Pharmacokinetics of tramadol in horses after intravenous, intramuscular and oral administration

Comprehensive overview of analytical and bioanalytical methodologies for the opioid analgesics - Tramadol and combinations

Synthetic opioids like Tramadol are used to treat mild to moderate pain. Its ability to relieve pain is about a tenth that of morphine. Furthermore, Tramadol shares similar effects on serotonin and norepinephrine to several antidepressants known as serotonin-norepinephrine reuptake inhibitors (SNRIs), such as venlafaxine and duloxetine. The present review paper discusses the recent developments in analytical methods for identifying drugs in pharmaceutical preparations and toxicological materials, such as blood, saliva, urine, and hair. In recent years, a wide variety of analytical instruments, including capillary electrophoresis, NMR, UV-visible spectroscopy, HPTLC, HPLC, LC-MS, GC, GC-MS, and electrochemical sensors, have been used for drug identification in pharmaceutical preparations and toxicological samples. The primary quantification techniques currently employed for its quantification in various matrices are highlighted in this research.

PHARMACOKINETICS OF TRAMADOL AND O-DESMETHYLTRAMADOL IN GIANT TORTOISES (CHELONOIDIS VANDENBURGHI, CHELONOIDIS VICINA)

The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (1 mg/kg and 5 mg/kg) and its metabolite, O-desmethyltramadol (M1) in giant tortoises (Chelonoidis vandenburghi, Chelonoidis vicina). Eleven giant tortoises (C. vandenburghi, C. vicina) received two randomly assigned, oral doses of tramadol (either 1 mg/kg or 5 mg/kg), with a washout period of 3 wk between each dose. The half-life (t½) of orally administered tramadol at 1 mg/kg and 5 mg/kg was 11.9 ± 4.6 h and 13.2 ± 6.1 h, respectively. After oral administration of tramadol at 1 mg/kg and 5 mg/kg, the maximum concentration (Cmax) was 125 ± 69 ng/ml and 518 ± 411 ng/ml, respectively. There were not enough data points to determine pharmacokinetic (PK) parameters for the M1 metabolite from either dose. Tramadol administered orally to giant tortoises at both doses provided measurable plasma concentrations of tramadol for approximately 48 h with occasional transient sedation. Oral tramadol at 5 mg/kg, on average, achieves concentrations of >100 ng/ml, the reported human therapeutic threshold, for 24 h. Based on the low levels of M1 seen in this study, M1 may not be a major metabolite in this taxon.

Preparation and evaluation of sublingual film of Ketorolac tromethamine

OBJECTIVE

This research aimed to formulate fast dissolving sublingual films of Ketorolac tromethamine to improve therapeutic efficacy, patient compliance and overcome the drug's gastrointestinal side effects by avoiding direct contact with the gastric mucosa.

METHODS

This research produced Ketorolac tromethamine sublingual film by solvent casting method using a variable ratio of polymer and plasticizer but a fixed quantity of other excipients and solvent ratio to evaluate the effect of these components on the overall formulation. Total 9 (F1 to F9) formulations were prepared where the ratio of Kollicoat®IR as polymer and Polyethylene glycol 400 as plasticizer were 2.0:1, 3.0:1, 4.0:1, 4.0:1, 4.8:1, 5.6:1, 5.33:1, 6.0:1, 6.66:1 respectively. The prepared films were evaluated through morphological and organoleptic properties, weight uniformity, folding endurance, surface pH, thickness, percentage of moisture loss, dispersion, dissolution and drug content uniformity. Also, API-excipients compatibility was evaluated by FTIR spectroscopy.

RESULTS

Formulation-2 (F2) demonstrated better film with optimum folding endurance where the ratio of Kollicoat^®IR and Polyethylene glycol 400 was 3.0:1. The film's surface and distribution of polymers and drugs was examined by trinocular microscopic imaging where drug molecule showed uniform distribution which was supported by the assay (100.1%) and content uniformity (100.1 ± 1.97%). Performed dissolution studies showed 99.3% drug dissolution occurred in just 3 minutes at pH 6.8.

CONCLUSION

Prepared films were found to have thin, fast dispersion and dissolution properties. Therefore, the patients can use the sublingual film to get rapid relief of pain with minimal side effects in the gastrointestinal tract.

Toxicokinetics of U-47700, tramadol, and their main metabolites in pigs following intravenous administration: is a multiple species allometric scaling approach useful for the extrapolation of toxicokinetic parameters to humans?

New synthetic opioids (NSOs) pose a public health concern since their emergence on the illicit drug market and are gaining increasing importance in forensic toxicology. Like many other new psychoactive substances, NSOs are consumed without any preclinical safety data or any knowledge on toxicokinetic (TK) data. Due to ethical reasons, controlled human TK studies cannot be performed for the assessment of these relevant data. As an alternative animal experimental approach, six pigs per drug received a single intravenous dose of 100 µg/kg body weight (BW) of U-47700 or 1000 µg/kg BW of tramadol to evaluate whether this species is suitable to assess the TK of NSOs. The drugs were determined in serum and whole blood using a fully validated method based on solid-phase extraction and LC–MS/MS. The concentration–time profiles and a population (pop) TK analysis revealed that a three-compartment model best described the TK data of both opioids. Central volumes of distribution were 0.94 L/kg for U-47700 and 1.25 L/kg for tramadol and central (metabolic) clearances were estimated at 1.57 L/h/kg and 1.85 L/h/kg for U-47700 and tramadol, respectively. The final popTK model parameters for pigs were upscaled via allometric scaling techniques. In comparison to published human data, concentration–time profiles for tramadol could successfully be predicted with single species allometric scaling. Furthermore, possible profiles for U-47700 in humans were simulated. The findings of this study indicate that unlike a multiple species scaling approach, pigs in conjunction with TK modeling are a suitable tool for the assessment of TK data of NSOs and the prediction of human TK data.

Pharmacokinetic profile of injectable tramadol in the koala (Phascolarctos cinereus) and prediction of its analgesic efficacy

Tramadol is used as an analgesic in humans and some animal species. When tramadol is administered to most species it undergoes metabolism to its main metabolites M1 or O-desmethyltramadol, and M2 or N-desmethyltramadol, and many other metabolites. This study describes the pharmacokinetic profile of tramadol when a single subcutaneous bolus of 2 mg/kg was initially administered to two koalas. Based on the results of these two koalas, subsequently 4 mg/kg as a single subcutaneous injection, was administered to an additional four koalas. M1 is recognised as an active metabolite and has greater analgesic activity than tramadol, while M2 is considered inactive. A liquid chromatography assay to quantify tramadol, M1 and M2 in koala plasma was developed and validated. Liquid chromatography-mass spectrometry confirmed that M1 had been identified. Additionally, the metabolite didesmethyltramadol was identified in chromatograms of two of the male koalas. When 4 mg/kg tramadol was administered, the median half-life of tramadol and M1 were 2.89 h and 24.69 h, respectively. The M1 plasma concentration remained well above the minimally effective M1 plasma concentration in humans (approximately 36 ng/mL) over 12 hours. The M1 plasma concentration, when tramadol was administered at 2 mg/kg, did not exceed 36 ng/mL at any time-point. When tramadol was administered at 2 mg/kg and 4 mg/kg the area under the curve M1: tramadol ratios were 0.33 and 0.50, respectively. Tramadol and M1 binding to plasma protein were determined using thawed, frozen koala plasma and the mean binding was 20% and 75%, respectively. It is concluded that when tramadol is administered at 4 mg/kg as a subcutaneous injection to the koala, it is predicted to have some analgesic activity.

Comparison of intraoperative cardiorespiratory and behavioral responses to medetomidine combined with tramadol or butorphanol during standing laparoscopic ovariectomy in horses

The purpose of this study was to assess the cardiorespiratory and behavioral responses to the combination of medetomidine and tramadol (M-T) or butorphanol (M-B) in standing laparoscopic ovariectomy in horses. One ovary was removed under M-T and the contralateral ovary was removed under M-B with at least 4 weeks between operations at random. Horses were sedated using intravenous medetomidine (5 µg/kg) followed by tramadol (1 mg/kg) or butorphanol (10 µg/kg) after 5 min. Sedation was maintained through the repeated injection of medetomidine (1 µg/kg) and tramadol (0.4 mg/kg) or medetomidine (1 µg/kg) and butorphanol (4 µg/kg) every 15 min. Cardiorespiratory function and behavioral responses, including, sedation, ataxia, and analgesia, were assessed during the surgery. There were no significant differences in cardiorespiratory values and sedation and analgesia scores between M-T and M-B. Ataxia scores were significantly lower in M-T than in M-B. This result suggests that M-T could maintain smooth and stable standing surgery with minimal cardiorespiratory changes in horses.

Pharmacokinetic properties of tramadol and M1 metabolite in Northeast Brazilian donkeys (Equus asinus)

There is currently little information available on the pharmacokinetics and pharmacodynamics of the analgesic opioid tramadol when used in the veterinary medicine of domestic species. In this study, we aimed to determine the pharmacokinetics of tramadol and its active metabolite M1 following intravenous administration of 2 (T2) and 4 (T4) mg/kg to Northeast Brazilian donkeys. Tramadol and M1 plasma levels were quantified using a validated liquid chromatography-tandem mass spectrometry method. We found that plasma levels of tramadol and M1 were higher than those reported as clinically meaningful in humans for at least 3 hr. However, the pharmacokinetic parameter calculation corrected by dose analysis identified no proportional increase with dose for the AUC of tramadol (T2: 2,663 ± 1,827 vs. T4: 2,964 ± 1,038 ng*h/ml) and M1 (T2: 378 ± 237 vs. T4: 345 ± 142 ng*h/ml). This finding appears to be attributable to a significant increase in clearance and a reduction in the terminal half-life of tramadol. The frequency of adverse effects observed at the higher dose indicates that 2 mg/kg administered intravenously would be suitable for donkeys. Clinical studies are required to determine the implications of these observations regarding the pharmacodynamic response to tramadol in Northeast Brazilian donkeys.

Tramadol Effects on Lameness Score After Inhibition of P-GP by Ivermectin Administration in Horses: Preliminary Results

This study aimed to evaluate the effects and lameness degree in horses administered tramadol after the P-glycoprotein (P-gp) enteric inhibitor ivermectin. Six horses were randomly distributed into three groups, which received two different doses of tramadol by a nasogastric tube: 1 mg/kg (tramadol group 1(GT1)), 4 mg/kg (tramadol group 4 (GT4)), and tramadol 1 mg/kg combined with ivermectin 0.2 mg/kg PO (ivermectin tramadol group (GT1 + Ive)), with one-week washout interval. Heart rate (HR), respiratory rate (RR), intestinal motility, body temperature, and the degree of lameness were evaluated for 360 minutes. The blood gas parameters were evaluated at 0, 60 minutes, and 120 minutes. There were no differences in HR and the degree of lameness. Hypomotility occurred in GT1 and GT4 only at the end of the evaluation period, and RR increased in all groups. We conclude that inhibition of enteric P-gp by ivermectin did not alter the effects of tramadol, suggesting that tramadol is not a substrate for P-gp. However, future studies should be conducted to assess the interaction between P-gp inhibitors on the pharmacokinetics of tramadol.

Effects of Orally Administered Resveratrol on TNF, IL-1β, Leukocyte Phagocytic Activity and Oxidative Burst Function in Horses: A Prospective, Randomized, Double-Blinded, Placebo-Controlled Study

Resveratrol, a phytophenol, is a commonly used equine nutraceutical supplement touted to exert anti-inflammatory effects. The effect of orally administered resveratrol on tumor necrosis factor (TNF), interleukin-1β (IL-1β), leukocyte phagocytic activity or oxidative burst function have not been reported in horses. The objective of this study was to determine the effects of a commercially available, orally administered resveratrol product on innate immune functions in healthy adult horses. Whole blood was collected from 12 horses prior to and following 3 weeks of treatment with either the manufacturer’s recommended dose of resveratrol or placebo. Phagocytosis, oxidative burst and pathogen associated molecular pattern (PAMP) motif-stimulated leukocyte production of TNF and IL-1β were compared pre- and post-treatment between treatment groups. Phagocytosis and oxidative burst capacity were evaluated via flow cytometry. Tumor necrosis factor and IL-1β were measured using cytotoxicity and ELISA assays, respectively. There were no significant differences in phagocytosis, oxidative burst or stimulated TNF or IL-1β production between resveratrol and placebo treatment groups. Orally administered resveratrol at a routinely recommended dose for a duration of 3 weeks did not significantly affect phagocytic activity, oxidative burst function or PAMP-stimulated leukocyte cytokine production.

