What kind of Tachycardia do you have? Tachycardia is any heart rate over 100. If it's just sinus Tachycardia, I probably wouldn't worry much.
What medication are you referring to that you don't want to take?
Are you talking about a beta blocker? I mean if your heart rate is always high you may need it and they treat high blood pressure. The benefits usually out weight the risks.
The others have said it. However it can not be overstated..
If you have concerns about your meds you need to make it a priority to contact your physician ASAP and tell him precisely your concerns to include your lack of desire to take the medication.
This type of unfiltered honesty is necessary in order for the physician to better explain the pros and cons of the management strategy.
One one hand, if your condition is bad enough to be a life-or-death type of problem; give them a chance to convince you.
However if your condition is NOT that type of problem; then calling your doctor and expressing your concerns is an opportunity to explore alternate treatment strategies until you find one you’re comfortable with!