Pharmacokinetics and pharmacodynamics of oral acetaminophen in combination with codeine in healthy Greyhound dogs

Pharmacokinetics and effects of codeine in combination with acetaminophen on thermal nociception in horses

Codeine and acetaminophen in combination have proven to be an effective analgesic treatment for moderate-to-severe and postoperative pain in humans. Studies have demonstrated that codeine and acetaminophen, when administered as sole agents, are well tolerated by horses. In the current study, we hypothesized that administration of the combination of codeine and acetaminophen would result in a significant thermal antinociceptive effect compared with administration of either alone. Six horses were administered oral doses of codeine (1.2 mg/kg), acetaminophen (20 mg/kg), and codeine plus acetaminophen (1.2 mg/kg codeine and 6-6.4 mg/kg acetaminophen) in a three-way balanced crossover design. Plasma samples were collected, concentrations of drug and metabolites determined via liquid chromatography-mass spectrometry, and pharmacokinetic analyses were performed. Pharmacodynamic outcomes, including effect on thermal thresholds, were assessed. Codeine Cmax and AUC were significantly different between the codeine and combination group. There was considerable inter-individual variation in the pharmacokinetic parameters for codeine, acetaminophen, and their metabolites in horses. All treatments were well tolerated with minimal significant adverse effects. An increase in the thermal threshold was noted at 1.5 and 2 h, from 15 min through 6 h and 0.5, 1, 1.5, and 3 h in the codeine, acetaminophen, and combination groups, respectively.

Multimodal Approach to Pain Management in Veterinary Rehabilitation

Pain recognition, assessment, and management is a primary focus and an integral part of veterinary rehabilitation. Evidence-based pain mitigation protocols will use both pharmacologic tools and nonpharmacologic methods to create a customized, safe, and effective treatment plan. A multimodal, patient-centered approach will allow for the best outcomes for pain relief and improved quality of life.

Prophylactic efficacy of intravenous paracetamol administration to reduce the incidence of post-operative ocular hypertension in dogs undergoing phacoemulsification: A pilot study

PURPOSE

To determine whether intravenous administration of paracetamol can prevent postoperative ocular hypertension (POH) in dogs following routine phacoemulsification.

METHODS

Diabetic and non-diabetic patients (total 54 dogs) undergoing unilateral or bilateral phacoemulsification were recruited to this placebo-controlled, prospective study. The control group received 1 ml/kg saline via intravenous infusion while the treatment group received 10 mg/kg paracetamol via intravenous infusion. Infusions were administered 30 min prior to surgery and repeated 12 h following initial administration. All patients received topical latanoprost at the conclusion of surgery. Intraocular pressure (IOP) was measured before premedication (baseline), and at 1 h, 3 h, 5 h and 18 h following extubation. POH was defined as an IOP above 25 mmHg (POH25). In addition, the number of patients with an IOP exceeding 20 mmHg was analyzed (POH20).

RESULTS

POH20 occurred in 33 of 54 animals (61.1%), including 19 of 25 animals (76.0%) in the control group and 14 of 29 animals (55.2%) in the treatment group. POH25 occurred in 23 of 44 animals (52.3%), including 13 of 25 animals (52.0%) in the control group and 10 of 29 animals (34.5%) in the treatment group. Paracetamol administration showed a significant positive effect on reducing the incidence of POH20 (p = .048), but not POH25 (p = .221).

CONCLUSIONS

When comparing groups, treatment with paracetamol showed a statistically significant reduction in the incidence of POH20, although no differences were observed in the incidence of POH25 between groups. Further studies are warranted to explore whether alternative drug regimes or routes of administration can provide enhanced efficacy in the prevention of POH25.

Influence of general anaesthesia on the intravenous acetaminophen pharmacokinetics in Beagle dogs

OBJECTIVE

To determine if general anaesthesia influences the intravenous (IV) pharmacokinetics (PK) of acetaminophen in dogs.

STUDY DESIGN

Prospective, crossover, randomized experimental study.

ANIMALS

A group of nine healthy Beagle dogs.

METHODS

Acetaminophen PK were determined in conscious and anaesthetized dogs on two separate occasions. Blood samples were collected before, and at 5, 10, 15, 30, 45, 60 and 90 minutes and 2, 3, 4, 6, 8, 12 and 24 hours after 20 mg kg^-1 IV acetaminophen administration. Haematocrit, total proteins, albumin, alanine aminotransferase, aspartate aminotransferase, urea and creatinine were determined at baseline and 24 hours after acetaminophen. The anaesthetized group underwent general anaesthesia (90 minutes) for dental cleaning. After the administration of dexmedetomidine (3 μg kg^-1) intramuscularly, anaesthesia was induced with propofol (2-3 mg kg^-1) IV, followed by acetaminophen administration. Anaesthesia was maintained with isoflurane in 50% oxygen (Fe'Iso 1.3-1.5%). Dogs were mechanically ventilated. Plasma concentrations were analysed with high-performance liquid chromatography. PK analysis was undertaken using compartmental modelling. A Wilcoxon test was used to compare PK data between groups, and clinical laboratory values between groups, and before versus 24 hours after acetaminophen administration. Data are presented as median and range (p < 0.05).