BEVA primary care clinical guidelines: Analgesia

Primary care guidelines provide a reference point to guide clinicians based on a systematic review of the literature, contextualised by expert clinical opinion. These guidelines develop a modification of the GRADE framework for assessment of research evidence (vetGRADE) and applied this to a range of clinical scenarios regarding use of analgesic agents. Key guidelines produced by the panel included recommendations that horses undergoing routine castration should receive intratesticular local anaesthesia irrespective of methods adopted and that horses should receive NSAIDs prior to surgery (overall certainty levels high). Butorphanol and buprenorphine should not be considered appropriate as sole analgesic for such procedures (high certainty). The panel recommend the continuation of analgesia for 3 days following castration (moderate certainty) and conclude that phenylbutazone provided superior analgesia to meloxicam and firocoxib for hoof pain/laminitis (moderate certainty), but that enhanced efficacy has not been demonstrated for joint pain. In horses with colic, flunixin and firocoxib are considered to provide more effective analgesia than meloxicam or phenylbutazone (moderate certainty). Given the risk of adverse events of all classes of analgesic, these agents should be used only under the control of a veterinary surgeon who has fully evaluated a horse and developed a therapeutic, analgesic plan that includes ongoing monitoring for such adverse events such as the development of right dorsal colitis with all classes of NSAID and spontaneous locomotor activity and potentially ileus with opiates. Finally, the panel call for the development of a single properly validated composite pain score for horses to allow accurate comparisons between medications in a robust manner.

A review of recent developments in the pharmacological prevention and treatment of endocrinopathic laminitis

Despite the prevalence of endocrinopathic laminitis, the pharmacologic options for preventing and treating the disease are severely limited. The present review aims to discuss the spectrum of potential therapeutic agents for the condition, ranging from early experimental compounds to agents nearing registration. There are different pharmacologic targets for, and approaches to, managing laminitis. Reducing hyperinsulinaemia is central to diminishing endocrinopathic laminitis risk, and a detailed understanding of the pathophysiology of insulin dysregulation is necessary to identify pathways that can be targeted to minimise post-prandial insulin secretion and action. This area of research is advancing rapidly, with several exciting prospects, such as sodium-dependent glucose co-transporter-2 inhibitors, on the horizon for the treatment of equine metabolic dysfunction. Drugs that directly target the lamellae and aim to reduce the damage inflicted on the lamellae as part of this condition, are not yet available. Although progress in this area of laminitis therapy is slower, improved understanding of the events that lead to lamellar failure has enabled the investigation of novel drugs that aim to prevent laminitis at the site of the lesion. Finally, a brief review is included of the directions being taken in the management of the chronic and acute pain that accompanies laminitis. Medications for relieving the pain associated with laminitis are currently the most-prescribed drugs for the disease, and range from simple, affordable and thoroughly tested options, such as phenylbutazone, to newer, less-understood applications such as paracetamol and gabapentin. In the future, endocrinopathic laminitis management plans will likely take a multi-faceted approach that still hinge on effective dietary management and exercise, but also include drugs that address foot pathology, pain and underlying endocrine disturbances.

Intrinsic clearance rate of O-desmethyltramadol (M1) by glucuronide conjugation and phase I metabolism by feline, canine and common brush-tailed possum microsomes

Quantitative aspects of in vitro phase II glucuronidative metabolism of O-desmethyltramadol (O-DSMT or M1), the active metabolite of the analgesic drug tramadol, by feline, canine and common brush-tailed possum hepatic microsomes are described.Whilst previous studies have focused on the phase I conversion of tramadol to M1, this is the first report in which the phase II glucuronidative metabolic pathway of M1 has been isolated by an in vitro comparative species study.Using the substrate depletion method, microsomal phase II glucuronidative in vitro intrinsic clearance (Clint) of M1 was determined.The in vitro Clint (mean ± SD) by pooled common brush-tailed possum microsomes was 9.9 ± 1.7 μL/min/mg microsomal protein whereas the in vitro Clint by pooled canine microsomes was 1.9 ± 0.07 μL/min/mg microsomal protein. The rate of M1 depletion by feline microsomes, as measured solely by high pressure liquid chromatography, was too slow to determine. Liquid chromatography-mass spectrometry identified O-DSMT glucuronide in samples generated from all three species' microsomes, although the amount detected under the feline condition was minimal.This study indicates that M1 likely undergoes in vitro phase II glucuronidation by canine and common brush-tailed possum microsomes and, to a minor extent, by feline microsomes. The rate of depletion of M1 by phase I metabolism was also undertaken.When incubated with phase I co-factors and common brush-tailed possum microsomes or canine microsomes, M1 had an in vitro Clint of 47.6 and 22.8 μL/min/mg microsomal protein, respectively. However, due to a lack of CYP2B-like activity in the feline liver, unsurprisingly, M1 did not deplete when incubated with feline microsomes. Consequently, major M1 elimination pathways, using feline microsomes, were not determined."

Pharmacokinetics of single doses of maropitant citrate in adult horses

The neurokinin-1 (NK) receptor antagonist, maropitant citrate, mitigates nausea and vomiting in dogs and cats. Nausea is poorly understood and likely under-recognized in horses. Use of NK-1 receptor antagonists in horses has not been reported. The purpose of this study was to determine the pharmacokinetic profile of maropitant in seven adult horses after single intravenous (IV; 1 mg/kg) and intragastric (IG; 2 mg/kg) doses. A randomized, crossover design was performed. Serial blood samples were collected after dosing; maropitant concentrations were measured using LC-MS/MS. Pharmacokinetic parameters were determined using noncompartmental analysis. The mean plasma maropitant concentration 3 min after IV administration was 800 ± 140 ng/ml, elimination half-life was 10.37 ± 2.07 h, and volume of distribution was 6.54 ± 1.84 L/kg. The maximum concentration following IG administration was 80 ± 40 ng/ml, and elimination half-life was 9.64 ± 1.27 hr. Oral bioavailability was variable at 13.3 ± 5.3%. Maropitant concentrations achieved after IG administration were comparable to those in small animals. Concentrations after IV administration were lower than in dogs and cats. Elimination half-life was longer than in dogs and shorter than in cats. This study is the basis for further investigations into using maropitant in horses.

