The retinoprotective role of phenytoin

Chemical Behavior and Bioactive Properties of Spinorphin Conjugated to 5,5'-Dimethyl- and 5,5'-Diphenylhydantoin Analogs

The discovery of new peptides and their derivatives is an outcome of ongoing efforts to identify a peptide with significant biological activity for effective usage as a possible therapeutic agent. Spinorphin peptides have been documented to exhibit numerous applications and features. In this study, biologically active peptide derivatives based on novel peptide analogues of spinorphin conjugated with 5,5'-dimethyl (Dm) and 5,5'-diphenyl (Ph) hydantoin derivatives have been successfully synthesized and characterized. Scanning electron microscopy (SEM) and spectral methods such as UV-Vis, FT-IR (Fourier Transform Infrared Spectroscopy), CD (Circular Dichroism), and fluorimetry were used to characterize the microstructure of the resulting compounds. The results revealed changes in peptide morphology as a result of the restructuring of the aminoacidic sequences and aromatic bonds, which is related to the formation of intermolecular hydrogen bonds between tyrosyl groups and the hydantoin moiety. Electrochemical and fluorescence approaches were used to determine some physicochemical parameters related to the biological behavior of the compounds. The biological properties of the spinorphin derivatives were evaluated in vivo for anticonvulsant activity against the psychomotor seizures at different doses of the studied peptides. Both spinorphin analog peptides with Ph and Dm groups showed activity against all three phases of the seizure in the intravenous Pentylenetetrazole Seizure (ivPTZ) test. This suggests that hydantoin residues do not play a crucial role in the structure of spinorphin compounds and in determining the potency to raise the seizure threshold. On the other hand, analogs with a phenytoin residue are active against the drug-resistant epilepsy test (6-Hz test). In addition, bioactivity analyses revealed that the new peptide analogues have the potential to be used as antimicrobial and antioxidant compounds. These findings suggest promising avenues for further research that may lead to the development of alternative medicines or applications in various fields beyond epilepsy treatment.

Perimetry Criteria For Assessing The Effectiveness Of Retinoprotective Therapy

Objective — To evaluate the effect of the frequency of retinoprotective therapy courses on perimetry parameters, to compare Octopus 900 perimeter with Octopus 600 perimeter, and to assess threshold perimetry results of G-dynamic versus 24-2 programs. Material and Methods — The study involved 17 patients (34 eyes) diagnosed with primary open-angle glaucoma of advanced stage. Group 1 included subjects receiving a course of Retinalamin every 3 months. Group 2 comprised patients undergoing Retinalamin therapeutics every 6 months. Results — At the onset of the study via G-dynamic and 24-2 programs, we did not observe any statistically significant differences between the groups in mean deviation of retinal photosensitivity (MD) and pattern standard deviation of mean retinal photosensitivity (PSD). However, the absolute values differed between groups and between programs. On average, the differences in MD and PSD values obtained in the photosensitivity study with G-dynamic vs. 24-2 programs were -0.36 dB (CI 95%: -4.27; 3.54) and 0.63 dB (CI 95%: 2.37; -1.11), respectively. Hence, studies performed via 24-2 and G-dynamic programs yielded comparable results (no statistically significant differences). However, they could not be identical due to different spatial arrangement of points in different programs. Conclusion — As a result of conducted treatment, retinal photosensitivity did not exhibit statistically significant changes; however, we observed positive dynamics in both groups in MD and PSD parameters of mean retinal photosensitivity. Different devices (Octopus 600 and Octopus 900 perimeters) and different programs (24-2, G-dynamic) yielded different outcomes due to their technical features and capabilities of reproducibility; however, these differences were not statistically significant.

