You would expect a person to be hypertensive and tachycardic following exposure to all, EXCEPT?

In the context of substances that typically lead to hypertension (high blood pressure) and tachycardia (increased heart rate), most psychoactive drugs, pseudoephedrine, and bath salts are known to stimulate the central nervous system, which can result in increased cardiovascular activity.

Psychoactive drugs, such as stimulants, often cause heightened alertness and energy levels, which can elevate blood pressure and heart rate. Pseudoephedrine, commonly used as a decongestant, can have sympathomimetic effects, leading to similar cardiovascular responses. Bath salts, a synthetic stimulant, are notorious for causing significant increases in heart rate and blood pressure due to their powerful effects on the nervous system.

In contrast, phenobarbital is a barbiturate that functions as a central nervous system depressant. Its primary use is for sedation and to control seizures. Instead of stimulating the cardiovascular system, phenobarbital is more likely to lead to a decrease in heart rate and blood pressure because of its calming effects on the nervous system. Thus, it stands out among the choices as the substance one would not expect to cause hypertension and tachycardia following exposure.