Dissociation Between Free and Bound Phenytoin Levels in Presence of Valproate Sodium

Rodin, Ervin Y.; DeSousa, Garcia; Haidukewych, Dan; Lodhi, Rashid; Berchou, Richard

doi:10.1001/archneur.1981.00510040066011

Cited by 23 publications

(2 citation statements)

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“…Past reports have suggested that drug toxicity could be explained by an increased free fraction in the presence of therapeutic total PHT levels [4, 21,241. High interpatient and intrapatient free fraction variability, nonsystematic toxicity testing, and lack of statistical analysis make these studies difficult to compare with ours.…”

Section: Discussionmentioning

confidence: 99%

The clinical value of free phenytoin levels

Theodore

Price

et al. 1985

Annals of Neurology

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The relationship between total and free phenytoin levels and drug toxicity was studied in 80 patients. Twenty-four were taking phenytoin alone. Drug toxicity was assessed by a "blind" rater using an eight-point standardized scoring system. The mean free phenytoin fraction was 0.076 in patients taking phenytoin alone or phenytoin and carbamazepine and 0.11 in patients taking valproic acid (p less than 0.001). The free fraction did not change with the total level over the range tested (6.7 to 39.9 micrograms/ml total phenytoin). There was a strong correlation between free and total levels (r = 0.84). Both free (r = 0.59) and total (r = 0.49) phenytoin levels were positively correlated with the toxicity score. Only total phenytoin levels showed a weak positive correlation with decreasing seizure frequency. Our results suggest that routine free phenytoin level monitoring is not necessary in most clinical situations.

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Section: Discussionmentioning

confidence: 99%

The clinical value of free phenytoin levels

Theodore

Price

et al. 1985

Annals of Neurology

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“…It also must be noted, enzyme interactions can also affect serum drug concentrations when phenytoin and valproic acid are used in combination. This combination also leads to alterations in protein binding, with valproic acid displacing plasma bound phenytoin [29] , [30] , [31] . Given the complexity of this drug combination in addition to the pharmacokinetic complexities of malabsorptive states, it is imperative to follow serum drug concentrations when using phenytoin and valproic acid in combination.…”

Section: Practical Considerationsmentioning

confidence: 99%

Antiseizure Medication use in Gastric Bypass Patients and Other Post-Surgical Malabsorptive States

Brown

Rabinstein

Nystrom

et al. 2021

Epilepsy & Behavior Reports

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Highlights Patients with epilepsy undergoing bariatric surgery (or extensive intestinal resection for a different indication) should be followed by a multidisciplinary team including a pharmacist and a neurologist. ASM concentrations should be frequently checked before and after surgery. Upon discharge, ensure close follow up with a neurologist and pharmacist to monitor ASM levels. Extended release formulations should be avoided. Pharmacokinetic factors should be considered when selecting and adjusting ASMs.

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Pharmakokinetische Prinzipien und spezielle Pharmakokinetik der Antiarrhythmika

Jähnchen¹,

Trenk²

1983

Herzrhythmusstörungen

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Dissociation Between Free and Bound Phenytoin Levels in Presence of Valproate Sodium

Cited by 23 publications

References 10 publications

The clinical value of free phenytoin levels

The clinical value of free phenytoin levels

Antiseizure Medication use in Gastric Bypass Patients and Other Post-Surgical Malabsorptive States

Pharmakokinetische Prinzipien und spezielle Pharmakokinetik der Antiarrhythmika

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