Investigation of the Combination of Pregabalin with Duloxetine or Amitriptyline on the Pharmacokinetics and Antiallodynic Effect During Neuropathic Pain in Rats.

BACKGROUND: Amitriptyline, duloxetine, and pregabalin are among the most pharmacotherapeutic, effective treatments for neuropathic pain control. However, the evaluation of synergism by combining these treatments is still poorly investigated. OBJECTIVES: To evaluate the pharmacokinetics of the combination of pregabalin plus duloxetine and pregabalin plus amitriptyline, as well as the effect of these on neuropathic pain on rodent model. STUDY DESIGN: The experimental study. SETTING: The research took place in the research laboratories at the Federal University of Alfenas after ethics committee approval. METHODS: This study used male Wistar rats weighing between 220 and 250 g. The animals were randomly divided into the following groups: monotherapy (pregabalin, amitriptyline, duloxetine), combined therapy (pregabalin + amitriptyline, pregabalin + duloxetine), and vehicle (ultrapure water). Pharmacokinetic analysis of pregabalin or combination (pregabalin + amitriptyline or pregabalin + duloxetine) in the plasma were performed by ultraperformance liquid chromatography tandem mass spectrometry. Neuropathic pain was induced by sciatic nerve constriction (chronic constriction injury [CCI]) model, and nociceptive threshold was measured by von Frey filaments test. In addition, to evaluate the influence of the treatments on the motor coordination, the rotarod test was used. RESULTS: The pharmacokinetic disposition of pregabalin was changed in the association with amitriptyline, presenting a clearance reduction and consequently an increase in bioavailability. Furthermore, after the 14th day of CCI, pregabalin was administered orally and induced antiallodynic effect after 1, 2:15, 4, and 8 hours of its administration and showed the greatest antiallodynic effect after 4 hours of its administration. Moreover, this effect was prolonged (up to 8 hours) by combination with amitriptyline. Additionally, pregabalin and pregabalin + duloxetine showed a hypoalgesic effect in sham rats. In addition, the rotarod test results showed that drugs did not influence the motor coordination of the rats. LIMITATIONS: Potential competition mechanisms during the excretion of pregabalin, when pregabalin was combined with amitriptyline, were not investigated in this study. CONCLUSIONS: The data demonstrated that combined therapy of pregabalin plus amitriptyline improved the bioavailability of pregabalin and potentiated the efficacy of the antiallodynic effect of pregabalin alone, proving to be advantageous for the treatment of sciatic neuropathic pain.

Influence of N-hexane inhalation on the enantioselective pharmacokinetics and metabolism of verapamil in rats.

Verapamil (VER) is commercialized as a racemic mixture of the (+)-(R)-VER and (-)-(S)-VER enantiomers. VER is biotransformed into norverapamil (NOR) and other metabolites through CYP-dependent pathways. N-hexane is a solvent that can alter the metabolism of CYP-dependent drugs. The present study investigated the influence of n-hexane (nose-only inhalation exposure chamber at concentrations of 88, 176, and 352 mg/m3) on the kinetic disposition of the (+)-(R)-VER, (-)-(S)-VER, (R)-NOR and (S)-NOR in rats treated with a single dose of racemic VER (10 mg/kg). VER and NOR enantiomers in rat plasma was analyzed by LC-MS/MS (m/z = 441.3 > 165.5 for the NOR and m/z 455.3 > 165.5 for the VER enantiomers) using a Chiralpak AD column. Pharmacokinetic analysis was performed using a monocompartmental model. The pharmacokinetics of VER was enantioselective in control rats, with higher plasma proportions of the (-)-(S)-VER eutomer (AUC(0-infinity) = 250.8 vs. 120.4 ng/ml/h; P < or = 0.05, Wilcoxon test). The (S)-NOR metabolite was also found to accumulate in plasma of control animals, with an S/R AUC(0-infinity) ratio of 1.5. The pharmacokinetic parameters AUC(0-infinity), Cl/F, Vd/F, and t(1/2) obtained for VER and NOR enantiomers were not altered by nose-only exposure to n-hexane at concentrations of 88, 176, or 352 mg/m3 (P > 0.05, Kruskal-Wallis test). However, the verapamil kinetic disposition was not enantioselective for the animals exposed to n-hexane at concentrations equal to or higher than the TLV-TWA. This finding is relevant considering that the (-)-(S)-VER eutomer is 10-20 times more potent than R-(+)-VER in terms of its chronotropic effect on atrioventricular conduction in rats and humans.

