Mucinex | Pharmacology Mentor

Generic Name

Mucinex

Guaifenesin, the active ingredient, is an expectorant that increases the volume and reduces the viscosity of mucus in the airways.
It enhances the movement of water into mucus through osmotic mechanisms, loosening secretions and facilitating cough clearance.
Improves mucociliary clearance and reduces the effort required for productive coughs.

Absorption: Rapid oral absorption; peak plasma concentrations in 1–2 h.
Distribution: Widely distributes with a mean volume of distribution ~60 L.
Metabolism: Primarily hydrolyzed to inactive metabolites; minor CYP450 involvement.
Elimination: Renal excretion; half‑life 2–4 h (extended‑release formulations ~12 h).
Drug interactions: Minimal; no clinically significant CYP450 inhibition or induction.

Short‑term relief of bronchitis, asthma, sinusitis, and upper/lower respiratory tract infections involving thick, copious mucus.
*Adjunctive* therapy to facilitate cough clearance in patients with productive cough.

Contraindicated in patients with known hypersensitivity to guaifenesin.
Use cautiously in renal impairment: reduced clearance may increase exposure.
Not recommended for infants <4 weeks or children <4 years without pediatric formulation.
Warnings: Rare cases of allergic dermatitis or urticaria; discontinue if rash or angioedema develops.

Age/Weight	Formulation	Dose	Frequency	Notes
Adults (≥18 yrs)	600 mg tablets	600 mg	q6h PRN (max 2400 mg/day)	2‑hour interdose interval
Adults	1200 mg extended‑release (ER)	1200 mg	q12h	8‑hour interdose interval reduces peak‑trough fluctuation
Children (≥4 yrs)	60 mg/5 mL syrup	5 mL (≈600 mg)	q6h PRN	Adjust per label
Geriatrics	Same as adults	600 mg	q6h PRN	Monitor renal function

• Take with food to minimize mild GI upset.
• Oral extended‑release formulation designed for 12‑hour coverage.

Common: Nausea, vomiting, abdominal discomfort, dry mouth.
Serious: Hypersensitivity reactions (rash, hives, angioedema), drug‑induced photosensitivity (rare).
Rare: CNS disturbances (headache, dizziness) reported at high doses.

Renal function: Serum creatinine and BUN for patients with CKD.
Allergic symptoms: Monitor for rash or breathing difficulty.
Efficacy: Frequency and force of cough, sputum quantity/colour.
Adverse effects: Gastro‑intestinal tolerability, especially with higher doses.

Maximize efficacy by timing doses 4–6 h apart; avoid exceeding the daily limit.
Extended‑release offers better adherence and sustained relief with fewer gastrointestinal side effects.
Not a bronchodilator: Use in conjunction with inhaled beta‑agonists for symptomatic relief in asthmatic patients.
Use with caution in patients on ACE inhibitors – both can trigger cough; monitor for additive cough severity.
For pediatric use, always use the syrup formulation and dose by weight; avoid tablets in children under 12 yrs.
Patients with severe renal impairment should use dose adjustment or consider alternative mucolytic agents (e.g., acetylcysteine) if available.

*Reference*: UpToDate, Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed.