Oxycodone concentrations in the central nervous system and cerebrospinal fluid after epidural administration to the pregnant ewe

Abstract The main sites of the analgesic action of oxycodone are the brain and spinal cord. The present study describes the concentrations of oxycodone and its metabolites in the brain and spinal cord after epidural administration to the ewe. Twenty pregnant ewes undergoing laparotomy were randomized into two groups to receive epidural oxycodone: infusion group (n = 10, 0.1 mg·kg−1 bolus followed by continuous infusion of 0.05 mg·kg−1·h−1 for five days) or repeated boluses group (n = 10, 0.2 + 2x0.1 mg·kg−1 bolus followed by a 0.2 mg·kg−1 bolus every 12 hours for five days). After five days of oxycodone administration, arterial blood samples were collected, the sheep were killed, and a CSF sample and tissue samples from the cortex, thalamus, cerebellum and spinal cord were obtained for the quantification of oxycodone and its main metabolites. The median plasma and CSF concentrations of oxycodone were 9.0 and 14.2 ng·mL−1 after infusion and 0.4 and 1.1 ng·mL−1 after repeated boluses. In the infusion group, the cortex, thalamus and cerebellum oxycodone concentrations were 4‐8 times higher and in the spinal cord 1310 times higher than in plasma. In the repeated boluses group, brain tissue concentrations were similar in the three areas, and in the spinal cord were 720 times higher than in plasma. Oxymorphone was the main metabolite detected, which accumulated in the brain and spinal cord tissue. In conclusion, first, accumulation of oxycodone and oxymorphone in the CNS was observed, and second, high spinal cord concentrations suggest that epidural oxycodone may provide segmental analgesia

Pharmacokinetics of buprenorphine in pregnant sheep after intravenous injection

Abstract Buprenorphine is a semi‐synthetic opioid, widely used in the maintenance treatment for opioid‐dependent pregnant women. Limited data exist on the pharmacokinetics of buprenorphine in pregnancy. We conducted a pharmacokinetic study to determine the pharmacokinetics of intravenous buprenorphine in pregnant sheep. Fourteen pregnant sheep in late gestation received 10 µg/kg of buprenorphine as an intravenous bolus injection. Plasma samples were collected up to 48 h after administration. Buprenorphine and its metabolite, norbuprenorphine, were quantified from plasma using a LC/MS/MS method, with lower limits of quantification of 0.01 µg/L and 0.04 µg/L for buprenorphine and norbuprenorphine, respectively. The pharmacokinetic parameters were calculated using noncompartmental analysis. The pharmacokinetic parameters, median (minimum−maximum), were Cmax 4.31 µg/L (1.93–15.5), AUCinf 2.89 h*µg/L (1.72–40.2), CL 3.39 L/h/kg (0.25–6.02), terminal t½ 1.75 h (1.07–31.0), Vss 8.04 L/kg (1.05–49.3). Norbuprenorphine was undetected in all plasma samples. The median clearance in pregnant sheep was higher than previously reported for nonpregnant sheep and human (male) subjects. Our sensitive analytical method was able to detect long terminal half‐lives for six subjects, and a wide between‐subject variability in the study population. Significance statement: Buprenorphine is widely used for the treatment of opioid use disorder in pregnancy. However, limited data exist on the pharmacokinetics of buprenorphine during pregnancy. As this type of study cannot be done in humans due to ethical reasons, we conducted a study in pregnant sheep. This study provides pharmacokinetic data on buprenorphine in pregnant sheep and helps us to understand the pharmacokinetics of the drug in humans

Maternal and fetal buprenorphine pharmacokinetics in pregnant sheep during transdermal patch dosing:buprenorphine pharmacokinetics in pregnant sheep

