Phenytoin is a first-line antiepileptic drug with narrow therapeutic range and follows non-linear pharmacokinetics. Pharmacokinetics of phenytoin have been studied in plasma matrix before, however, there were several disadvantages. This study aimed to obtain partial validation data of the analytical method and the pharmacokinetic profile of phenytoin in Dried Blood Spot (DBS) of six healthy subjects. DBS has the advantage of only requiring small sample volumes and could be transported more efficiently. Phenytoin along with carbamazepine as the chosen internal standard was analyzed with a reversed-phase high performance-liquid chromatography system and a photodiode array detector at 205 nm. The results of partial validation, which evaluated the linearity, within-run accuracy, and precision, were within the criteria acceptance range. The pharmacokinetic profile showed that average AUC0-t was 83.81 ± 37.32 μg.h/mL and AUC0-∞ was 83.65 ± 38.89 μg.h/mL with an average ratio of 93%. Previous study quantifying phenytoin in the plasma matrix found the average AUC0-t was 39.41 ± 8.57 µg.h/mL and AUC0-∞ was 42.94 ± 9.55 µg.h/mL. Despite the difference between parameters of phenytoin analyzed in DBS and plasma matrices, the pharmacokinetic profiles obtained from both matrices were similar indicated by comparable concentration-time curves, thus, proving that DBS matrix can be used interchangeably with the plasma matrix as a more comfortable and effective alternative to phenytoin quantification in blood.

We developed a reliable high-performance liquid chromatographic analysis method using a relative molar sensitivity (RMS) technique that does not require an authentic, identical reference analyte material to quantify blood serum carbamazepine, phenytoin, voriconazole, lamotrigine, meropenem, mycophenolic acid, linezolid, vancomycin, and caffeine levels for routine blood concentration measurements. Carbamazepine and caffeine were also used as non-analyte reference materials to calculate the RMS of each analyte. The RMS was calculated from the ratio of the slope of the calibration equation (analyte/non-analyte reference material), then used to quantify analytes in control serum samples spiked with carbamazepine, phenytoin, voriconazole, meropenem, mycophenolic acid, linezolid or vancomycin. In addition, the concentrations of these six drugs in control serum samples determined by the proposed RMS method agreed well with that obtained using a conventional method. The proposed RMS method is a promising tool for the clinical determination of nine drugs, given the accuracy, precision, and efficiency of quantifying these analytes.

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Phenytoin is a commonly prescribed antiepileptic medication for the prevention and treatment of tonic-clonic or partial seizures. Thrombocytopenia is a rare and serious adverse effect of phenytoin. This case report presents the case of a patient with severe thrombocytopenia induced by phenytoin for the treatment of tonic-clonic seizures. A 63-year-old male received 300 mg/day of phenytoin for the treatment of tonic-clonic seizures. Seven days after receiving the first dose of phenytoin, he was diagnosed with severe thrombocytopenia (platelet count 44 x 109/L) without hemorrhage. Phenytoin was discontinued, and seizures were controlled with levetiracetam. Seven days after stopping phenytoin, his daily platelet count improved from 44 to 177 x 109/L. The Naranjo algorithm score of 7 was at a probable level for phenytoin-induced thrombocytopenia. Thrombocytopenia is a serious adverse drug reaction that can result in life-threatening bleeding. Phenytoin-induced thrombocytopenia commonly begins 1-90 days after administration, and the recovery time is 3-21 days. The potential mechanism of phenytoin-induced thrombocytopenia is drug-induced immune thrombocytopenia. Drugs that enhance the concentration of phenytoin epoxide may be a contributing factor in phenytoin-induced thrombocytopenia. Phenytoin-induced thrombocytopenia is a rare but serious hematological complication. It should be recognized early, particularly in patients with a high risk of hemorrhage or concurrently with medications that increase phenytoin epoxide. Regularly consecutive complete blood count tests may be essential in order to detect an early decrease in platelet count in these patients.

Ultrathin molecularly imprinted polymer (MIP) films were deposited on the surfaces of ZnO nanorods (ZNRs) and nanosheets (ZNSs) by electropolymerization to afford extended-gate field-effect transistor sensors for detecting phenytoin (PHT) in plasma. Molecular imprinting efficiency was optimized by controlling the contents of functional monomers and the template in the precursor solution. PHT sensing was performed in plasma solutions with various concentrations by monitoring the drain current as a function of drain voltage under an applied gate voltage of 1.5 V. The reliability and reproducibility of the fabricated sensors were evaluated through a solution treatment process for complete PHT removal and PHT adsorption-removal cycling, while selectivity was examined by analyzing responses to chemicals with structures analogous to that of PHT. Compared with the ZNS/extracted-MIP sensor and sensors with non-imprinted polymer (NIP) films, the ZNR/extracted-MIP sensor showed superior responses to PHT-containing plasma due to selective PHT adsorption, achieving an imprinting factor of 4.23, detection limit of 12.9 ng/mL, quantitation limit of 53.0 ng/mL, and selectivity coefficients of 3-4 (against tramadol) and ~ 5 (against diphenhydramine). Therefore, we believe that the MIP-based ZNR sensing platform is promising for the practical detection of PHT and other drugs and evaluation of their proper dosages.