A influência da morfina ou tramadol pela via epidural no trânsito gastrintestinal de equinos

RESUMO Os opioides são utilizados na medicina veterinária na analgesia dos animais, porém há restrição quanto ao uso desses fármacos em equinos, pois podem desencadear alterações gastrintestinais, mas a administração pela via epidural minimiza os efeitos adversos. Assim, oito equinos hígidos foram utilizados em três grupos experimentais, objetivando-se avaliar a influência no trânsito gastrintestinal da injeção epidural de morfina (0,2mg/kg), tramadol (1,0mg/kg) ou NaCl 0,9%. Para a avaliação do trânsito gastrintestinal, foi administrada a lignina purificada e enriquecida (Lipe®), pela via oral, a qual posteriormente foi analisada nas fezes. As fezes foram coletadas para investigação desse marcador, antes da epidural e em intervalos até totalizar 48 horas do início do experimento. Os dados foram submetidos à análise de variância (ANOVA) de uma via, com repetições múltiplas. As médias entre cada momento dos grupos e dos momentos dentro de cada grupo foram comparadas pelo teste de Student-Newman-Keuls (P≤0,05). A morfina ou o tramadol administrados pela via epidural não alteraram o tempo médio de retenção da fase líquida, a taxa de passagem e o tempo de trânsito do marcador utilizado. Diante de tais achados, conclui-se que a morfina ou o tramadol pela via epidural não alteram o trânsito gastrintestinal.

Comparison of Analgesic Effects of a Constant Rate Infusion of Both Tramadol and Acetaminophen Versus those of Infusions of Each Individual Drug in Horses

The choice of analgesic agents for the horse is limited, and many have side effects that can restrict their use for chronic and prolonged pain. Little information has been published on tramadol and acetaminophen use in the horse. The study evaluated the analgesic effects of coadministration of tramadol and acetaminophen compared to those of each drug individually in a crossover study. The study was performed on six healthy horses each infused with the following over 1 hour: control (normal saline), tramadol, acetaminophen, or both (acetaminophen and tramadol infused together). Nociception (using a pressure algometer) and any adverse effects were evaluated before the infusion, at 0, 10, 20, 30, 40, and 50 minutes during the infusion and at 15, 30, and 60 minutes after infusion completion. The pressure algometer was placed on the palmar surface of both the forelimbs. There was no difference in response to nociception between the control and single-agent (acetaminophen or tramadol) groups. However, coadministration of tramadol and acetaminophen resulted in a significant analgesic effect from 20 minutes after starting the infusion until the infusion was completed. Fifteen minutes after discontinuing the infusion, no significant differences remained between the groups. No side effects were seen, with the exception of one horse in the coadministration group which showed paroxysmal ventricular tachycardia 30 minutes after constant rate infusion (CRI) which resolved completely after discontinuing the infusion. Simultaneous infusion of tramadol and acetaminophen resulted in significant analgesia. Further research is required to evaluate its effect and possible side effects in clinical cases, such as horses suffering from laminitis.

Preliminary pharmacokinetics of tramadol hydrochloride after administration via different routes in male and female B6 mice

OBJECTIVE

1) To determine the pharmacokinetics of tramadol hydrochloride and its active metabolite, O-desmethyltramadol (M1), after administration through different routes in female and male C57Bl/6 mice; 2) to evaluate the stability of tramadol solutions; and 3) to identify a suitable dose regimen for prospective clinical analgesia in B6 mice.

STUDY DESIGN

Prospective, randomized, blinded, parallel design.

ANIMALS

A total of 18 male and 18 female C57Bl/6 mice (20-30 g).

METHODS

Mice were administered 25 mg kg^-1 tramadol as a bolus [intravenously (IV), intraperitoneally (IP), subcutaneously (SQ), orally per gavage (OS_gavage)] over 25 hours [orally in drinking water (OS_water) or Syrspend SF (OS_Syrsp)]. Venous blood was sampled at six predetermined time points over 4 to 31 hours, depending on administration route, to determine tramadol and M1 plasma concentrations (liquid chromatography and tandem mass spectrometry detection). Pharmacokinetic parameters were described using a noncompartmental model. The stability of tramadol in water (acidified and untreated) and Syrspend SF (0.20 mg mL^-1) at ambient conditions for 1 week was evaluated.

RESULTS

After all administration routes, C_max was >100 ng mL^-1 for tramadol and >40 ng mL^-1 for M1 (reported analgesic ranges in man) followed by short half-lives (2-6 hours). The mean tramadol plasma concentration after self-administration remained >100 ng mL^-1 throughout consumption time. M1 was found in the OS_Syrs group only at 7 hours, whereas it was detectable in OS_water throughout administration. Tramadol had low oral bioavailability (26%). Short-lasting side effects were observed only after IV administration. Water and Syrspend SF solutions were stable for 1 week.

CONCLUSIONS AND CLINICAL RELEVANCE

1) At the dose administered, high plasma concentrations of tramadol and M1 were obtained, with half-life depending on the administration route. 2) Plasma levels were stable over self-consumption time. 3) Solutions were stable for 1 week at ambient conditions.

A physiologically based model for tramadol pharmacokinetics in horses

This work proposes an application of a minimal complexity physiologically based pharmacokinetic model to predict tramadol concentration vs time profiles in horses. Tramadol is an opioid analgesic also used for veterinary treatments. Researchers and medical doctors can profit from the application of mathematical models as supporting tools to optimize the pharmacological treatment of animal species. The proposed model is based on physiology but adopts the minimal compartmental architecture necessary to describe the experimental data. The model features a system of ordinary differential equations, where most of the model parameters are either assigned or individualized for a given horse, using literature data and correlations. Conversely, residual parameters, whose value is unknown, are regressed exploiting experimental data. The model proved capable of simulating pharmacokinetic profiles with accuracy. In addition, it provides further insights on un-observable tramadol data, as for instance tramadol concentration in the liver or hepatic metabolism and renal excretion extent.