Abstract Background: Buprenorphine is used in the opioid maintenance treatment for opioid dependent patients, including pregnant women. Despite the wide use, limited data exists on buprenorphine pharmacokinetics and fetal exposure during pregnancy. The aim of our study was to determine the buprenorphine pharmacokinetics during transdermal patch dosing to pregnant sheep and, to determine the extent of transplacental transfer of buprenorphine to the fetus. Methods: Pregnant sheep in late gestation (n=50) received 20, 25 or 40 µg/h of buprenorphine as a 7-day extended-release transdermal patch. Plasma samples were collected from the ewe and the fetus on days 1–6, and buprenorphine and norbuprenorphine concentrations were determined. During the exposure period the sheep had a surgical procedure on the second day, a recovery phase, and an experimental procedure on the sixth day. In the experiment, hypoxia was induced under anesthesia for 18 sheep to investigate if decreased fetal pH would cause ion-trapping of buprenorphine in the fetus. The fetal/maternal plasma concentration ratio was determined on the second and on the sixth exposure day at baseline and during hypoxia. Maternal pharmacokinetics were modelled with a population pharmacokinetic method using the data from this study and our previous intravenous administration study. Results: The transdermal patch provided an extended release of buprenorphine throughout the exposure period, but the release rate declined approximately 20 h after patch placement. The median fetal/maternal plasma concentration ratio was 13–27 % throughout the exposure period at baseline. A ratio over 100 % was observed for four sheep on the sixth exposure day (102–269 %). A minor increase was seen in the median fetal/maternal-ratios during maternal hypoxia. Norbuprenorphine was undetected in all plasma samples. Conclusions: The low transplacental passage of less than one fourth of the ewe’s exposure supports buprenorphine as an alternative to methadone in opioid maintenance therapy during pregnancy

Central nervous system distribution of buprenorphine in pregnant sheep, fetuses and newborn lambs after continuous transdermal and single subcutaneous extended-release dosing

Abstract Buprenorphine is used during pregnancy for the treatment of opioid use disorder. Limited data exist on the central nervous system (CNS) permeation and distribution, and on the fetal exposure to buprenorphine. The aim of our study was to determine the extent of buprenorphine distribution to CNS in the pregnant sheep, and their fetus at steady-state, and their newborn lambs postdelivery, using three different dosing regimens. Twenty-eight pregnant ewes in late gestation received buprenorphine via 7-day transdermal patch releasing buprenorphine 20 µg/h (n=9) or 40 µg/h (n=11), or an extended-release 8 mg/week subcutaneous injection (n=8). Plasma, cerebrospinal fluid, and CNS tissue samples were collected at steady-state from ewes and fetuses, and from lambs 0.33–45 hours after delivery. High accumulation of buprenorphine was observed in all CNS tissues. The median CNS/plasma concentration -ratios of buprenorphine in different CNS areas ranged between 13 and 50 in the ewes, and between 26 and 198 in the fetuses. In the ewes the CNS/plasma -ratios were similar after the three dosing regimens, but higher in the fetuses in the 40 µg/h dosing group, medians 65–122, than in the 20 µg/h group, medians 26–54. The subcutaneous injection (theoretical release rate 47.6 µg/h) produced higher concentrations than observed after 40 µg/h transdermal patch dosing. The median fetal/maternal concentration -ratios in different dosing groups ranged between 0.21 and 0.54 in plasma, and between 0.38 and 1.3 in CNS tissues, respectively, with the highest ratios observed in the spinal cord. Buprenorphine concentrations in the cerebrospinal fluid were 8–13 % of the concurrent plasma concentration in the ewes and 28 % in the fetuses. Buprenorphine was quantifiable in the newborn lambs’ plasma and CNS tissues two days postdelivery. Norbuprenorphine was analyzed from all plasma, cerebrospinal fluid, and CNS tissue samples but was nondetectable or below the LLOQ in most. The current study demonstrates that buprenorphine accumulates into CNS tissues at much higher concentrations than in plasma in pregnant sheep, fetuses, and their newborn lambs even 45 hours after delivery

MMP-3 and MMP-8 in rat mandibular condylar cartilage associated with dietary loading, estrogen level, and aging

