Salonpas and Synthroid drug interactions - a phase IV clinical study of FDA data

Summary:

Drug interactions are reported among people who take Salonpas (menthol; methyl salicylate) and Synthroid (levothyroxine sodium). Common drug interactions include drug ineffective among females and benign prostatic hyperplasia among males.

The phase IV clinical study analyzes what interactions people have when they take Salonpas and Synthroid. It is created by eHealthMe based on reports of 14 people who take the same drugs from the FDA, and is updated regularly.

What is Salonpas?

Salonpas has active ingredients of menthol; methyl salicylate. eHealthMe is studying from 630 Salonpas users. Check the latest studies of Salonpas.

What is Synthroid?

Synthroid has active ingredients of levothyroxine sodium. It is often used in hypothyroidism. eHealthMe is studying from 249,198 Synthroid users. Check the latest studies of Synthroid.

On Jul, 27, 2026

14 people who take Salonpas and Synthroid together, and have interactions are studied.

Salonpas and Synthroid drug interactions.

What are the common drug interactions of Salonpas and Synthroid, by gender? *:

female:

Drug ineffective
Myocardial infarction (destruction of heart tissue resulting from obstruction of the blood supply to the heart muscle)
Application site pain
Application site pruritus (application site severe itching of the skin)
Bronchitis (inflammation of the mucous membrane in the bronchial tubes)
Death
Dehydration (dryness resulting from the removal of water)
Hyperhidrosis (abnormally increased sweating)
Infusion site extravasation (flow of (blood or lymph) from infusion site)
Infusion site haemorrhage (bleeding from infusion site)

male:

Benign prostatic hyperplasia (benign enlargement of the prostate)
Cardiac failure congestive
Dehydration (dryness resulting from the removal of water)
Dyspnoea (difficult or laboured respiration)
Pneumonia
Squamous cell carcinoma (a cancer of a kind of epithelial cell)

What are the common drug interactions of Salonpas and Synthroid, by age (0-1 to 60+)? *:

0-1:

n/a

2-9:

n/a

10-19:

n/a

20-29:

n/a

30-39:

n/a

40-49:

Drug ineffective

50-59:

n/a

60+:

Application site rash
Dehydration (dryness resulting from the removal of water)
Nausea (feeling of having an urge to vomit)
Pneumonia
Skin discolouration (change of skin colour)
Skin ulcer
Squamous cell carcinoma (a cancer of a kind of epithelial cell)
Vagus nerve disorder
Application site pain
Application site pruritus (application site severe itching of the skin)

What are the existing conditions these people have? *

Narcolepsy (brain's inability to regulate sleep-wake cycles normally): 3 people, 21.43%
Multiple Myeloma (cancer of the plasma cells): 2 people, 14.29%
Immunodeficiency Common Variable: 2 people, 14.29%
Thyroid Diseases: 1 person, 7.14%
Sinus Congestion (blockage of sinus): 1 person, 7.14%
Rheumatoid Arthritis (a chronic progressive disease causing inflammation in the joints): 1 person, 7.14%
Prostate Cancer: 1 person, 7.14%
Prolactinoma (benign tumour (adenoma) of the pituitary gland that produces a hormone called prolactin): 1 person, 7.14%
Pain: 1 person, 7.14%
Musculoskeletal Chest Pain (pain in chest muscle or nerve or bones): 1 person, 7.14%

* Approximation only. Some reports may have incomplete information.

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