06-25-18 How much muscle rub is too much?

Toxicology Question of the Week

June 25, 2018

How much muscle rub is too much?

I recently noticed a muscle rub that was made in Thailand.   All the info is written in Thai, except for the active ingredients that include 31% methyl salicylate.

Methyl Salicylate can be found in many topical products used for minor aches and pains of the muscle and joints. These products include Tiger Balm®, Bengay®, Icy Hot®, and various brands of wintergreen oil – to name a few.  Methyl salicylate is also known as oil of wintergreen and is extremely toxic.  For a 10kg child, a lethal dose of pure oil of wintergreen is 5mL, which contains 5 grams of methyl salicylate, or 7.5 grams of Aspirin.

These topical products are intended for dermal application in adults only. Multiple applications or application to large areas of the body, application to broken skin, or application to children can cause serious salicylate toxicity. Acute symptoms of salicylate toxicity include nausea, vomiting, tinnitus, tachypnea, and confusion and typically occur within two hours of dermal application. Serious life-threatening symptoms can occur within six hours and include respiratory alkalosis, metabolic acidosis, cerebral edema, and death. Treatment is based on salicylate concentration and clinical signs/symptoms of poisoning.

Products containing 30% methyl salicylate are rarely responsible for poisoning when used in the intended manner as skin absorption is slow.1 After 30 min of contact 1.5 to 2% is absorbed, and after 10 hours of exposure 12 to 20% is systemically absorbed.1 Heat, occlusive dressings, young age, inflammation, and psoriasis can all also increase absorption.1

If you have a patient poisoned with salicylates, please call the Tennessee Poison Center with questions and concerns. An experienced specialist in poison information is ready to take your call 24/7.

This Question was prepared by: Donna Sainato, RN, SPI

1. Nelson L, Lewin N, and Howland M et al. Goldfrank's Toxicologic Emergencies. New York: McGraw-Hill, 2014. Internet resource.

I am interested in any questions you would like answered in the Question of the Week.  Please email me with any suggestion at donna.seger@vanderbilt.edu

Donna Seger, MD

Medical Director

Tennessee Poison Center

www.tnpoisoncenter.org

Poison Help Hotline: 1-800-222-1222

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