Are atropine and epinephrine’s effect on the heart able to be compared proportionally? I know atropine can help bradycardia, and smaller amounts of epinephrine can as well.
gettingvetted here.
They are two different classes of drug. Atropine is an anticholinergic, which means that it blocks transmission of parasympathetic ("rest and digest") signals. Since parasympathetic influence causes slowed heart rate, low blood pressure, etc, removal of these influences (for example, when under anesthesia) causes a sympathetic effect ("fight or flight"), raising the heart rate and the blood pressure by generally blocking all of the opposite signals. In itself, atropine does not cause stimulation of any particular nerve - just blocks the effects of other hormones and drugs.
Meanwhile, epinephrine is an adrenergic agonist, meaning that it specifically activates sympathetic signals. Epinephrine causes elevated blood pressure by constricting blood vessels far away from the heart, while decreasing the pressure in the vessels around the heart itself. However, its main effect is to cause that elevated blood pressure by stimulating the heart to contract harder and somewhat faster. Its main effect is on blood pressure, rather than heart rate, although it does have some function there as well.
So, sure, they are comparable - atropine elevates both heart rate and blood pressure by blocking signals for low heart rate/pressure. Meanwhile, epinephrine elevates mostly blood pressure by activating signals for high blood pressure. This is why they are often used together (among other drugs) when performing CPR.