RESULTS

A two-compartmental model best described time-concentration profiles of acetaminophen. No significant differences were found for volume of distribution values 1.41 (0.94-3.65) and 1.72 (0.89-2.60) L kg^-1, clearance values 1.52 (0.71-2.30) and 1.60 (0.91-1.78) L kg^-1 hour^-1 or terminal elimination half-life values 2.45 (1.45-8.71) and 3.57 (1.96-6.35) hours between conscious and anaesthetized dogs, respectively. Clinical laboratory variables were within normal range. No adverse effects were recorded.

CONCLUSIONS AND CLINICAL RELEVANCE

IV acetaminophen PK in healthy Beagle dogs were unaffected by general anaesthesia under the study conditions. Further studies are necessary to evaluate the PK in different clinical contexts.

Extracorporeal Therapies in the Emergency Room and Intensive Care Unit

Extracorporeal treatments create opportunity for removing disease causing solutes within blood. Intoxications, renal failure, and immune-mediated diseases may be managed with these treatments, often providing new hope for patients with severe or refractory disease. Understanding solute pharmacokinetics and the limitations of each type of extracorporeal technique can allow for the selection of the optimal treatment modality.

Multiple-dose pharmacokinetics and opioid effects of a novel analgesic with a deterrent to human opioid abuse (methadone-fluconazole-naltrexone) after oral administration in dogs

OBJECTIVE

To assess the pharmacokinetics and opioid effects of methadone after administration of multiple doses by means of 2 dosing regimens of methadone-fluconazole-naltrexone.

ANIMALS

12 healthy Beagles.

PROCEDURES

Dogs were randomly allocated (6 dogs/group) to receive 1 of 2 oral dosing regimens of methadone-fluconazole-naltrexone. Treatment 1 doses were administered at 0 (methadone-to-fluconazole-to-naltrexone ratio of 1:5:0.25 mg/kg), 14 (1:5:0.25), 24 (0.5:2.5:0.125), and 38 (0.5:2.5:0.125) hours. Treatment 2 doses were administered at 0 (1:5:0.25), 4 (0.5:2.5:0.125), 10 (0.5:2.5:0.125), and 24 (0.5:2.5:0.125) hours. Blood samples, rectal temperatures, and von Frey antinociceptive measurements were obtained at designated times.

RESULTS

Compared with baseline, temperatures significantly decreased for treatment 1 group dogs at 2 to ≥ 4 hours and from 16 to ≥ 50 hours (12 hours after last dose) and for treatment 2 group dogs at 2 to ≥ 36 hours (12 hours after last dose), when trough methadone concentrations were ≥ 21.3 ng/mL. Antinociception occurred after the first dose but was not maintained throughout the study. Lesions were noted in some dogs at the application site of the von Frey device. Naltrexone and β-naltrexol were sporadically detected in plasma, and naltrexone glucuronide was consistently detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Opioid effects were noted after oral administration of the first dose, and data suggested that administering a second dose 6 hours later and every 12 hours thereafter was necessary to maintain opioid effects. Antinociception may have been lost because dogs became averse or hyperalgesic to the von Frey device, such that the antinociception model used here may not be robust for repeated measurements in dogs.

Comparison of the effects on lameness of orally administered acetaminophen-codeine and carprofen in dogs with experimentally induced synovitis

OBJECTIVE

To compare the ability of acetaminophen-codeine (AC; 15.5 to 18.5 mg/kg and 1.6 to 2.0 mg/kg, respectively) or carprofen (4.2 to 4.5 mg/kg) administered PO to attenuate experimentally induced lameness in dogs.

ANIMALS

7 purpose-bred dogs.

PROCEDURES

A blinded crossover study was performed. Dogs were randomly assigned to receive AC or carprofen treatment first and then the alternate treatment a minimum of 21 days later. Synovitis was induced in 1 stifle joint during each treatment by intra-articular injection of sodium urate (SU). Ground reaction forces were assessed, and clinical lameness was scored at baseline (before lameness induction) and 3, 6, 9, 12, 24, 36, and 48 hours after SU injection. Plasma concentrations of acetaminophen, carprofen, codeine, and morphine were measured at various points. Data were compared between and within treatments by repeated-measures ANOVA.

