Last updated on RxList: 11/18/2020
Sesquient Side Effects Center

What Is Sesquient?

Sesquient (fosphenytoin sodium) is an anticonvulsant used to treat generalized tonic-clonic status epilepticus in adult patients and to prevent and treat seizures occurring during neurosurgery in adult patients and for short-term substitution for oral phenytoin in patients 2 years of age and older.

What Are Side Effects of Sesquient?

Side effects of Sesquient include:

Antiepileptic drugs such as Sesquient should not be abruptly discontinued because of the possibility of increased seizure frequency, including status epilepticus.

Dosage for Sesquient

The loading dose of Sesquient for status epilepticus in adults is 15 mg PE/kg to 20 mg PE/kg at a rate of 100 mg PE/minute to 150 mg PE/minute. For non-emergent loading and maintenance dosing the adult loading dose of Sesquient is 10 mg PE/kg to 20 mg PE/kg given intravenously; the initial maintenance dose is 4 mg PE/kg to 6 mg PE/kg/day in divided doses. The pediatric loading dose of Sesquient is 10 mg PE/kg to 15 mg PE/kg given intravenously; the initial maintenance dose is 2 mg PE/kg to 4 mg PE/kg every 12 hours.

Sesquient In Children

Safety and effectiveness of Sesquient in pediatric patients for the treatment of generalized tonic-clonic status epilepticus and prevention and treatment of seizures occurring during neurosurgery have not been established.

The safety and effectiveness of Sesquient for the short-term substitution of oral phenytoin have been established in pediatric patients 2 years of age and older.

Safety of Sesquient for short-term substitution for oral phenytoin in patients below the 2 years of age has not been established.

What Drugs, Substances, or Supplements Interact with Sesquient?

Sesquient may interact with other medicines such as:

Tell your doctor all medications and supplements you use.

Sesquient During Pregnancy and Breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant before using Sesquient; it may harm a fetus. There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as Sesquient, during pregnancy. It is unknown if Sesquient passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Sesquient (fosphenytoin sodium) Injection, for Intravenous Use Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Sesquient Consumer Information

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include: skin rash, fever, swollen glands, flu-like symptoms, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes. This reaction may occur several weeks after you began using fosphenytoin.

Call your doctor at once if you have:

  • very slow heartbeats, shortness of breath;
  • a light-headed feeling, like you might pass out;
  • confusion, unusual thoughts or behavior;
  • a tingling or burning sensation;
  • easy bruising, unusual bleeding;
  • purple discoloration of your skin around the IV needle;
  • sudden weakness or ill feeling, fever, chills, sore throat, mouth sores, red or swollen gums, trouble swallowing; o
  • low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Common side effects may include:

  • dizziness, drowsiness;
  • unusual or involuntary eye movements;
  • vomiting;
  • itching; or
  • problems with balance or muscle movement.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Sesquient (Fosphenytoin Sodium Injection)


What Is Epilepsy? Symptoms, Causes, and Treatments See Slideshow
Sesquient Professional Information


The following serious adverse reactions are described elsewhere in the labeling:

  • Cardiovascular Risk Associated with Rapid Infusion [see WARNINGS AND PRECAUTIONS]
  • Withdrawal Precipitated Seizure, Status Epilepticus [see WARNINGS AND PRECAUTIONS]
  • Serious Dermatologic Reactions [see WARNINGS AND PRECAUTIONS]
  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see WARNINGS AND PRECAUTIONS]
  • Hypersensitivity [see WARNINGS AND PRECAUTIONS]
  • Hepatic Injury [see WARNINGS AND PRECAUTIONS]
  • Hematopoietic Complications [see WARNINGS AND PRECAUTIONS]
  • Sensory Disturbances [see WARNINGS AND PRECAUTIONS]
  • Local Toxicity (Including Purple Glove Syndrome) [see WARNINGS AND PRECAUTIONS]
  • Exacerbation of Porphyria [see WARNINGS AND PRECAUTIONS]
  • Teratogenicity and Other Harm to the Newborn [see WARNINGS AND PRECAUTIONS]
  • Hyperglycemia [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The more important adverse clinical reactions caused by the intravenous (IV) use of SESQUIENT or phenytoin are cardiovascular collapse and/or central nervous system depression. Hypotension can occur when either drug is administered rapidly by the IV route. The rate of administration is very important; for SESQUENT, the rate for adult patients should not exceed 150 mg PE/min. The rate of administration of SESQUIENT in pediatric patients is limited to 0.4 mg PE/kg/min because the safety of IV administration of the betadex sulfobutyl ether sodium ingredient in SESQUIENT at a faster rate has not been established [see WARNINGS AND PRECAUTIONS and Use In Specific Populations].

