Phenytoin vs. Phenytoin Sodium

Attribute	Phenytoin	Phenytoin Sodium
Chemical Formula	C15H12N2O2	C15H11N2NaO2
Molecular Weight	252.27 g/mol	274.27 g/mol
Drug Class	Anticonvulsant	Anticonvulsant
Brand Names	Dilantin, Phenytek	Dilantin Sodium, Phenytek
Administration	Oral, Injectable	Oral, Injectable
Indications	Epilepsy, Seizures	Epilepsy, Seizures
Availability	Generic	Generic
Half-life	22-36 hours	22-36 hours
Route of Elimination	Primarily renal	Primarily renal

Introduction

Phenytoin and Phenytoin Sodium are both antiepileptic drugs commonly used to treat various types of seizures. While they share similarities in terms of their mechanism of action and therapeutic effects, there are important differences between the two medications that should be considered when prescribing or administering them. This article aims to compare the attributes of Phenytoin and Phenytoin Sodium, highlighting their pharmacokinetics, formulations, indications, side effects, and potential drug interactions.

Pharmacokinetics

Phenytoin is a highly lipophilic compound that is poorly soluble in water. It is rapidly absorbed after oral administration, with peak plasma concentrations achieved within 1-3 hours. The absorption of Phenytoin Sodium, on the other hand, is more predictable due to its higher solubility in water. Phenytoin is extensively bound to plasma proteins, primarily albumin, while Phenytoin Sodium has a lower protein binding capacity. Both drugs undergo hepatic metabolism, but Phenytoin Sodium is metabolized more slowly, resulting in a longer half-life compared to Phenytoin.

Formulations

Phenytoin is available in various formulations, including immediate-release capsules, chewable tablets, and oral suspension. It can also be administered intravenously in a solution containing propylene glycol. Phenytoin Sodium, on the other hand, is primarily available as an injectable solution for intravenous use. The different formulations of Phenytoin allow for flexibility in dosing and route of administration, depending on the patient's needs and clinical situation.

Indications

Both Phenytoin and Phenytoin Sodium are indicated for the treatment of generalized tonic-clonic seizures and complex partial seizures. Additionally, they can be used as prophylaxis for seizures during neurosurgery or in patients at risk of developing seizures. Phenytoin Sodium, due to its intravenous formulation, is often preferred in emergency situations where rapid control of seizures is necessary. Phenytoin, with its various oral formulations, is commonly used for long-term maintenance therapy.

Side Effects

Phenytoin and Phenytoin Sodium share similar side effects, although the severity and frequency may vary. Common side effects include dizziness, drowsiness, ataxia, and gastrointestinal disturbances. Both medications can also cause more serious adverse effects, such as Stevens-Johnson syndrome, hepatotoxicity, and hematological abnormalities. However, Phenytoin Sodium has been associated with a higher incidence of local injection site reactions and cardiovascular effects, such as hypotension and arrhythmias, due to its intravenous administration.

Drug Interactions

Phenytoin and Phenytoin Sodium are known to interact with numerous medications, including other antiepileptic drugs, oral contraceptives, and warfarin. Phenytoin, being extensively metabolized by hepatic enzymes, can induce or inhibit the metabolism of other drugs, leading to potential therapeutic failures or toxicities. Phenytoin Sodium, due to its intravenous administration, may have fewer drug interactions compared to Phenytoin, as it bypasses the gastrointestinal tract and first-pass metabolism.

Conclusion

Phenytoin and Phenytoin Sodium are both valuable antiepileptic drugs with similar therapeutic effects. However, their pharmacokinetic properties, formulations, indications, side effects, and drug interactions differ, making them suitable for different clinical scenarios. Healthcare professionals should carefully consider these attributes when selecting the appropriate medication for their patients, taking into account factors such as route of administration, urgency of seizure control, and potential drug interactions. By understanding the unique characteristics of Phenytoin and Phenytoin Sodium, healthcare providers can optimize the management of epilepsy and improve patient outcomes.