Synthroid and Dilantin-125 drug interactions - a phase IV clinical study of FDA data

Summary:

Drug interactions are reported among people who take Synthroid (levothyroxine sodium) and Dilantin-125 (phenytoin). Common drug interactions include visual acuity reduced among females and stevens-johnson syndrome among males.

The phase IV clinical study analyzes what interactions people have when they take Synthroid and Dilantin-125. It is created by eHealthMe based on reports of 40 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 249,202 Synthroid users. Check the latest studies of Synthroid.

What is Dilantin-125?

Dilantin-125 has active ingredients of phenytoin. It is often used in epilepsy. eHealthMe is studying from 2,213 Dilantin-125 users. Check the latest studies of Dilantin-125.

On Aug, 01, 2026

40 people who take Synthroid and Dilantin-125 together, and have interactions are studied.

Synthroid and Dilantin-125 drug interactions.

What are the common drug interactions of Synthroid and Dilantin-125, by gender? *:

female:

Visual acuity reduced (reduced clearness of vision)
Weight increased
Gingival disorder (gum disease)
Abasia (inability to walk)
Back disorder
Drug ineffective
Peripheral arterial occlusive disease (reproducible ischemic muscle pain)
Diabetes mellitus (diabetes, caused by a deficiency of the pancreatic hormone insulin)
Drug hypersensitivity
Hypersensitivity

male:

Stevens-johnson syndrome (an immune-complex-mediated hypersensitivity disorder. it ranges from mild skin and mucous membrane lesions to a severe)
Amnesia (deficit in memory caused by brain damage, disease, or psychological trauma)
Coordination abnormal (abnormal movement)
Fatigue (feeling of tiredness)
Muscle twitching
Sedation
Ischaemic stroke (stroke; caused by an interruption in the flow of blood to the brain)
Sensorimotor disorder (disease of sensory and motor function of brain)
Abasia (inability to walk)
Accident at work

What are the common drug interactions of Synthroid and Dilantin-125, by age (0-1 to 60+)? *:

0-1:

n/a

2-9:

Accident at work
Anticonvulsant drug level decreased
Asthenia (weakness)
Back injury
Coma (state of unconsciousness lasting more than six hours)
Convulsion (muscles contract and relax rapidly and repeatedly, resulting in an uncontrolled shaking of the body)
Drug toxicity
Dysuria (painful or difficult urination)
Fall
Haematuria (presence of blood in urine)

10-19:

Abnormal behaviour
Appetite decreased (decreased appetite occurs when you have a reduced desire to eat)
Crying
Decreased activity
Difficulty in walking
Fall
Hallucination (an experience involving the perception of something not present)
Irritability
Lethargy (tiredness)
Weakness

20-29:

Aggression
Insomnia (sleeplessness)
Thyroid carcinoma (cancer tumour of thyroid gland)

30-39:

Stevens-johnson syndrome (an immune-complex-mediated hypersensitivity disorder. it ranges from mild skin and mucous membrane lesions to a severe)
Toxic epidermal necrolysis (a rare, life-threatening skin condition that is usually caused by a reaction to drugs causes wide spread skin destruction)

40-49:

Aggression
Alopecia (absence of hair from areas of the body)
Blood prolactin increased
Cerebral cyst (fluid filled tumour of brain)
Chest pain
Diabetes mellitus (diabetes, caused by a deficiency of the pancreatic hormone insulin)
Drug ineffective
Emotional disorder
Gingival disorder (gum disease)
Gingival hyperplasia (overgrowth of gums)

50-59:

Stevens-johnson syndrome (an immune-complex-mediated hypersensitivity disorder. it ranges from mild skin and mucous membrane lesions to a severe)
Urinary retention (the inability to completely or partially empty the bladder)
Amnesia (deficit in memory caused by brain damage, disease, or psychological trauma)
Balance disorder
Tremor (trembling or shaking movements in one or more parts of your body)
Anxiety
Cerebellar ataxia (loss of coordination)
Cerebellar atrophy (degeneration of the section of the brain responsible for balance, voluntary muscle movements)
Cognitive disorder (mental health disorders affects learning, memory, perception, and problem solving)
Dysarthria (speech disorder)

60+:

Anticonvulsant drug level decreased
Neuropathy peripheral (surface nerve damage)
Back disorder
Brain injury
Convulsion (muscles contract and relax rapidly and repeatedly, resulting in an uncontrolled shaking of the body)
Head injury
Joint injury
Peripheral arterial occlusive disease (reproducible ischemic muscle pain)
Drug ineffective
Gingival disorder (gum disease)

What are the existing conditions these people have? *

Convulsion (muscles contract and relax rapidly and repeatedly, resulting in an uncontrolled shaking of the body): 17 people, 42.50%
Thyroid Diseases: 7 people, 17.50%
High Blood Cholesterol: 6 people, 15.00%
Lennox-Gastaut Syndrome (epilepsy characterized by frequent seizures and different seizure types): 3 people, 7.50%
High Blood Pressure: 3 people, 7.50%
Stroke (sudden death of a portion of the brain cells due to a lack of oxygen): 3 people, 7.50%
Heart Rate Irregular: 3 people, 7.50%
Stress And Anxiety: 3 people, 7.50%
Asthma: 3 people, 7.50%
Seizures (abnormal excessive or synchronous neuronal activity in the brain): 2 people, 5.00%

* Approximation only. Some reports may have incomplete information.

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