COVID-19 Pandemic - A Narrative Review of the Potential Roles of Chloroquine and Hydroxychloroquine.

BACKGROUND: Chloroquine (CQ) and hydroxychloroquine (HCQ) are old drugs used against malaria, rheumatism, inflammation in the joints, lupus, among others. These drugs showed positive results in preliminary scientific research for treatment of the severe acute respiratory syndrome coronavirus (SARS-CoV-2). Since the studies with CQ and HCQ are initial with small patient populations, it is not yet known whether there are adverse effects from the use of CQ and HCQ for patients infected with the coronavirus. OBJECTIVES: The aim of this study was to evaluate the evidence regarding the efficacy and safety of CQ and HCQ used against viral infection caused by SARS-CoV-2. STUDY DESIGN: This is a narrative review of the traditional prescriptions of CQ and HCQ efficacy and adverse effects as well as their employment for coronavirus disease 2019 (COVID-19). SETTING: In vitro and clinical studies comparing the antiviral efficacy and adverse effect profile of CQ and HCQ against COVID-19 in adult patients were evaluated. METHODS: A systemic search of reviews, including in vitro and clinical trial studies in English focusing on CQ and HCQ effects and adverse effects against COVID-19 in the adult patient population from PubMed was performed. It included studies reporting chloroquine and hydroxychloroquine effects and adverse effects against COVID-19. RESULTS: A total of 42 articles published between 2004 and April 2020 were reviewed for therapeutic use of CQ and HCQ. Both these drugs showed a significant in vitro potential against coronavirus. Many studies for clinical use of CQ and HCQ showed that patients presented adverse reactions on high doses. LIMITATIONS: Clinical studies have some methodology shortcomings, such as lack of information about the treatment and small number of experimental patients, leading to a misinterpretation of the data. Besides, there are few clinical studies with a limited sample size. Moreover, most of them did not present control groups, and some patients had died during these protocols. DISCUSSION: Despite both CQ and HCQ in vitro antiviral evidence, clinically, both drugs, either alone or combined with other medications, may increase the risk of cardiac arrhythmias, leading to cardiac arrest and sudden death. Besides, a lot of uncertainty still remains, such as starting administration period, dose prescribed, length of treatment, patients' condition, concomitant drug use, among others. CONCLUSION: From the studies reviewed, it is not possible to state the precise efficacy and safety of CQ and HCQ use in the treatment of COVID-19 at any time in the course of the disease. Future studies are warranted.

Identification and proportion of the enantiomers of the antihypertensive drug chlortalidone in its Form II by high quality single-crystal X-ray diffraction data.

Chlortalidone (CTD) is a diuretic drug largely used as part of antihypertensive therapies. It is marketed as an equimolar mixture of its enantiomers in the racemic crystal phase named Form I, despite of the higher aqueous solubility of another crystal form. The latter, named Form II, was thought to contain both enantiomers as a racemic conglomerate, i.e., in the form of a mixture of crystals, half of which consists solely of the (R)-enantiomer, the other half the (S)-enantiomer. The occurrence of both enantiomers in individual crystals of CTD Form II was demonstrated in this study. Spontaneous resolution does really occur upon crystallization, as presumed previously even without physical evidence of the (S)-enantiomer. Both (R) and (S)-enantiomers were successfully identified as two domains of a twinned by inversion single crystal of CTD Form II. A reliable Flack parameter of 0.14(4) allowed to determine the proportion of the enantiomers in the crystal, which is formed with 86% of the (R)-enantiomer and 14% of the (S)-enantiomer.