Pain Management in Horses

There has been great progress in the understanding of basic neurobiologic mechanisms of pain, but this body of knowledge has not yet translated into new and improved analgesics. Progress has been made regarding pain assessment in horses, but more work is needed until sensitive and accurate pain assessment tools are available for use in clinical practice. This review summarizes and updates the knowledge concerning the cornerstones of pain medicine (understand, assess, prevent, and treat). It highlights the importance of understanding pain mechanisms and expressions to enable a rational approach to pain assessment, prevention, and management in the equine patient.

Anaesthetic effects of tiletamine-zolazepam-xylazine-tramadol combination in cats undergoing surgical sterilization

This study was conducted to evaluate the anaesthetic and physiological effects of tiletamine-zolazepam-xylazine-tramadol (TZXT) combination in cats undergoing surgical sterilization. A total of 20, 13.3 ± 2.5 months old, with a body weight of 2.4 ± 0.2 kg, male cats were used in the experiment. Cats were randomly assigned into the anaesthesia group (group A) or to the surgery group (group S). The tiletamine-zolazepam-xylazine-tramadol combination was administered with an intended dose of 2.4 mg·kg-1 tiletamine-zolazepam (TZ), 0.36 mg·kg-1 xylazine (X), and 0.8 mg·kg-1 tramadol (T) into the lateral femoral muscle. Physiological indicators including rectal temperature (RT), heart rate (HR), respiration rate (RR), haemoglobin saturation by oxygen (SpO2), mean arterial pressure (MAP), systolic arterial pressure (SAP), and diastolic arterial pressure (DAP) were collected after baseline values (time 0). Cats were immediately given the intramuscular injection drug combination. Physiological indicators were recorded before injection of this combination and at time 5, 10, 15, 20, 30, 40, 50, 60, 80, 100, and 120 min after administration of the tiletamine-zolazepam-xylazine-tramadol combination. In group S, castrations were performed using a closed procedure. Vomiting, excitement, apnoea, and abnormal behaviour were not observed in any cat during anaesthesia. All changes in indicators were within cardiorespiratory acceptable limits in both groups. The tiletamine-zolazepam-xylazine-tramadol combination produced satisfactory anaesthesia in cats and it will be useful not only in induction of anaesthesia but also for surgery of short duration.

Plasma concentrations, analgesic and physiological assessments in horses with chronic laminitis treated with two doses of oral tramadol

REASONS FOR PERFORMING STUDY

Laminitis is a painful disease for which adequate pain management remains a challenging and largely unmet medical need.

OBJECTIVES

To investigate plasma concentrations, analgesic and physiological effects of 2 doses of tramadol in horses with chronic laminitis.

STUDY DESIGN

Nonrandomised trial.

METHODS

Four horses with naturally occurring chronic laminitis received 5 mg/kg bwt and then 10 mg/kg bwt tramadol orally every 12 h for one week with a one-week washout between. Noninvasive arterial blood pressure, heart and respiratory rates, intestinal sounds and forelimb off-loading frequency were evaluated before and during treatments. Plasma tramadol and metabolite (M1 and M2) concentrations were measured on predetermined days and times after the morning dosing.

RESULTS

Forelimb off-loading frequency decreased significantly with 10 mg/kg bwt (40%, P = 0.02) but not with 5 mg/kg bwt (9%, P = 0.4). Physiological variables did not change significantly with either treatment. For 5 and 10 mg/kg bwt treatments, respectively, individual maximum plasma concentrations (μg/l) ranged from 329 to 728 and 628 to 1330 (tramadol), 12-24 and 32-80 (M1), and 90-157 and 239-362 (M2). Respective median area under the concentration vs. time curves (h μg/l) were 727 and 1426, 33 and 88, 303 and 1003.

CONCLUSIONS

Twice daily oral tramadol at 10 mg/kg bwt may produce analgesic plasma levels in horses with chronic laminitis.

Tramadol half life is dose dependent in overdose

Background

Tramalol overdose is disproportionately more common in Iran. In recent years, Tramadol overdose has become one of the most common causes of poisoning admissions to emergency departments in this country. To the best of our knowledge, there is little or no information regarding the toxicokinetic properties of Tramadol such as its half life. Given the fact that poisoning management should be based on the toxicokinetic of substances, we aimed at investigating the half life of Tramadol in man as a critical toxicokinetic variable in overdose.

Methods

Blood samples of each patient were collected on admission and repeated later. Plasma was harvested after separation from blood cells by centrifugation and quantified using HPLC method. Calculations were performed on Tramadol blood concentration quantities.

Findings

Demographic: Most of cases were men (81.81%). Mean (Standard Deviation (SD), min-max) age was 23 (8.142, 17-40). Serum Tramadol levels: Mean (SD, min-max) first Tramadol concentration was 786.91 (394.53, 391-1495). Mean (SD, min-max) second Tramadol concentration was 433.09 (269.63, 148-950). Mean (SD, min-max) of Tramadol half life was calculated as 9.24 hour (2.310, 4.99-13.45) Associations: Half life was associated with higher concentrations (r=0.708 Sig=0.015).

Conclusion

We report the mean half life of tramadol in overdose to be 9.24 hours which is remarkably higher than that measured in previous pharmacokinetic studies. We also concluded that Tramadol half life is dose dependent in overdose which may explain the further consequences of severe overdoses.

Anti-nociceptive and sedative effects of romifidine, tramadol and their combination administered intravenously slowly in ponies

OBJECTIVE

To evaluate the anti-nociceptive and sedative effects of slow intravenous (IV) injection of tramadol, romifidine, or a combination of both drugs in ponies.

STUDY DESIGN

Within-subject blinded.

ANIMALS

Twenty ponies (seven male, 13 female, weighing mean ± SD 268.0 ± 128 kg).

METHODS

On separate occasions, each pony received one of the following three treatments IV; romifidine 50 μg kg(-) (R) tramadol 3 mg kg(-1) given over 15 minutes (T) or tramadol 3 mg kg(-1) followed by romifidine 50 μg kg(-1) (RT). Physiologic parameters and caecal borborygmi (CB) were measured and sedation and response to electrical stimulation of the coronary band assessed before and up to 120 minutes following drugs administration. Results were analyzed using the Friedman's test and 2 way anova as relevant.

