Help OTC meds or other accessible ways to lower heartrate?

[Scythe]

So my method's main lethal component is basically just massively lowering my heartrate and potentially triggering a cardiac arrest.

And I would like some additional meds/drugs to take with it to max my chances. I'm going to take some sleeping meds most likely to help sleep not to lower heart rate. Any suggestions from everyone here?

I also have ways to increase my red cell count and I'm wondering if I should do that.

I would also like OTC meds that increases heartrate, as my backup method is suppose to do the opposite. Massively increase heartrate and cause cardiac arrest. I'm taking alcohol with that, and I don't know what else.