acetaminophen/guaifenesin (OTC)

Frequency Not Defined

Dizziness

Drowsiness

Headache

Dermatologic rash

Nausea

Vomiting

Anemia blood dyscrasias (neutropenia, pancytopenia, leukopenia)

Bilirubin and alkaline phosphatase may increase

Contraindications

Hypersensitivity

G-6-PD deficiency

Severe hepatic impairment

Cautions

Acetaminophen hepatotoxicity possible in chronic alcoholics following various dose levels; severe or recurrent pain or high or continued fever may indicate a serious illness; contained in many OTC products and combined use with these products may result in toxicity due to cumulative doses exceeding recommended maximum dose

Acetaminophen: Risk for rare, but serious skin reactions that can be fatal; these reactions include Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP); symptoms may include skin redness, blisters and rash

Guaifenesin is not for administration in persistent cough associated with chronic bronchitis, smoking, asthma, or accompanied with excessive secretions

Pregnancy category: C

Lactation: excreted in breast milk; use caution

Pregnant or breastfeeding patients should seek advice of health professional before using OTC drugs

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Acetaminophen blocks pain impulse generation peripherally & may inhibit the generation of prostaglandin in the CNS; reduces fever by inhibiting the hypothalamic heat-regulating center

Guaifenesin increases respiratory tract fluid secretions & helps to loosen phlegm & bronchial secretions

Pharmacokinetics

Acetaminophen

• Peak plasma time: 10-60 min (PO immediate release); 60-120 min (PO extended release); 6 hr (PO 500 mg tablet); 8 hr (PO 650 mg extended release tablet)
• Vd: 1 L/kg
• Protein binding: 10-25%
• Metabolism: Liver (microsomal enzyme systems); conjugation (glucuronic acid)
• Half-life: 1.25-3hr
• Excretion: Urine

Guaifenesin

• Half-Life: 1 hr
• Onset: 30 min
• Duration: 4-6 hr
• Metabolism: Liver
• Metabolite: b-(2-methoxyphenoxy) lactic acid
• Excretion: Urine