RESULTS

When compared to baseline, heart (HR, beats minute(-1) ) and respiratory rates (fR , breaths minute(-1) ) increased with treatment T (highest mean ± SD, HR 43 ± 1; fR 33 ± 2) and decreased with R (lowest HR 29 ± 1 and fR 10 ± 4) and RT (lowest HR 32 ± 1 and fR 9 ± 3). There were no changes in other measured physiological variables. The height of head from the ground was lower following treatments R and TR than T. There was slight ataxia with all three treatments. No excitatory behavioural effects were observed. The response to electrical stimulation was reduced for a prolonged period relative to baseline following all three treatments, the effect being significantly greatest with treatment RT.

CONCLUSION

Tramadol combined with romifidine at the stated doses proved an effective sedative and anti-nociceptive combination in ponies, with no unacceptable behavioural or physiologic side effects.

CLINICAL RELEVANCE

Slow controlled administration of tramadol should reduce the occurrence of adverse behavioural side effects.

Pharmacokinetics of tramadol and its primary metabolite O-desmethyltramadol in African penguins (Spheniscus demersus)

Analgesia is an important part of veterinary medicine, but until recently there have been limited studies on analgesic drugs in avian species. Tramadol represents an orally administered opioid drug that has shown analgesic potential in numerous species, including mammals, birds, and reptiles. The objective of this study was to determine the pharmacokinetic parameters of tramadol and its primary metabolite, O-desmethyltramadol (M1), after oral administration of tramadol hydrochloride (HCl) in African penguins (Spheniscus demersus). A dose of 10 mg/kg of tramadol HCl was administered orally to 15 birds, and blood was collected at various time points from 0 to 36 hr. Tramadol and M1 concentrations were determined and were consistent with therapeutic concentrations in humans through 12 hr in 9/15 birds for tramadol and 36 hr in 14/15 birds for M1. Based on these findings and a comparison with other avian studies, an oral dose of 10 mg/kg of tramadol once daily appears to be a promising analgesic option for African penguins.

Pharmacokinetics and physiological effects of repeated oral administrations of tramadol in horses

This study evaluated the pharmacokinetics and physiological effects of tramadol during repeated oral administrations in horses. Nine adult healthy horses were administered tramadol at 5 and 10 mg/kg orally every 12 h for 5 days in a randomized, crossover design with a 3-week washout between treatments. Plasma concentrations of tramadol, O- and N-desmethyltramadol (M1 and M2) were measured using Liquid-Chromatography-Mass Spectrometry at predetermined time points following each tramadol administration. Cardiovascular, respiratory and gastrointestinal physiological variables were monitored and adverse events were recorded. Data were analysed with two-way repeated measures anova or Kruskal-Wallis one-way anova on ranks with P < 0.05 considered statistically significant. There were no significant effects of tramadol on the physiological variables. One horse receiving 10 mg/kg tramadol developed mild colic. Following tramadol at 5 and 10 mg/kg, respectively, maximum plasma concentrations (Cmax ) of tramadol ranged from 82-587 and 127-1280 ng/mL, nonconjugated M1 ranged from 2.51-26.7 and 4.88-34.3 ng/mL, and nonconjugated M2 from 12.5-356 and 35.4-486 ng/mL. Corresponding minimum plasma concentrations (Cmin ) of tramadol at 12 h following each dose ranged from 0.8-24 and 3-117 ng/mL. Tramadol accumulated considerably over time, more markedly when given at 10 mg/kg than at 5 mg/kg (accumulation indexes of 3.51 and 1.73 respectively). There was no accumulation of M1 but substantial accumulation of M2. In conclusion, there was accumulation and increase in exposure to tramadol and M2, but not M1, during repeated oral administrations in horses.

Effects of tramadol with tiletamine/zolazepam-xylazine as anaesthesia in cats

This study was conducted to investigate the effect of the combination of tiletamine/zolazepam-xylazine-tramadol (TZXT) in cats and to compare its efficacy as an anaesthetic technique with tiletamine/zolazepam-xylazine (TZX). Fourteen healthy thirteen-month-old cats of both sexes were immobilized by TZXT or TZX on two different occasions. The cats’ scores for immobilization, analgesia and baseline physiological indicators, heart rate, respiratory rate and rectal temperature, were recorded before and 5, 10, 15, 20, 30, 40, 50, 60, 80, 100 and 120 min after administration of TZXT or TZX. Animals in both groups became laterally recumbent within 3 min and physiological indicators changed after administration. These changes were within biologically acceptable limits; these measurements did not differ between the treatments. Induction and recovery quality in animals was better with TZXT than with TZX. Sedation, analgesia, muscle relaxation and posture scores was higher in TZXT group. During recovery, cats in TZXT group were more conscious than cats in TZX group. This study showed that in cats, addition of tramadol (T) to TZX improved the quality of anaesthetic induction and increased the analgesic effect without adversely affecting the physiological indicators. Thus tiletamine/zolazepam-xylazine-tramadol shows to be more suitable for cat anaesthesia.

Anaesthesia and cardiopulmonary effects of tiletamine-zolazepam/xylazine/tramadol and its effects on nitric oxide, plasma endothelin, 6-keto-PGF1α and thromboxanes B2 in miniature pigs

This study focused on anaesthesia and cardiopulmonary effects of tiletamine-zolazepam/xylazine/tramadol in miniature pigs and its effects on endothelium-derived vasoactive factors. A total of 14 eight-month-old Chinese experimental miniature pigs were used in this study. Tiletamine-zolazepam (3.5 mg·kg-1), xylazine (1.32 mg·kg-1) and tramadol (1.8 mg·kg-1) were administered i.m.; blood pressure and heart rate were recorded. At the same time, blood was collected through precaval vein, and nitric oxide, endothelin, 6-keto-PGF1α and thromboxanes B2 were determined by colorimetry and radioimmunoassay. The mean times to dorsal recumbency, duration of immobilization, standing and walking were 2.26 ± 0.72, 87.57 ± 9.61, 25.63 ± 12.55 and 36.70 ± 14.53 min, respectively. Blood pressure was significantly changed at 10 and 80 min (P < 0.01), and the heart rate ranged from 89 to 134 bpm without episodes of severe bradycardia or tachycardia. Significantly positive correlation was observed between endothelin, thromboxanes B2 and blood pressure as well as the heart rate (P < 0.05). There was negative correlation between PGI2 and blood pressure as well as heart rate (P < 0.05). The results showed that endothelin, 6-keto-PGF1α and thromboxanes B2 participated in the changing of cardiopulmonary parameters which were caused by tiletamine-zolazepam-xylazine-tramadol anaesthesia in miniature pigs, and the 6-keto-PGF1α, ET and TXB2 concentrations in plasma participated in the changing of blood pressures during anaesthesia. Therefore, we can recommend tiletamine-zolazepam/xylazine/tramadol for anaesthesia in pigs, and this study also contributes to the evaluation of the effect of endothelium-derived vasoactive factors during anaesthesia.