The data presented below were obtained from a formulation of fosphenytoin injection that does not contain betadex sulfobutyl ether sodium [see Clinical Studies].

The adverse reactions most commonly observed with the use of fosphenytoin injection in clinical trials were nystagmus, dizziness, pruritus, somnolence, and ataxia. With one exception, these reactions are commonly associated with the administration of IV phenytoin. Pruritus, however, was seen much more often following fosphenytoin injection administration compared to phenytoin injection. These reactions were dose and rate related; most alert patients (41 of 64; 64%) administered doses of ≥15 mg PE/kg at 150 mg PE/min experienced discomfort of some degree. These sensations, generally described as itching, burning, or tingling, were usually not at the infusion site. The location of the discomfort varied with the groin mentioned most frequently as a site of involvement. The paresthesia and pruritus were transient events that occurred within several minutes of the start of infusion and generally resolved within 10 minutes after completion of fosphenytoin infusion. Some patients experienced symptoms for hours. These reactions did not increase in severity with repeated administration. Concurrent adverse events or clinical laboratory change suggesting an allergic process were not seen [see WARNINGS AND PRECAUTIONS]. Approximately 2% of the 859 patients who received fosphenytoin injection in premarketing clinical trials discontinued treatment because of an adverse event. The adverse events most commonly associated with withdrawal were pruritus (0.5%), hypotension (0.3%), and bradycardia (0.2%).

Dose And Rate Dependency Of Adverse Reactions Following IV Fosphenytoin Injection

The incidence of adverse reactions tended to increase as both dose and infusion rate increased. In particular, at doses of ≥15mg PE/kg and rates ≥150 mg PE/min, transient pruritus, tinnitus, nystagmus, somnolence, and ataxia occurred 2 to 3 times more often than at lower doses or rates.

Incidence In Controlled Clinical Trials -IV Administration To Adult Patients With Epilepsy Or Neurosurgical Patients

Table 4 lists adverse reactions that occurred in at least 2% of adult patients treated with IV fosphenytoin at the maximum dose and rate in a randomized, double-blind, controlled clinical trial where the rates for phenytoin and fosphenytoin administration would have resulted in equivalent systemic exposure to phenytoin.

TABLE 4. Adverse Reaction Incidence Following IV Administration at the Maximum Dose and Rate to Adult Patients with Epilepsy or Neurosurgical Patients (Events in at Least 2% of Fosphenytoin-Treated Patients)

BODY SYSTEMIV Fosphenytoin
IV Phenytoin1
Adverse Event
  Pelvic Pain40
  Back Pain20
  Tongue Disorder40
  Dry Mouth45
  Extrapyramidal Syndrome40
  Brain Edema25
  Taste Perversion30
1 The study was not designed to assess comparative safety.

Incidence In Clinical Trials -IV Administration To Pediatric Patients

The overall incidence of adverse reactions and the types of adverse reactions seen were similar among children and adults treated with fosphenytoin injection. In an open-label, safety, tolerability, and pharmacokinetic study of fosphenytoin in pediatric patients (including age 2 through age 16), the following adverse reactions occurred at a frequency of at least 5% in 96 patients treated with IV fosphenytoin: vomiting (21%), nystagmus (18%), ataxia (10%), fever (8%), nervousness (7%), pruritus (6%), somnolence (6%), hypotension (5%), and rash (5%).

