Pharmacokinetic analysis of two different doses of duloxetine following oral administration in dogs

Pharmacokinetic Study of a Soft Gelatin Capsule and a Solid-Supersaturatable SMEDDS Tablet of Dutasteride in Beagle Dogs

BACKGROUND AND OBJECTIVE

Dutasteride, an analog of testosterone, a 5α-reductase inhibitor is widely used in the treatment of moderate to severe symptomatic benign prostatic hyperplasia. The aim of this study was to compare the pharmacokinetic characteristics of dutasteride in beagle dogs after oral administration of a conventional soft gelatin capsule (Avodart^®) and a novel solid-supersaturatable soft-microemulsifying drug delivery system (SMEDDS) tablet.

METHODS

In this comparative dissolution study, the dissolution of dutasteride was pH-independent for both formulations. Noncompartmental analysis and modeling approaches were carried out to determine the pharmacokinetic parameters of dutasteride.

RESULTS

Approximately 90% of the drug dissolved in all media within 15 min, indicating that there was little difference in the dissolution rate of the solid-supersaturatable SMEDDS tablets and that of the commercial soft gelatin capsules. Using t test analysis, no statistically significant difference was detected in the pharmacokinetic parameters of the two formulations. The test/reference geometric mean ratios were 1.087 (90% confidence intervals 0.8529-1.3854) for the area under the plasma concentration versus time curve from 0 to the last time point (48 h) with a measurable concentration and 1.094 (90% confidence intervals 0.8909-1.3454) for maximum plasma concentration. Unfortunately, the bioequivalent criterium (0.8-1.25) was not met due to the small sample size, but the results of this study suggest a possible bioequivalence of dutasteride in the two formulations.

CONCLUSION

Based on the results of this study, the development of a tablet dosage form of dutasteride using a solid-supersaturatable SMEDDS should be considered for humans.

Duloxetine ingestion in 364 dogs

OBJECTIVE

To describe abnormal clinical signs following duloxetine ingestion in dogs.

ANIMALS

364 client-owned dogs that ingested duloxetine.

PROCEDURES

The American Society for the Prevention of Cruelty to Animals, Animal Poison Control Center electronic database was searched for records of dogs with duloxetine ingestion between January 2012 and December 2016. Data collected included age, body weight, breed, duloxetine exposure and dose, clinical signs, and overall outcome. Clinical signs were categorized as either neurologic, digestive, cardiovascular, respiratory, or metabolic and endocrine. Outcomes were categorized as no clinical signs, fully recovered, died, or unknown.

RESULTS

Clinical signs developed in 55 of the 364 (15.1%) dogs with known ingestion of duloxetine. The most common clinical signs were lethargy (22/55 [40%]), mydriasis (18/55 [33%]), vomiting (11/55 [20%]), and trembling (6/55 [11%]). Dogs that ingested an estimated dose of duloxetine ≥ 20 mg/kg (9.1 mg/lb) were more likely to have had abnormal clinical signs than were dogs that ingested < 20 mg/kg.

CONCLUSIONS AND CLINICAL RELEVANCE

Findings indicated that most dogs in the present study did not have clinical signs associated with ingestion of duloxetine and that development of clinical signs varied by individual dog. Further information is needed to determine toxic dose ranges for duloxetine ingestion in dogs. (J Am Vet Med Assoc 2019;255:1161-1166).

Validated Microemulsion Liquid Chromatography-Fluorescence Method for the Quantification of Duloxetine and its Two Main Metabolites in Plasma: Application to Clinical Pharmacokinetic Studies

Background:

Duloxetine (DL) is a selective serotonin and norepinephrine reuptake inhibitor. The drug is used in the treatment of major depression, anxiety, pain related to diabetic peripheral neuropathy and stress urinary incontinence. </P><P> Objective: This study described, for the first time, the development and validation of a highly selective and sensitive microemulsion liquid chromatography-fluorescence (MELC-FL) method with low environmental pollution and without extraction steps for the simultaneous quantification of DL, and its two main metabolites; 5-hydroxy-6-methoxy duloxetine (5-HDL) and 4-hydroxy duloxetine glucuronide (4- HDLG) in plasma.

Methods:

The studied analytes and methyl paraben (an internal standard) were detected using excitation and emission wavelengths of 280 and 340 nm, respectively. The analysis was performed on Water Symmetry C18 analytical column (100 Å, 150 mm x 3.9 mm, 5 µm) by directly injecting the plasma after appropriate dilution with microemulsion mobile phase. Total analytical run time was 4 min.

Results:

The MELC-FL method was statistically validated according to the FDA guidelines for bioanalytical methods for linearity, accuracy, precision, specificity, robustness, and stability. Linear calibration plots were achieved in the ranges of 25-1200 ng/mL for DL and 50-1500 ng/mL for 5-HDL and 4- HDLG (r2 ≥ 0.997) in rat plasma. The intra- and inter- assay precisions and accuracy were acceptable. The overall recoveries of DL and its two main metabolites from rat plasma were between 97.12% and 103.12% with an RSD value between 0.34% and 4.57%.

Conclusion:

The present study supports the possible use of the microemulsion mobile phase in LC as a “greener ” mobile phase. The developed method offered an advantage in the form of direct analysis of biological samples after appropriate dilution with eco-friendly microemulsion mobile phase, which decreased the possibility of sample loss during analysis. The developed assay was successfully applied in a pharmacokinetic study and it established the applicability of the method for the determination of concentration-time profiles of DL and its two main metabolites in rat plasma after systemic administration.

Enhanced Bioavailability of Tadalafil after Intranasal Administration in Beagle Dogs

Tadalafil is an oral selective phosphodiesterase type-5 inhibitor with demonstrated efficacy and safety that is used to treat erectile dysfunction. The purpose of this study is to compare the pharmacokinetic properties of tadalafil after conventional oral tablet administration and novel intranasal administration in beagle dogs. Fourteen 13-month-old male beagle dogs were randomly divided into two groups, and were given 5 mg tadalafil orally or intranasally in a parallel design. Blood samples were collected before and 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, and 36 h after administration. The plasma concentration of tadalafil was determined via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The systemic exposure and absorption rate of tadalafil were significantly greater in the intranasal administration group than in the oral administration group. A one-compartment model with first-order absorption and elimination was sufficient to explain the pharmacokinetic characteristics observed after both oral and intranasal administration. This study indicates that the development of tadalafil nasal delivery systems is feasible and may lead to better results than the conventional oral route.

Analgesia in the Perioperative Period

Untreated or undermanaged perioperative pain has systemic effects that may negatively impact a patient's welfare and return to function. A consistent analgesic plan that assesses a patient's pain and comfort at regular intervals during the perioperative period should be incorporated into practice. Validated pain assessment tools are available for use in dogs and cats. Multimodal analgesic plans should be created for individual patients and modified according to pain assessments. These plans, based on a thorough history, physical examination, and knowledge of the expected pain, should be combinations of an opioid, a nonsteroidal anti-inflammatory drug, a local anesthetic, and nonpharmacologic analgesic techniques.