Final answer:
An adrenergic agonist is most likely to have caused the symptoms of tachycardia, mydriasis, normal blood pressure, and reduced sweating, as it stimulates the sympathetic nervous system.
Step-by-step explanation:
The symptoms of tachycardia, mydriasis, normal blood pressure, and reduced sweating after an IV drug injection suggest the involvement of the autonomic nervous system. Comparing the options given, these symptoms align most closely with the effects of an adrenergic agonist. Adrenergic agonists stimulate the sympathetic nervous system, mimicking the effects of adrenaline (epinephrine) and norepinephrine. This would lead to an increased heart rate (tachycardia) and pupil dilation (mydriasis). The lack of effect on blood pressure and decrease in sweating are consistent with some adrenergic drugs that have selective actions on certain types of adrenergic receptors. Therefore, the drug most likely to have caused these symptoms is an adrenergic agonist.
Answer: 3) Adrenergic agonist