Abstract Objectives: The structure of the mandibular condylar cartilage (MCC) is regulated by dynamic and multifactorial processes. The aim of this study was to examine the effects of altered dietary loading, estrogen level, and aging on the structure of the condylar cartilage and the expressions of matrix metalloproteinase (MMP) -3 and MMP-8 of rat MCC. Methods: In this study, Crl:CD (SD) female rats were randomly divided into 3 groups according to dietary hardness: hard diet (diet board), normal diet (pellet), and soft diet (powder). In each group, the rats were further divided into 2 subgroups by ovariectomy at the age of 7 weeks. The rats were sacrificed at 5- and 14-month-old. Histomorphometric analysis of the MCC thickness was performed after toluidine blue staining. Immunochemical staining was done for MMP-3 and MMP-8. A linear mixed model was used to assess the effects of dietary loading, estrogen level, and aging. Results: Increased dietary loading was the main factor to increase the MMP-3 expression and the anterior and central thickness of the MCC. Lack of estrogen was the main factor associated with decreased MMP-8. Aging was associated with the thickness changes of the whole condylar cartilage and the reduced expression of MMP-8. Conclusion: The condylar cartilage structure and metabolism of the female rats are sensitive to dietary loading changes, estrogen level as well as aging. The proper balance of these factors seems to be essential for the maintenance of the condylar cartilage

Behaviour, stress and welfare of Sprague Dawley rats (Rattus norvegicus) on diet board feeding for 24 months

Abstract Diet board (DB) feeding aims to reduce the health hazards associated with ad libitum (AL) feeding. Rats have to gnaw wood to detach food from the DB, reducing their food consumption. We studied the welfare effects of DB by measuring faecal corticosterone metabolites (FCM), elevated plus-maze (EPM) behaviour and cage behaviour. In this two-year experiment, 147 group housed (n = 3) Hsd:Sprague Dawley® male and female rats were subjected to DB or AL feeding. DB feeding in females elevated FCMs and increased eating observations by 85%. The DB males were observed eating 30% more often and resting 4.2% less than their AL counterparts. The DB rats of both sexes had 19% increased cage exploration during daytime and 20% reduced grooming during night-time compared to the AL rats. The increased FCMs may indicate slight stress in DB females. The EPM results indicate there was no anxiety due to DB feeding at six months. The cage behaviour could point to mild chronic stress in DB rats, but the lack of effect on escape-related behaviour and agonism suggests that there were no substantial welfare problems. DB feeding did not seem to disturb the circadian rhythm. The smaller food requirements of DB females meant they had to sacrifice less time than males gnawing at the DB to satisfy their appetite

Foramen ovale blood flow and cardiac function after main pulmonary artery occlusion in fetal sheep

Abstract The foramen ovale (FO) accounts for the majority of fetal left ventricular (LV) output. Increased right ventricular afterload can cause a redistribution of combined cardiac output between the ventricles. To understand the capability of the FO to increase its volume blood flow and thus LV output, we mechanically occluded the main pulmonary artery in seven chronically instrumented near‐term sheep fetuses. We hypothesized that FO volume blood flow and LV output would increase during main pulmonary artery occlusion. Fetal cardiac function and haemodynamics were assessed by pulsed and tissue Doppler at baseline, 15 and 60 min after occlusion of the main pulmonary artery and 15 min after occlusion was released. Fetal ascending aorta and central venous pressures and blood gas values were monitored. Main pulmonary artery occlusion initially increased fetal heart rate (P < 0.05) from [mean (SD)] 158 (7) to 188 (23) beats min⁻¹ and LV cardiac output (P < 0.0001) from 629 (198) to 776 (283) ml min⁻¹. Combined cardiac output fell (P < 0.0001) from 1524 (341) to 720 (273) ml min⁻¹. During main pulmonary artery occlusion, FO volume blood flow increased (P < 0.001) from 507 (181) to 776 (283) ml min⁻¹. This increase was related to fetal tachycardia, because LV stroke volume did not change. Fetal ascending aortic blood pressure remained stable. Central venous pressure was higher (P < 0.05) during the occlusion than after it was released. During the occlusion, fetal pH decreased and PCO₂ increased. Left ventricular systolic dysfunction developed while LV diastolic function was preserved. Right ventricular systolic and diastolic function deteriorated after the occlusion. In conclusion, the FO has a limited capacity to increase its volume blood flow at near‐term gestation

