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

Summary:

Drug interactions are reported among people who take Synthroid (levothyroxine sodium) and Nyquil (acetaminophen / dextromethorphan / doxylamine / pseudoephedrine). Common drug interactions include musculoskeletal stiffness among females and rash among males.

The phase IV clinical study analyzes what interactions people have when they take Synthroid and Nyquil. It is created by eHealthMe based on reports of 59 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 Nyquil?

Nyquil has active ingredients of acetaminophen / dextromethorphan / doxylamine / pseudoephedrine. It is often used in cold symptoms. eHealthMe is studying from 2,240 Nyquil users. Check the latest studies of Nyquil.

On Jun, 09, 2026

59 people who take Synthroid and Nyquil together, and have interactions are studied.

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

female:

Musculoskeletal stiffness (stiffness of the body's muscles, joints, tendons, ligaments and nerves)
Oral fungal infection
Oropharyngeal candidiasis (fungal infection of oropharynx)
Osteoarthritis (a joint disease caused by cartilage loss in a joint)
Pain
Rash
Road traffic accident
Swollen tongue (swelling of tongue)
Throat tightness
Viral upper respiratory tract infection

male:

Rash
Hypoaesthesia (reduced sense of touch or sensation)
Eye pain
Lacrimation decreased
Nasal dryness (dry nose)
Visual impairment
Abdominal pain upper
Androgen deficiency
Ankle fracture
Anxiety

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

0-1:

n/a

2-9:

n/a

10-19:

n/a

20-29:

Androgen deficiency
Ankle fracture
Anxiety
Bone disorder
Chronic obstructive pulmonary disease (a progressive disease that makes it hard to breathe)
Depression
Fall
Humerus fracture (injury to the upper arm bone)
Lower limb fracture
Lymphoma (cancer that begins in immune system cells)

30-39:

Infusion related reaction
Pneumonia
Rash
Respiratory disorder (respiratory disease)
Abdominal pain upper
Arthralgia (joint pain)
Back pain
Hyperuricaemia (level of uric acid in the blood that is abnormally high)
Periodontal disease (disease that attacks the gum and bone and around the teeth)
Affect lability (emotional incontinence)

40-49:

Arrhythmia (irregular heartbeat)
Chills (felling of cold)
Completed suicide (act of taking one's own life)
Fatigue (feeling of tiredness)
Heart rate increased
Myalgia (muscle pain)
Rash
Seizure (abnormal excessive or synchronous neuronal activity in the brain)
Tremor (trembling or shaking movements in one or more parts of your body)
Vomiting

50-59:

Abdominal compartment syndrome (increased pressure in abdomen)
Asthma
Chest pain
Coronavirus test positive
Death
Deep vein thrombosis (blood clot in a major vein that usually develops in the legs and/or pelvis)
Disease recurrence
Dysphonia (speech disorder attributable to a disorder of phonation)
Endometrial stromal sarcoma (endometrial tumour arising from the stroma (connective tissue))
Haematuria (presence of blood in urine)

60+:

Fatigue (feeling of tiredness)
Death
Nasopharyngitis (inflammation of the nasopharynx)
Constipation
Contusion (a type of hematoma of tissue in which capillaries)
Dysphagia (a condition in which swallowing is difficult or painful)
Ecchymosis (a discoloration of the skin resulting from bleeding underneath)
Erosive oesophagitis (acid reflux disease can cause tissue damage in the oesophagus over time)
Haematuria (presence of blood in urine)
Haemorrhage (bleeding)

What are the existing conditions these people have? *

Pain: 8 people, 13.56%
Rheumatoid Arthritis (a chronic progressive disease causing inflammation in the joints): 7 people, 11.86%
High Blood Pressure: 6 people, 10.17%
Multiple Myeloma (cancer of the plasma cells): 6 people, 10.17%
Gastroesophageal Reflux Disease (a condition in which stomach contents leak backward from the stomach into the oesophagus): 5 people, 8.47%
Nasal Congestion (blockage of the nasal passages usually due to membranes lining the nose becoming swollen from inflamed blood vessels): 5 people, 8.47%
Narcolepsy (brain's inability to regulate sleep-wake cycles normally): 5 people, 8.47%
Multiple Sclerosis (a nervous system disease that affects your brain and spinal cord. it damages the myelin sheath): 5 people, 8.47%
Thyroid Diseases: 4 people, 6.78%
Dyspnea (difficult or laboured breathing): 4 people, 6.78%

* Approximation only. Some reports may have incomplete information.

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