Caffeine (30mg) + Diphenhydramine (25mg) + Paracetamol (500mg) + Phenylephrine (5mg) (Medical Monograph)

Overview

A fixed-dose combination (FDC) medication primarily indicated for the symptomatic relief of the common cold, allergic rhinitis, and sinusitis. It combines an analgesic-antipyretic (Paracetamol), a first-generation sedating antihistamine (Diphenhydramine), a mild stimulant (Caffeine), and a nasal decongestant (Phenylephrine). This combination targets multiple symptoms simultaneously: fever, pain, nasal congestion, sneezing, and rhinorrhea, while caffeine is added to counteract the drowsiness caused by diphenhydramine.

Paracetamol: Acts centrally by inhibiting cyclooxygenase (COX), particularly the COX-2 isoform, and modulates the endogenous cannabinoid system, leading to analgesic and antipyretic effects with weak anti-inflammatory activity. Diphenhydramine: Competitively antagonizes histamine at the H1 receptor, reducing symptoms of allergy like sneezing, itching, and rhinorrhea. Its anticholinergic properties contribute to drying of secretions and sedation. Phenylephrine: A selective alpha-1 adrenergic receptor agonist causing vasoconstriction in the nasal mucosa, reducing blood flow and edema, thus relieving nasal congestion. Caffeine: Non-selective adenosine receptor antagonist (A1 and A2A), leading to CNS stimulation, reduced perception of fatigue, and mild bronchodilation. It may also enhance the analgesic effect of paracetamol.