Adverse Events During Clinical Trials In Adult And Pediatric Patients

Fosphenytoin injection has been administered to approximately 900 individuals during clinical trials. Adverse events seen at least twice are listed in the following, except those already included in previous tables and listings. Events are further classified within body system categories and enumerated in order of decreasing frequency using the following definitions: frequent adverse events are defined as those occurring in greater than 1/100 individuals; infrequent adverse events are those occurring in 1/100 to 1/1000 individuals.

Body as a Whole: Frequent: fever, injection-site reaction, infection, chills, face edema, injection-site pain; Infrequent: sepsis, injection-site inflammation, injection-site edema, injection-site hemorrhage, flu syndrome, malaise, generalized edema, shock, photosensitivity reaction, cachexia, cryptococcosis.

Cardiovascular: Frequent: hypertension; Infrequent: cardiac arrest, migraine, syncope, cerebral hemorrhage, palpitation, sinus bradycardia, atrial flutter, bundle branch block, cardiomegaly, cerebral infarct, postural hypotension, pulmonary embolus, QT interval prolongation, thrombophlebitis, ventricular extrasystoles, congestive heart failure.

Digestive: Frequent: constipation; Infrequent: dyspepsia, diarrhea, anorexia, gastrointestinal hemorrhage, increased salivation, liver function tests abnormal, tenesmus, tongue edema, dysphagia, flatulence, gastritis, ileus.

Endocrine: Infrequent: diabetes insipidus.

Hematologic and Lymphatic: Infrequent: thrombocytopenia, anemia, leukocytosis, cyanosis, hypochromic anemia, leukopenia, lymphadenopathy, petechia.

Laboratory Test Abnormality: Phenytoin (the active metabolite of SESQUIENT) may cause increased serum levels of glucose and alkaline phosphatase.

Metabolic and Nutritional: Frequent: hypokalemia; Infrequent: hyperglycemia, hypophosphatemia, alkalosis, acidosis, dehydration, hyperkalemia, ketosis.

Musculoskeletal: Frequent: myasthenia; Infrequent: myopathy, leg cramps, arthralgia, myalgia.

Nervous: Frequent: reflexes increased, speech disorder, dysarthria, intracranial hypertension, thinking abnormal, nervousness; Infrequent: confusion, twitching, Babinski sign positive, circumoral paresthesia, hemiplegia, hypotonia, convulsion, extrapyramidal syndrome, insomnia, meningitis, depersonalization, CNS depression, depression, hypokinesia, hyperkinesia, paralysis, psychosis, aphasia, emotional lability, coma, hyperesthesia, myoclonus, personality disorder, acute brain syndrome, encephalitis, subdural hematoma, encephalopathy, hostility, akathisia, amnesia, neurosis.

Respiratory: Frequent: pneumonia; Infrequent: pharyngitis, sinusitis, hyperventilation, rhinitis, apnea, aspiration pneumonia, asthma, dyspnea, atelectasis, cough increased, sputum increased, epistaxis, hypoxia, pneumothorax, hemoptysis, bronchitis.

Skin and Appendages: Frequent: rash; Infrequent: maculopapular rash, urticaria, sweating, skin discoloration, contact dermatitis, pustular rash, skin nodule.

Special Senses: Infrequent: visual field defect, eye pain, conjunctivitis, photophobia, hyperacusis, mydriasis, parosmia, ear pain, taste loss.

Urogenital: Infrequent: urinary retention, oliguria, dysuria, vaginitis, albuminuria, genital edema, kidney failure, polyuria, urethral pain, urinary incontinence, vaginal moniliasis.

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of fosphenytoin. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as a Whole: Anaphylaxis, angioedema [see WARNINGS AND PRECAUTIONS]

Laboratory Test Abnormality: Phenytoin or SESQUIENT may decrease serum concentrations of T4. It may also produce lower than normal values for dexamethasone or metyrapone tests. Phenytoin may also cause increased serum levels of gamma glutamyl transpeptidase (GGT).

Nervous System Disorders: Dyskinesia

Read the entire FDA prescribing information for Sesquient (Fosphenytoin Sodium Injection)


If you have had a seizure, it means you have epilepsy. See Answer

© Sesquient Patient Information is supplied by Cerner Multum, Inc. and Sesquient Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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