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

Summary:

Drug interactions are reported among people who take Synthroid (levothyroxine sodium) and Doryx (doxycycline hyclate). Common drug interactions include papillary thyroid cancer among females and juvenile myoclonic epilepsy among males.

The phase IV clinical study analyzes what interactions people have when they take Synthroid and Doryx. It is created by eHealthMe based on reports of 29 people who take the same drugs from the FDA, and is updated regularly.

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.

What is Doryx?

Doryx has active ingredients of doxycycline hyclate. It is often used in acne. eHealthMe is studying from 901 Doryx users. Check the latest studies of Doryx.

On Jul, 14, 2026

29 people who take Synthroid and Doryx together, and have interactions are studied.

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

female:

Papillary thyroid cancer
Rash erythematous (redness of the skin)
Rash macular (small, flat red spots)
Skin discolouration (change of skin colour)
Skin exfoliation (removal of the oldest dead skin cells)
Suicidal ideation
Transient ischaemic attack (a transient episode of neurologic dysfunction caused by ischemia (loss of blood flow))
Weight increased
Abdominal tenderness
Abscess (pus)

male:

Juvenile myoclonic epilepsy (childhood epilepsy occurring early in morning affecting 12 to 18 years)
Abdominal pain
Atrioventricular block first degree (heart block first degree)
Benign prostatic hyperplasia (benign enlargement of the prostate)
Bladder obstruction
Blister (small pocket of fluid within the upper layers of the skin caused by forceful rubbing (friction), burning, freezing, chemical exposure)
Blood potassium increased
Cardiac disorder
Cardiac failure congestive
Cardiac murmur (an heart sound in valve abnormality)

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

0-1:

n/a

2-9:

n/a

10-19:

Juvenile myoclonic epilepsy (childhood epilepsy occurring early in morning affecting 12 to 18 years)
Antiendomysial antibody positive

20-29:

Papillary thyroid cancer
Suicidal ideation
Aspartate aminotransferase increased
Autoimmune thyroiditis (form of thyroiditis associated with an autoimmune disease)
Balance disorder
C-reactive protein increased
Cerebrovascular accident (sudden death of some brain cells due to lack of oxygen when the blood flow to the brain is impaired by blockage or rupture)
Depression
Diarrhoea
General physical health deterioration (weak health status)

30-39:

n/a

40-49:

Chest pain
Erosive oesophagitis (acid reflux disease can cause tissue damage in the oesophagus over time)
Pharyngolaryngeal pain
Transient ischaemic attack (a transient episode of neurologic dysfunction caused by ischemia (loss of blood flow))

50-59:

Application site pain
Bone pain
Constipation
Cough
Cyst (a closed sac)
Dyspepsia (indigestion)
Gastrointestinal disorder (functional problems of gastrointestinal tract)
Haematochezia (passage of stools containing blood)
Hiccups (an involuntary spasm of the diaphragm and respiratory organs, with a sudden closure of the glottis and a sound like a cough)
Libido increased (increased sexual urge to have sex)

60+:

Arteriosclerosis (thickening and hardening of arteries)
Arthralgia (joint pain)
Hypertension (high blood pressure)
Ill-defined disorder
Injury
Insomnia (sleeplessness)
Intermittent claudication
Ischaemia (insufficient supply of blood to an organ, usually due to a blocked artery)
Neuropathy peripheral (surface nerve damage)
Peripheral vascular disorder

What are the existing conditions these people have? *

Narcolepsy (brain's inability to regulate sleep-wake cycles normally): 6 people, 20.69%
Lyme Disease (a bacterial infection that is spread to humans by infected ticks): 4 people, 13.79%
Type 2 Diabetes: 2 people, 6.90%
Lung Neoplasm Malignant (cancer tumour of lung): 2 people, 6.90%
High Blood Pressure: 2 people, 6.90%
Growth Hormone Deficiency: 2 people, 6.90%
Depression: 2 people, 6.90%
Cataplexy (loss of muscle tone accompanied by full conscious awareness): 2 people, 6.90%

* Approximation only. Some reports may have incomplete information.

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