Product Information

Registration Status: Active

DILANTIN CAPSULE 30mg is approved to be sold in Singapore with effective from 1991-05-22. It is marketed by PFIZER PTE LTD, with the registration number of SIN06056P.

This product contains Phenytoin 30mg in the form of CAPSULE. It is approved for ORAL use.

This product is manufactured by Pfizer Pharmaceuticals LLC in UNITED STATES.

It is a Prescription Only Medicine that can only be obtained from a doctor or a dentist, or a pharmacist with a prescription from a Singapore-registered doctor or dentist.



An anticonvulsant that is used in a wide variety of seizures. It is also an anti-arrhythmic and a muscle relaxant. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channels, active transport, and general membrane stabilization. The mechanism of its muscle relaxant effect appears to involve a reduction in the sensitivity of muscle spindles to stretch. Phenytoin has been proposed for several other therapeutic uses, but its use has been limited by its many adverse effects and interactions with other drugs. [PubChem]


For the control of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery.

Mechanism of Action

Phenytoin acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. By promoting sodium efflux from neurons, phenytoin tends to stabilize the threshold against hyperexcitability caused by excessive stimulation or environmental changes capable of reducing membrane sodium gradient. This includes the reduction of post-tetanic potentiation at synapses. Loss of post-tetanic potentiation prevents cortical seizure foci from detonating adjacent cortical areas.


Bioavailability 70-100% oral, 24.4% rectal. Rapid rate of absorption with peak blood concentration expected in 1½ to 3 hours.
Primarily hepatic. The majority of the dose (up to 90%) is metabolized to 5-(4'-hydroxyphenyl)-5-phenylhydantoin (p-HPPH). This metabolite undergoes further glucuronidation and is excreted into the urine. CYP2C19 and CYP2C9 catalyze the aforementioned reaction.


Oral, mouse: LD50 = 150 mg/kg; Oral, rat: LD50 = 1635 mg/kg. Symptoms of overdose include coma, difficulty in pronouncing words correctly, involuntary eye movement, lack of muscle coordination, low blood pressure, nausea, sluggishness, slurred speech, tremors, and vomiting.

Active Ingredient/Synonyms

5,5-Diphenyl-imidazolidine-2,4-dione | 5,5-diphenylimidazolidine-2,4-dione | 5,5-diphenyltetrahydro-1H-2,4-imidazoledione | 5,5-Diphenyltetrahydro-1H-2,4-imidazoledione | Diphenylhydantoin | Fenitoina | Phentytoin | Phenytoine | Phenytoinum | Phenytoin |

Source of information: Drugbank (External Link). Last updated on: 3rd July 18. *Trade Name used in the content below may not be the same as the HSA-registered product.


  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank