Phenylephrine

Phenylephrine is a non-specific adrenergic agonist that selectively actives alpha-adrenoceptors, with minimal agonist activity at beta and dopamine receptors. It promotes vasoconstriction resulting in an increase in blood pressure that can lead to an increase heart rate. Phenylephrine is a synthetic analogue to norepinephrine, a neurotransmitter produced at the endings of postganglionic sympathetic neurons. Both phenylephrine and norepinephrine interact with adrenoceptors – a group of cell surface bound receptors which can be connected to intracellular signaling routes. There are three types, alpha-1, alpha-2 adrenoceptors, and beta, they are all connected to each other through intracellular 2nd messenger loops.
The drug is commonly present in over-the-counter decongestant nose drops and is used for relief from nasal/sinus congestion caused due to allergies, colds, or sinusitis; it does not treat the runny nose itself. Phenylephrine works rapidly by narrowing the blood vessels thus reducing swelling and congestion in the nasal passages so that one can breathe more effortlessly.
However it is not advisable for use in people with heart disease/high blood pressure or overage use, as it may lead to cardiovascular issues like increased heart palpitations, headaches due to increase in blood pressure can occur. Therefore, it important to consult with a healthcare providers before using it.