Screening for Activity Against AMPA Receptors Among Anticonvulsants-Focus on Phenytoin

The interest in AMPA receptors as a target for epilepsy treatment increased substantially after the approval of perampanel, a negative AMPA receptor allosteric antagonist, for the treatment of partial-onset seizures and generalized tonic-clonic seizures. Here we performed a screening for activity against native calcium-permeable AMPA receptors (CP-AMPARs) and calcium-impermeable AMPA receptors (CI-AMPARs) among different anticonvulsants using the whole-cell patch-clamp method on isolated Wistar rat brain neurons. Lamotrigine, topiramate, levetiracetam, felbamate, carbamazepine, tiagabin, vigabatrin, zonisamide, and gabapentin in 100-µM concentration were practically inactive against both major subtypes of AMPARs, while phenytoin reversibly inhibited them with IC50 of 30 ± 4 μM and 250 ± 60 µM for CI-AMPARs and CP-AMPARs, respectively. The action of phenytoin on CI-AMPARs was attenuated in experiments with high agonist concentrations, in the presence of cyclothiazide and at pH 9.0. Features of phenytoin action matched those of the CI-AMPARs pore blocker pentobarbital, being different from classical competitive inhibitors, negative allosteric inhibitors, and CP-AMPARs selective channel blockers. Close 3D similarity between phenytoin and pentobarbital also suggests a common binding site in the pore and mechanism of inhibition. The main target for phenytoin in the brain, which is believed to underlie its anticonvulsant properties, are voltage-gated sodium channels. Here we have shown for the first time that phenytoin inhibits CI-AMPARs with similar potency. Thus, AMPAR inhibition by phenytoin may contribute to its anticonvulsant properties as well as its side effects.

A review of possible therapies for multiple sclerosis

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system with a wide range of symptoms, like executive function defect, cognitive dysfunction, blurred vision, decreased sensation, spasticity, fatigue, and other symptoms. This neurological disease is characterized by the destruction of the blood-brain barrier, loss of myelin, and damage to neurons. It is the result of immune cells crossing the blood-brain barrier into the central nervous system and attacking self-antigens. Heretofore, many treatments proved that they can retard the progression of the disease even though there is no cure. Therefore, treatments aimed at improving patients' quality of life and reducing adverse drug reactions and costs are essential. In this review, the treatment approaches to alleviate the progress of MS include the following: pharmacotherapy, antibody therapy, cell therapy, gene therapy, and surgery. The current treatment methods of MS are described in terms of the prevention of myelin shedding, the promotion of myelin regeneration, and the protection of neurons.

Screening Medications for Association with Progression to Wet Age-Related Macular Degeneration

PURPOSE

There is an urgent need for treatments that prevent or delay development to advanced age-related macular degeneration (AMD). Drugs already on the market for other conditions could affect progression to neovascular AMD (nAMD). If identified, these drugs could provide insights for drug development targets. The objective of this study was to use a novel data mining method that can simultaneously evaluate thousands of correlated hypotheses, while adjusting for multiple testing, to screen for associations between drugs and delayed progression to nAMD.

DESIGN

We applied a nested case-control study to administrative insurance claims data to identify cases with nAMD and risk-set sampled controls that were 1:4 variable ratio matched on age, gender, and recent healthcare use.

PARTICIPANTS

The study population included cases with nAMD and risk set matched controls.

METHODS

We used a tree-based scanning method to evaluate associations between hierarchical classifications of drugs that patients were exposed to within 6 months, 7 to 24 months, or ever before their index date. The index date was the date of first nAMD diagnosis in cases. Risk-set sampled controls were assigned the same index date as the case to which they were matched. The study was implemented using Medicare data from New Jersey and Pennsylvania, and national data from IBM MarketScan Research Database. We set an a priori threshold for statistical alerting at P ≤ 0.01 and focused on associations with large magnitude (relative risks ≥ 2.0).

MAIN OUTCOME MEASURES

Progression to nAMD.

RESULTS

Of approximately 4000 generic drugs and drug classes evaluated, the method detected 19 distinct drug exposures with statistically significant, large relative risks indicating that cases were less frequently exposed than controls. These included (1) drugs with prior evidence for a causal relationship (e.g., megestrol); (2) drugs without prior evidence for a causal relationship, but potentially worth further exploration (e.g., donepezil, epoetin alfa); (3) drugs with alternative biologic explanations for the association (e.g., sevelamer); and (4) drugs that may have resulted in statistical alerts due to their correlation with drugs that alerted for other reasons.

CONCLUSIONS

This exploratory drug-screening study identified several potential targets for follow-up studies to further evaluate and determine if they may prevent or delay progression to advanced AMD.

Identification of significant protein markers by mass spectrometry after co-treatment of cells with different drugs: An in vitro survey platform

RATIONALE

Understanding drug-drug interactions and predicting the side effects induced by polypharmacy are difficult because there are few suitable platforms that can predict drug-drug interactions and possible side effects. Hence, developing a platform to identify significant protein markers of drug-drug interactions and their associated side effects is necessary to avoid adverse effects.

