Can Sinarest make you sleepy? I feel very drowsy after taking it in the morning.

Yes, it is very normal to feel drowsy, sleepy, or tired after taking Sinarest. This is one of the most common and expected side effects of the medication. If drowsiness is severely affecting your daily life, you should talk to your healthcare provider.
Why You Feel Sleepy: The primary reason for the drowsiness is the presence of an ingredient called Chlorpheniramine Maleate, which is an older type of antihistamine. Antihistamines work by blocking the effects of histamine, a chemical in your body responsible for allergy and cold symptoms like a runny nose and sneezing.
Chlorpheniramine also affects certain chemicals in the brain, leading to a sedative effect. This is why you feel so tired and have trouble focusing, especially if you took it first thing in the morning.
Important Safety Warning: Because Sinarest can cause significant drowsiness and impair your focus, you must exercise extreme caution when taking it during the day.
Do not drive, operate heavy machinery, or engage in any activity that requires mental alertness until you know exactly how the medication affects you. If the drowsiness is severely impacting your daily life, you should speak with your healthcare provider. They may recommend:
Taking the medicine only at night.
Switch to a different cold or allergy medicine that contains a non-sedating antihistamine.