Pharmacokinetics and selected pharmacodynamic effects of tramadol following intravenous administration to the horse

REASONS FOR PERFORMING STUDY

Both the potential analgesic effect and the conflicting reports describing tramadol disposition in the horse warrant further study of the pharmacokinetics of tramadol in this species.

OBJECTIVES

To describe the pharmacokinetics of tramadol and its metabolites, O-desmethyltramadol and N-desmethyltramadol, following i.v. administration of 3 doses to the horse.

METHODS

Nine adult horses received a single i.v. dose of 0.5, 1.5 and 3 mg/kg bwt tramadol. Blood samples were collected prior to and at various times up to 72 h post administration. Plasma samples were analysed using liquid chromatography-mass spectrometry and data analysed using noncompartmental analysis. Chin-to-ground distance, heart rate and rhythm, step count and gastrointestinal activity were also assessed.

RESULTS

Maximal measured plasma tramadol concentrations were 454 ± 101.6, 1086.7 ± 330.7 and 1697.9 ± 406.1 ng/ml for 0.5, 1.5 and 3 mg/kg bwt, respectively. Depending on the dose administered, the tramadol clearance, volume of distribution and half-life ranged from 24.6 to 25.0 ml/min/kg, 2.66 to 3.33 l/kg and 2.17 to 3.05 h, respectively. Following administration of 0.5, 1.5 and 3 mg/kg bwt tramadol, the maximal measured plasma concentrations of the active metabolite, O-desmethyltramadol, were 3.9 ± 1.9, 9.6 ± 4.8 and 12.9 ± 5.2 ng/ml, respectively. Muscle fasiculations and tremors were seen following administration of the 2 high doses. No significant changes in chin-to-ground distance, heart rate and rhythm, step count and gastrointestinal activity were observed.

CONCLUSIONS AND POTENTIAL RELEVANCE

This study confirms and extends previous studies describing the pharmacokinetics of tramadol following i.v. administration to the horse. Plasma tramadol concentrations exceeded those necessary for analgesia in human patients; however, further studies are necessary to determine plasma concentrations of tramadol necessary for analgesic efficacy in the horse. These results support further investigation of the analgesic efficacy of tramadol in the horse.

ADP-induced platelet aggregation after addition of tramadol in vitro in fed and fasted horses plasma

Adenosine diphosphate (ADP)-induced platelet aggregation in fed and fasted horses after addition of tramadol hydrochloride was evaluated in vitro. On 10 horses citrated blood samples were collected 2h after feeding (fed animals) and 21 h after feeding (fasted animals). Final concentrations of ADP 1 and 0.5 μM, and tramadol hydrochloride (1, 15, 30, 45 and 60 min after the addition of tramadol) were used to determine the maximum degree and initial velocity of platelet aggregation. Repeated measures multifactor analysis of variance (MANOVA) was used to evaluate the effect of feeding/fasting condition, ADP concentration and addition of tramadol. Findings showed statistical differences (P≤0.05) on studied parameters after addition of tramadol to different ADP concentrations in fed and fasted horses. The clinical relevance of these results is that tramadol provides many advantages as a therapeutic option; in fact, it is an inexpensive and a relatively new analgesic in equine veterinary medicine. Further investigations would be appropriate to compare the effects of different opioids but also using different concentrations of tramadol associated with other drugs in order to have substances which can regulate the functional activity of the platelets and to extend the knowledges on equine platelet aggregation.

Sedative and analgesic effects of intravenous xylazine and tramadol on horses

This study was performed to evaluate the sedative and analgesic effects of xylazine (X) and tramadol (T) intravenously (IV) administered to horses. Six thoroughbred saddle horses each received X (1.0 mg/kg), T (2.0 mg/kg), and a combination of XT (1.0 and 2.0 mg/kg, respectively) IV. Heart rate (HR), respiratory rate (RR), rectal temperature (RT), indirect arterial pressure (IAP), capillary refill time (CRT), sedation, and analgesia (using electrical stimulation and pinprick) were measured before and after drug administration. HR and RR significantly decreased from basal values with X and XT treatments, and significantly increased with T treatment (p < 0.05). RT and IAP also significantly increased with T treatment (p < 0.05). CRT did not change significantly with any treatments. The onset of sedation and analgesia were approximately 5 min after both X and XT treatments; however, the XT combination produced a longer duration of sedation and analgesia than X alone. Two horses in the XT treatment group displayed excited transient behavior within 5 min of drug administration. The results suggest that the XT combination is useful for sedation and analgesia in horses. However, careful monitoring for excited behavior shortly after administration is recommended.

In-vitro and in-vivo transdermal iontophoretic delivery of tramadol, a centrally acting analgesic

Objectives

The feasibility of transdermal delivery of tramadol, a centrally acting analgesic, by anodal iontophoresis using Ag/AgCl electrodes was investigated in vitro and in vivo.

Methods

To examine the effect of species variation and current strength on skin permeability of tramadol, in-vitro skin permeation studies were performed using porcine ear skin, guinea-pig abdominal skin and hairless mouse abdominal skin as the membrane. In an in-vivo pharmacokinetic study, an iontophoretic patch system was applied to the abdominal skin of conscious guinea pigs with a constant current supply (250 µA/cm2) for 6 h. An intravenous injection group to determine the pharmacokinetic parameters for estimation of the transdermal absorption rate in guinea pigs was also included.

Key findings

The in-vitro steady-state skin permeation flux of tramadol current-dependently increased without significant differences among the three different skin types. In the in-vivo pharmacokinetic study, plasma concentrations of tramadol steadily increased and reached steady state (336 ng/ml) 3 h after initiation of current supply, and the in-vivo steady-state transdermal absorption rate was 499 µg/cm2 per h as calculated by a constrained numeric deconvolution method.

