Phenyltoloxamine citrate is an antihistamine often added to other over-the-counter medications to intensify cough or pain relief. Antihistamines inhibit the release and actions of the immune system molecule, histamine, which is responsible for causing allergy symptoms such as runny nose and itchy eyes. Phenyltoloxamine citrate also has sedative and analgesic effects and potentiates the actions of codeine and acetaminophen. It is not a controlled substance.
Anticholinergic Syndrome
Many medications, including phenyltoloxamine citrate, are classified as anticholinergics. Drugs of this class block the actions of acetylcholine, which is a chemical messenger that signals to nerve and muscle cells. It is by this mechanism that phenyltoloxamine citrate suppresses coughing. At high doses, phenyltoloxamine citrate can cause anticholinergic syndrome, which is characterized by dizziness, headache, blurred vision, drowsiness, irregular heartbeat, dry mouth, tinnitus, movement disorders and constipation. A review in the November 2009 issue of "Clinical Geriatrics" states that elderly people are particularly susceptible to anticholinergics because of decreased acetylcholine levels and changes in metabolism.
Toxicity Studies
Despite its widespread use in medications, few toxicity studies have been conducted to determine the safety of phenyltoloxamine citrate. An older study published in the October 1953 issue of the "Journal of Pharmaceutical Sciences" reports that administration of up to 40 mg/kg of phenyltoloxamine citrate for one year did not cause overt toxicity in dogs.
Drug Interactions
As previously stated, other medications are classified as anticholinergics, and their effects are additive if taken in combination. The study in "Clinical Geriatrics" notes that over 600 different medications display anticholinergic properties, and just above 50 percent of the population uses a medication with anticholinergic properties on a regular basis. Additionally, the sedative effects of phenyltoloxamine citrate are additive to alcohol, other sedatives and tranquilizers.
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