Equanil acts as a/an:

1. Artificial sweetener

2. Tranquilizer

3. Antihistamine

4. Antifertility drug

HINT: Equanil reduces stress.
Explanation:
STEP 1:
A tranquilizer refers to a drug which is designed for the treatment of anxiety, fear, tension, agitation, and disturbances of the mind, specifically to reduce states of anxiety and tension.

STEP 2:

The formula for Equanil is C9H18N2O4. It is a tranquilizer used to reduce stress.  It is used in controlling depression and hypertension.

Meprobamate | C9H18N2O4 - PubChem