical effects I have experienced, may not be relevant to your experience but the effects could be increased due to your age.
DJ I've got her website address somewhere but I've only been back incountry for about 12 hours and still haven't found my ass let alone anything else...I'll get back to you on that. She may be a little guarded about her methods but I really have no idea. She was just an incrediably sweet, loving person who attended to us all as we melded with the jungle.