A single intra-articular dose of vitamin D analog calcipotriol alleviates synovitis without adverse effects in rats

Abstract 1,25-dihydroxyvitamin-D₃ and its derivatives have shown anti-arthritic and chondroprotective effects in experimental animal models with prophylactic dosing. The purpose of this preliminary study was to test the efficacy and safety of calcipotriol, vitamin D analog, as a treatment for a fully-developed knee arthritis in Zymosan-induced arthritis (ZIA) model. Forty 5-month-old male Sprague-Dawley rats were randomized into three arthritis groups and a non-arthritic control group with no injections (10 rats/group). A day after Zymosan (0.1 mg) had been administrated into the right knee joints, the same knees were injected with calcipotriol (0.1 mg/kg), dexamethasone (0.1 mg/kg) or vehicle in a 100 μl volume. The left control knees were injected with saline (PBS) on two consecutive days. All injections, blood sampling and measurements were performed under general anesthesia on days 0, 1, 3 and 8. Internal organs and knees were harvested on day 8 and the histology of the whole knees was assessed blinded. Joints treated with calcipotriol showed a milder histological synovitis than those treated with vehicle (p = 0.041), but there was no statistically significant difference between the dexamethasone and vehicle groups. The clinical severity of arthritis did not differ between the arthritis groups measured by body temperature, swelling of the knee, thermal imaging, clinical scoring or cytokine levels on days 1, 3 and 8. Weight loss was bigger in rats treated with dexamethasone, propably due to loss of appetite,compared to other arthritis groups on days 2–3 (p<0.05). Study drugs did not influence serum calcium ion and glucose levels. Taken together, this preliminary study shows that a single intra-articular injection of calcipotriol reduces histological grade of synovitis a week after the local injection, but dexamethasone did not differ from the vehicle. Calcipotriol may have an early disease-modifying effect in the rat ZIA model without obvious side effects

Pharmacokinetics of intra-articular vitamin D analogue calcipotriol in sheep and metabolism in human synovial and mesenchymal stromal cells

Abstract Calcipotriol (MC903) is a side chain analogue of the biologically active 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃]. Due to its anti-inflammatory and anti-proliferative effects on stromal cells, calcipotriol is a promising candidate for the local treatment of arthritis. In this preliminary work, we studied the pharmacokinetics and safety of calcipotriol after an IV (0.1 mg/kg given to one sheep) and intra-articular dose (0.054 mg/kg, 0.216 mg/kg and 0.560 mg/kg given to three sheep). The terminal half-life of calcipotriol was approximately 1 h after an IV dose. After intra-articular dosing, the systemic absorption was between 1 and 13% during the observed 24 h. Hypercalcemia or other clinical adverse effects did not occur in any animal during the study, and no macroscopic or microscopic alterations were seen in the synovium of the calcipotriol-injected knees compared to the vehicle knees. The in vitro metabolism of calcipotriol was analyzed with LC–MS from human synovial and mesenchymal stromal cell cultures. Both cell types were able to metabolize calcipotriol with MC1080 and MC1046 as the main metabolites. CYP24A1 transcripts were strongly induced by a 48-hour calcipotriol exposure in mesenchymal stromal cells, but not consistently in synovial stromal cells, as determined by RT-qPCR. Calcipotriol proved to be safe after a single intra-articular dose with applied concentrations, and it is metabolized by the cells of the joint. Slow dissolution of calcipotriol crystals in the joint can extend the pharmaceutical impact on the synovium, cartilage and subcortical bone