METHODS

Human liver cells were treated with ethosuximide in combination with cimetidine, ketotifen, metformin, metronidazole, or phenytoin. After sample preparation and extraction, mitochondrial proteins from liver cells were isolated and digested with trypsin. Then, peptide solutions were detected using a nano ultra-performance liquid chromatographic system combined with tandem mass spectrometry. The Ingenuity Pathway Analysis tool was used to simulate drug-drug interactions and identify protein markers associated with drug-induced adverse effects.

RESULTS

Several protein markers were identified by the proposed method after liver cells were co-treated with ethosuximide and other drugs. Several of these protein markers have previously been reported in the literature, indicating that the proposed platform is workable.

CONCLUSIONS

Using the proposed in vitro platform, significant protein markers of drug-drug interactions could be identified by mass spectrometry. This workflow can then help predict indicators of drug-drug interactions and associated adverse effects for increased safety in clinical prescriptions.

Effect of phenytoin on retinal ganglion cells in acute isolated optic neuritis

OBJECTIVE

Phenytoin has been shown to reduce the peripapillary retinal nerve fiber layer (pRNFL) loss in optic neuritis (ON). We evaluated the effects of phenytoin on retinal ganglion layers and visual outcomes of newly diagnosed acute ON.

METHODS

A randomized, placebo-controlled trial was conducted in a tertiary referral eye hospital and patients with the first episode of typical demyelinating ON, without any history of multiple sclerosis were randomly assigned to phenytoin or placebo. The thickness of ganglion cell-inner plexiform layer (GCIPL) measured by optical coherence tomography (OCT) was considered as the primary outcome.

RESULTS

One patient in the phenytoin group developed severe cutaneous rashes that progressed to Stevens-Johnson syndrome (SJS)/toxic epidermal necrosis (TEN), and further allocation of patients to the phenytoin group was stopped, and finally fifteen participants were included in the phenytoin group. Fifty-one patients were enrolled to the placebo group, from which four were excluded. Both visual acuity and field were not significantly different between the control and phenytoin groups after 1 and 6 months. Mean 3- and 6-mm macular GCIPL thicknesses decreased after 6 months to 73.6 ± 14.1 and 57.9 ± 7.5 μm, respectively, in the phenytoin group and to 71.6 ± 15.7 and 55.6 ± 6.6 μm, respectively, in the placebo group with no significant differences between the two groups (P = 0.77 and P = 0.26, respectively, linear multilevel model).

CONCLUSION

Phenytoin is not probably safe and effective as neuroprotection after acute ON. Further investigation with other sodium channel inhibitors could be considered.

Nanoemulsions and thermosensitive nanoemulgels of phenytoin and fosphenytoin for intranasal administration: Formulation development and in vitro characterization

Phenytoin is a low solubility anticonvulsant drug. It has, nonetheless, other possible therapeutic indications, such as neuropathic pain, including trigeminal neuralgia, or wound healing. Its use has decreased due to side effects, but nasal/intranasal administration could significantly increase drug safety and efficacy. The aim of this work was to develop and study nanoemulsions and thermosensitive nanoemulgels of phenytoin and fosphenytoin, in combination, for intranasal administration, with immediate and sustained release profiles. Nanoemulsions were prepared by adding the aqueous phase, containing gelling polymers in the case of nanoemulgels, to emulsion preconcentrates, followed, in the optimized procedure, by premix membrane emulsification. Formulation design and optimization was guided by drug strength, rheological behavior, osmolality, mean droplet size and polydispersity. Fosphenytoin interfered significantly with Carbopol but not with Pluronic's gelation, and allowed to achieve drug strengths equivalent to 22 or 27 mg/g of phenytoin in lead nanoemulsions, and 16.7 mg/g of phenytoin in the lead nanoemulgel. The final selected low viscosity nanoemulsions had an immediate or prolonged fosphenytoin release profile, depending of anhydrous phase proportion (10% or 40%, respectively). The thermosensitive nanoemulgel, with 10% anhydrous phase, showed prolonged drug release. Future studies will establish whether they are more suited for topical effects or therapeutic brain delivery.