Polymorphism and Pharmacological Assessment of Carbamazepine

Abstract

This work provides insight into carbamazepine polymorphs (Forms I, II, III, IV, and V), with reports on the cytoprotective, exploratory, motor, CNS-depressant, and anticonvulsant properties of carbamazepine (CBZ), carbamazepine formulation (CBZ-F), topiramate (TOP), oxcarbazepine (OXC), and diazepam (DZP) in mice. Structural analysis highlighted the significant difference in molecular conformations, which directly influence the physicochemical properties; and density functional theory description provided indications about CBZ reactivity and stability. In addition to neuron viability assessment in vitro, animals were treated orally with vehicle 10 mL/kg, as well as CBZ, CBZ-F, TOP, OXC, and DZP at the dose of 5 mg/kg and exposed to open-field, rotarod, barbiturate sleep induction and pentylenetetrazol (PTZ 70 mg/kg)-induced seizure. The involvement of GABAergic mechanisms in the activity of these drugs was evaluated with the intraperitoneal pretreatment of flumazenil (2 mg/kg). The CBZ, CBZ-F, and TOP mildly preserved neuronal viability. The CBZ-F and the reference AEDs potentiated barbiturate sleep, altered motor activities, and attenuated PTZ-induced convulsion. However, flumazenil pretreatment blocked these effects. Additional preclinical assessments could further establish the promising utility of CBZ-F in clinical settings while expanding the scope of AED formulations and designs.

Keywords: animal models; anticonvulsant; carbamazepine; cytoprotection; formulation; polymorphism.

Figure 1

Main interactions of the supramolecular arrangement of the carbamazepine forms. I (a), II (b), III (c), IV (d), and V (e).

Figure 2

Molecular packing in the unit cell for carbamazepine forms. I (a), II (b), III (c), IV (d), and V (e).

Figure 3

FMO representations for CBZ forms. I (a), II (b), III (c), IV (d), and V (e).

Figure 4

MEP map for CBZ forms. I (a), II (b), III (c), IV (d), and V (e).

Figure 5

Glutamate- and glycine-induced over-stimulation and excitotoxicity protocol for viability assessment in vitro. Cultured cortical neurons at 37 °C were treated with 10 µM of glutamate/1 µM of glycine for 1 h in the presence of VEH (vehicle), CBZ (carbamazepine), CBZ-F (carbamazepine formulation), TOP (topiramate), OXC (oxcarbazepine), and DZP (diazepam) at 1 mg/mL. The group of untreated cultured neuron without excitotoxic stimulation (sham) was assigned with 100% viability. Data are represented as mean ± SEM, n = 10 different cultures. * p < 0.05 and *** p < 0.001 as compared to the VEH; ### p < 0.001 as compared with the sham group (one-way ANOVA followed by Bonferroni’s post hoc test).

Figure 6

Effect of CBZ-F on the exploratory and motor activities in the open field and rotarod tests, respectively. Oral treatments with VEH (vehicle), CBZ (carbamazepine), CBZ-F (carbamazepine formulation), TOP (topiramate), OXC (oxcarbazepine) and DZP (diazepam), all at the dose of 5 mg/kg, were carried out. The parameters evaluated were total number of crossings (A) and number of rearings (B) in the open field as well as the fall latency (C) and the number of falls (D) in the rotarods. Each column represents mean ± S.E.M. (n = 10). One-way ANOVA and Dunnett’s post hoc test for multiple comparisons were performed. * p < 0.05, ** p < 0.01, and *** p < 0.001 for other treatment groups vs. vehicle-treated group.

Figure 7

Potentiation and blockade of barbiturate sleep induction. Effect of orally administered vehicle (10 mL/kg), CBZ, CBZ-F, DZP, TOP, and OXC (all 5 mg/kg) on (A) sleep latency and (B) sleep duration of sodium pentobarbital (40 mg/kg)-induced hypno-sedative effect. * Indicates p < 0.05, ** indicates p < 0.01 and *** indicates p < 0.001 as compared with vehicle-treated group (one-way ANOVA followed by Dunnett’s post hoc test). All groups were treated with sodium pentobarbital (40 mg/kg, i.p.). Results are expressed as mean ± SEM; n = 10 in each group. VEH (vehicle), CBZ (carbamazepine), CBZ-F (carbamazepine formulation), TOP (topiramate), OXC (oxcarbazepine), DZP (diazepam), and FLU (flumazenil).

Figure 8

Screening for anticonvulsant activity and its pharmacological blockade using pentylenetetrazol-induced seizure test. The effects of the vehicle (10 mL/kg), CBZ, CBZ-F, TOP, OXC, or DZP at 5 mg/kg on the latency (A), duration (B), and severity (C) of seizure were analyzed by either ANOVA and Dunnettʼs post hoc test with results in mean ± S.E.M. (n = 10). Statistical analysis was performed by one-way ANOVA followed by Dunnett’s post hoc test. * p < 0.05, ** p < 0.01, and *** p < 0.001 for other treatment groups vs. VEH group regarding the antiseizure-like effect of CBZ, CBZ-F, TOP, OXC, or DZP. VEH (saline), CBZ (carbamazepine), CBZ-F (carbamazepine formulation), TOP (topiramate), OXC (oxcarbazepine), DZP (diazepam) and FLU (flumazenil).