Background: Phenytoin (PHT) has been approved for the treatment of epilepsy. It belongs to the category of medications with a limited therapeutic window and requires therapeutic drug monitoring (TDM). PTH has been observed to induce a variety of Adverse drug reactions (ADRs) including ataxia, dystonia, nystagmus, dyskinesia, etc. Phenytoin-induced ataxia is an uncommonly observed ADR of Phenytoin whose reports are extremely limited. Case: Herein, we present a case report of a 16-year-old Asian patient with a past history of epilepsy that was admitted to a tertiary care hospital due to the development of ataxia, giddiness, and vomiting when taking Phenytoin in addition to Oxcarbazepine, Clobazam, and Levetiracetam to treat seizures. On admission, Magnetic resonance imaging (MRI) findings revealed bilateral variable cerebrospinal fluid (CSF) lesions in the parieto-occipital region of the periventricular area (periventricular leukomalacia). Additionally, serum Phenytoin levels were observed to be in the toxic range (40 μg/mL) due to which physicians confirmed the ADR to be due to Phenytoin toxicity. Thus, the Phenytoin drug was discontinued in the patient gradually and he was continued on clobazam, oxcarbazepine, and brivaracetam which led to reversal of the ADR in the patient. Conclusion: In this case, ataxia resulted from Phenytoin overdose, as confirmed by MRI and serum tests suggesting that TDM of Phenytoin is essential to prevent ADRs. Given the scarcity of ataxia cases caused by Phenytoin, awareness is lacking within the scientific community. Our aim is to provide insights to promote better monitoring and patient-centered treatment outcomes for epileptic patients.

Gingival enlargement is a side effect of several different medication, including immunosuppressants, anticonvulsants, and calcium channel blockers. It is an inflammatory response that starts when plaque and calculus build up on the tooth surface. The most prevalent long-term neurological condition affecting people is epilepsy. In affluent nations, the prevalence of epilepsy is ~ 1%, whereas in less developed countries, it may >2%. The preferred medication for the condition, phenytoin, has major side effects include gingival enlargement. In addition to being visually disfiguring, this enlargement frequently affects speech, chewing and eating. Furthermore, those with poor dental hygiene, causes disabilities with motor coordination and muscular limitations leading to mental disability and physical impairments are more prone to periodontal disease. This article enlightened the mechanism of drug induced gingival enlargement clinically, microbiologically, and surgically.

BACKGROUND: Severe acne breakouts often lead to atrophic acne scars, which affect millions of people worldwide and can significantly affect a person\'s self-confidence and self-image. Given the difficulty in treating atrophic acne scars, this study aims to investigate the efficacy of topical phenytoin in the treatment of atrophic acne scars.
METHODS: This split face clinical trial on 25 patients between the ages of 18 and 40 involved the application of microneedling on one side of the face, with three sessions taking place over the course of a month. On the other side, a 1% phenytoin cream was administered three times daily for 1 week following the microneedling procedure. Baseline information was collected for all patients, and follow-up assessments were conducted during the treatment sessions and 2 months after the last session. The assessments included evaluating the number and area of pores and spots, determining scar severity, assessing patient satisfaction, and recording any potential complications.
RESULTS: Among patients, 20 individuals (80%) were females, and the average age of the participants was 35.96 ± 9.23. In terms of the fine pore area, despite the fine pore count, both groups showed improvement over time (p: 0.03 vs. 0.06). Also, regarding large pore count and area, and the count and area of spots, both groups showed improvement over time (p: 0.001). However, there were no significant differences between the two groups (p > 0.05). On the other hand, when it comes to acne scar grade and patients\' satisfaction, the phenytoin group outperformed the control group in all follow-up sessions and this difference was found to be significant (p: 0.001). It is worth noting that no complications were observed among any of the patients.
CONCLUSIONS: It appears that combining phenytoin cream with microneedling has a more effective therapeutic outcome in enhancing atrophic acne scars, when compared to microneedling alone, and this method can be regarded as a viable alternative in treating these types of scars.

The sodium (Na+) leak channel (NALCN) is a member of the four-domain voltage-gated cation channel family that includes the prototypical voltage-gated sodium and calcium channels (NaVs and CaVs, respectively). Unlike NaVs and CaVs, which have four lateral fenestrations that serve as routes for lipophilic compounds to enter the central cavity to modulate channel function, NALCN has bulky residues (W311, L588, M1145, and Y1436) that block these openings. Structural data suggest that occluded fenestrations underlie the pharmacological resistance of NALCN, but functional evidence is lacking. To test this hypothesis, we unplugged the fenestrations of NALCN by substituting the four aforementioned residues with alanine (AAAA) and compared the effects of NaV, CaV, and NALCN blockers on both wild-type (WT) and AAAA channels. Most compounds behaved in a similar manner on both channels, but phenytoin and 2-aminoethoxydiphenyl borate (2-APB) elicited additional, distinct responses on AAAA channels. Further experiments using single alanine mutants revealed that phenytoin and 2-APB enter the inner cavity through distinct fenestrations, implying structural specificity to their modes of access. Using a combination of computational and functional approaches, we identified amino acid residues critical for 2-APB activity, supporting the existence of drug binding site(s) within the pore region. Intrigued by the activity of 2-APB and its analogues, we tested compounds containing the diphenylmethane/amine moiety on WT channels. We identified clinically used drugs that exhibited diverse activity, thus expanding the pharmacological toolbox for NALCN. While the low potencies of active compounds reiterate the pharmacological resistance of NALCN, our findings lay the foundation for rational drug design to develop NALCN modulators with refined properties.