RESULTS

During AC treatment, dogs had significantly higher lameness scores than during carprofen treatment at 3, 6, and 9 hours after SU injection. Peak vertical force and vertical impulse during AC treatment were significantly lower than values during carprofen treatment at 3, 6, and 9 hours. Plasma concentrations of carprofen (R)- and (S)-enantiomers ranged from 2.5 to 19.2 μg/mL and 4.6 to 25.0 μg/mL, respectively, over a 24-hour period. Plasma acetaminophen concentrations ranged from 0.14 to 4.6 μg/mL and codeine concentrations from 7.0 to 26.8 ng/mL, whereas plasma morphine concentrations ranged from 4.0 to 58.6 ng/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen as administered was more effective than AC at attenuating SU-induced lameness in dogs.

Clinical evaluation of postoperative analgesia, cardiorespiratory parameters and changes in liver and renal function tests of paracetamol compared to meloxicam and carprofen in dogs undergoing ovariohysterectomy

Background

In veterinary medicine, the administration of nonsteroidal anti-inflammatory analgesics (NSAIDs) for the control of postsurgical pain in dogs and cats is common given the anti-inflammatory, analgesic, and antipyretic effects of these drugs. This study compared the serum biochemical changes and postoperative analgesic effects of paracetamol, meloxicam, and carprofen in bitches submitted to an ovariohysterectomy using the Dynamic Interactive Visual Analog Scale (DIVAS) and Pain Scale of the University of Melbourne (UMPS) scoring systems.

Methods

Thirty bitches of different breeds underwent elective ovariohysterectomies and were randomly assigned to one of three treatment groups: a paracetamol group [15 mg kg^-1 intravenous (IV)], a carprofen group (4 mg kg^-1 IV), and a meloxicam group (0.2 mg kg^-1 IV). All treatments were administered 30 minutes prior to surgery. Paracetamol was administered every 8 hours postoperatively for 48 hours total, while carprofen and meloxicam were intravenously administered every 24 hours. An evaluation of post-surgical pain was done with the DIVAS and the UMPS. The first post-surgical pain measurement was performed 1 hour after surgery and then 2, 4, 6, 8, 12, 16, 20, 24, 36, and 48 hours after surgery.

Results

All groups exhibited a gradual reduction in pain throughout the postoperative period in both scales; however, neither scale significantly differed between the three treatment groups (P > 0.05) during the 48 postoperative hours.

Conclusions

Paracetamol was as effective as meloxicam and carprofen for post-surgical analgesia in bitches subjected to elective ovariohysterectomy. The present study demonstrates that paracetamol may be considered a tool for the effective treatment of acute perioperative pain in dogs. Furthermore, this drug led to no adverse reactions or changes in the parameters assessed in the present study, indicating its safety.

Antiinflammatory Drugs

This article reviews the mechanisms of action, clinical use, and recent scientific evidence for the use of nonsteroidal antiinflammatory drugs, grapiprant, acetaminophen (paracetamol), metamizole (dipyrone), and corticosteroids in pain management. The discussion is presented with an emphasis on the treatment of acute pain.

Conservative Management of Hip Dysplasia

Hip dysplasia (HD) is a common orthopedic condition seen in small animal patients that leads to osteoarthritis of the coxofemoral joint. The disease can be managed conservatively or surgically. The goals of surgical treatment in the immature patient are to either prevent the clinical signs of HD or to prevent or slow the progression of osteoarthritis. In mature patients surgery is used as a salvage procedure to treat debilitating osteoarthritis. Conservative management can be used in dogs with mild or intermittent clinical signs and includes nutritional management and weight control, exercise modification, physical rehabilitation, pain management and disease-modifying agents.

Rapid absorption of diclofenac and acetaminophen after their oral administration to cattle

The oral pharmacokinetics of diclofenac (DF) were evaluated in cattle by analyzing plasma concentration-time data after its intravenous and oral administration in order to propose the oral administration of DF as effective route to avoid long withdraw period. DF was intravenously and orally administered at 1 mg/kg to cattle using a crossover design with a 4-week washout period. Plasma concentrations of DF were determined by a HPLC analysis. The mean absorption time (MAT) and absorption half-life (t_1/2ka) were 1.61 ± 0.61 and 1.51 ± 0.38 hr, respectively, and bioavailability was nearly 100%. The oral pharmacokinetics of acetaminophen (AAP) were also evaluated in cattle. Plasma concentrations of AAP were determined by a HPLC analysis. MAT and t_1/2ka were 2.85 ± 0.93 and 1.53 ± 0.28 hr, respectively, and bioavailability was approximately 70%. In conclusion, the results of the present study indicate that DF and AAP are rapidly absorbed from the forestomach of cattle. Therefore, the appropriate efficacies of these drugs may be achieved via their oral administration, even in cattle.