Conclusions

The present study reveals that anodal iontophoresis provides current-controlled transdermal delivery of tramadol without significant interspecies differences, and enables the delivery of therapeutic amounts of tramadol.

Pharmacokinetics of tramadol and its major metabolites in alpacas following intravenous and oral administration

Tramadol, a centrally acting opioid analgesic with monamine reuptake inhibition, was administered to six alpacas (43-71 kg) randomly assigned to two treatment groups, using an open, single-dose, two-period, randomized cross-over design at a dose of 3.4-4.4 mg/kg intravenously (i.v.) and, after a washout period, 11 mg/kg orally. Serum samples were collected and stored at -80°C until assayed by HPLC. Pharmacokinetic parameters were calculated. The mean half-lives (t(1/2)) i.v. were 0.85±0.463 and 0.520±0.256 h orally. The Cp(0) i.v. was 2467±540 ng/mL, and the C(max) was 1202±1319 ng/mL orally. T(max) occurred at 0.111±0.068 h orally. The area under the curve (AUC(0-∞)) i.v. was 895±189 and 373±217 ng*h/mL orally. The volume of distribution (V(d[area])) i.v. was 5.50±2.66 L/kg. Total body clearance (Cl) i.v. was 4.62±1.09 h; Cl/F for oral administration was 39.5±23 L/h/kg. The i.v. mean residence time (MRT) was 0.720±0.264. Oral adsorption (F) was low (5.9-19.1%) at almost three times the i.v. dosage with a large inter-subject variation. This may be due to binding with the rumen contents or enzymatic destruction. Assuming linear nonsaturable pharmacokinetics and absorption processes, a dosage of 6.7 times orally would be needed to achieve the same i.v. serum concentration of tramadol. The t(1/2) of all three metabolites was longer than the parent drug; however, O-DMT, N-DMT, and Di-DMT metabolites were not detectable in all of the alpacas. Because of the poor bioavailability and adverse effects noted in this study, the oral administration of tramadol in alpacas cannot be recommended without further research.

Pharmacokinetics of tramadol hydrochloride and its metabolite O-desmethyltramadol in peafowl (Pavo cristatus)

Tramadol is a centrally acting opiate analgesic that has not been well studied in avian species. Tramadol and its metabolites exert their effects at multiple sites, including opiate (mu, kappa, and delta), adrenergic (alpha-2), and serotonin (5HT) receptors. This multi-receptor mode of action is advantageous for avian patients because the mechanisms for analgesia have not been fully elucidated in all species. The objective of this study was to document the pharmacokinetics of tramadol and its active metabolite O-desmethyltramadol (M1) in common peafowl (Pavo cristatus). Based on results from a pilot animal, six adult peafowl (three male, three female) judged to be clinically healthy based on physical exam and routine bloodwork were selected for this study. Each bird was anesthetized for placement of a jugular catheter, and 7.5 mg/kg tramadol was administered orally via gavage tube. Blood samples were collected just prior to drug administration; at 30 min; and at 1, 2, 3, 4, 6, 8, 10, 12, 24, and 34 hr. Plasma levels of tramadol and M1 were measured and the pharmacokinetics for each drug was calculated. Although tramadol was quickly metabolized, plasma levels of M1 remained at or near human analgesic levels for 12-24 hr. Based on these data, tramadol may be a practical option as an orally administered analgesic agent in avian patients. Further studies, including antinociceptive studies, are needed.

Tramadol use in zoologic medicine

Numerous analgesics are available for use in animals, but only a few have been used or studied in zoologic species. Tramadol is a relatively new analgesic that is available in an inexpensive, oral form, and is not controlled. Studies examining the effect of tramadol in zoologic species suggest that significant differences exist in pharmacokinetics parameters as well as analgesic dynamics. This article reviews the current literature on the use of tramadol in humans, domestic animals, and zoologic species.

Effect of the addition of tramadol to a combination of tiletamine-zolazepam and xylazine for anaesthesia of miniature pigs

This study investigated the effects of a combination of tiletamine-zolazepam and xylazine plus tramadol (TZXT) and compared the efficacy of this combination with that of tiletaminezolazepam and xylazine (TZX) for providing anaesthesia in Chinese experimental miniature pigs. Fourteen healthy, eight-month-old miniature pigs of both sexes were immobilised with TZXT or TZX on two different occasions. The pigs' immobilisation and analgesia scores and baseline physiological parameters (heart rate, respiratory rate, non-invasive systolic, diastolic and mean arterial blood pressures, arterial haemoglobin oxygen saturation and rectal temperature) were determined before and five, 10, 30, 45, 60, 80 and 100 minutes after the administration of TZXT or TZX. Pigs in both groups became laterally recumbent within three minutes. Some physiological parameters were changed after administration of the drug combinations, but they remained within biologically acceptable limits and were not significantly different between the two treatments. The use of TZXT resulted in better induction time and quality of recovery compared with TZX, with higher scores for sedation, analgesia, muscle relaxation, posture and auditory response. The animals were much calmer during recovery after TZXT immobilisation.

The effects of tramadol on electroencephalographic spectral parameters and analgesia in rats

The effects of different doses of tramadol on analgesia and electroencephalographic (EEG) spectral parameters were compared in rats. Saline or tramadol 5, 10, 20 or 40 mg/kg was administered. The degree of analgesia was evaluated by tail-flick latency, and the degree of seizure was measured using numerical seizure score (NSS). Additionally, band powers, median power frequency and spectral edge frequency 95 were measured to quantify the EEG response. All doses of tramadol produced spike-wave discharge. Tramadol significantly and dose-dependently increased the analgesia, but these effects did not correspond with the changes in the EEG spectral parameters. NSS significantly increased in the Tramadol 20 and 40 mg/kg treatment groups compared to the Control and TRA5 groups, and two rats given 40 mg/kg had convulsions. In conclusion, tramadol dose-dependently increased the analgesic effect, and the 10 mg/kg dose appears to be a reliable clinical dose for analgesia in rats, but dose-dependent increases in analgesia and seizure severity did not correlate with EEG spectral parameters.