ACMT Toxicology Visual Pearl: The Bark with Some Bite

1. Aspirin

Background

The photo shows a weeping willow, a member of the Salix genus of trees. Willow tree bark contains salicin from which aspirin (acetylsalicylic acid) can be derived.

For over 3500 years, willow bark has been used as a traditional medicine to treat fevers and pain [1]. The active compound, salicin, is metabolized to salicylic acid in the body providing analgesic and antipyretic effects [2]. In 1897, Dr. Felix Hoffman modified salicylic acid and created acetylsalicylic acid (aspirin), now the most-used drug in the world due to its role in preventing cardiovascular and cerebrovascular disease [1].

How can people become poisoned with willow bark?

• Willow tree bark extract has been used as an herbal supplement for chronic lower back pain, joint pain, osteoarthritis, sports performance, and weight loss [3].
• Willow tree bark supplements are available as tablets, tinctures, powders, or tea.
• Cases of toxicity have been reported following ingestion of supplements as well as ingestion of willow bark tea [4,5].
• However, most adverse reactions from willow bark supplements have been associated with people who have aspirin allergies, with numerous cases of anaphylaxis [6].

How does willow bark toxicity present? [7]

• Toxicity from salicin mirrors toxicity from aspirin (salicylism) in its clinical presentation.
• One study shows that ingestion of 240 mg of salicin in willow bark tablets produced salicylate levels equivalent to 87 mg of acetylsalicylic acid, therefore serum salicylate levels will be detectable following ingestion [8].
• Salicylate has a direct effect on the respiratory center of the medulla causing tachypnea.
• Tinnitus, nausea, vomiting, and abdominal pain are common.
• With severe toxicity, patients can have altered mental status, seizures, hyperthermia, and pulmonary edema.
• Further information on the diagnosis and treatment of salicylate toxicity

Bedside Pearls

• Willow tree bark (Salix genus) contains salicin, which is metabolized in the body to salicylic acid.
• Ingestion of willow bark supplements can cause salicylism.
• Patients who have an aspirin allergy should avoid willow tree bark supplements, extracts, or teas.