Pharmacokinetics and pharmacodynamics of intranasal and intramuscular administration of naloxone in working dogs administered fentanyl

BACKGROUND

Working dogs exposed to narcotics might require reversal in the field.

OBJECTIVE

To explore the pharmacokinetic and pharmacodynamic effects of naloxone administered intramuscularly (IM) or intranasally (IN) to reverse fentanyl sedation in working dogs.

ANIMALS

Ten healthy, working dogs aged 1.7 ± 1 year and weighing 26 ± 3 kg.

METHODS

In this randomized, controlled cross-over study dogs received either 4 mg of naloxone IN or IM 10 minutes after fentanyl (0.3 mg IV) administration. Sedation was assessed at baseline and 5 minutes after fentanyl administration, then at 5, 10, 15, 20, 25, 30, 60 and 120 minutes after reversal with naloxone. Blood samples for naloxone detection were obtained at 0, 5, 10, 30, 60 and 120 minutes. Pharmacokinetic parameters and sedation scores were compared between IM and IN naloxone groups.

RESULTS

There was a significant increase in sedation score from baseline (0.25 [-4 to 1] IM; 0 [-2 to 1] IN) after fentanyl administration (11 [5-12] IM; 9.25 [4-11] IN), followed by a significant reduction at 5 (0.5 [-0.5 to 1.5] IM; 1.25 [-1.5 to 4.5] IN) through 120 minutes (-0.5 [-2 to 1] IM; 0 [-4.5 to 1] IN) after reversal with naloxone. Route of administration had no significant effect on sedation score. Maximum plasma concentration was significantly lower after IN administration (11.7 [2.8-18.8] ng/mL IN, 36.7 [22.1-56.4] ng/mL IM, P < .001) but time to reach maximum plasma concentration was not significantly different from IM administration.

CONCLUSION AND CLINICAL IMPORTANCE

Although IM administration resulted in higher naloxone plasma concentrations compared to IN, reversal of sedation was achieved via both routes after administration of therapeutic doses of fentanyl.

FLASH proton radiotherapy spares normal epithelial and mesenchymal tissues while preserving sarcoma response

In studies of electron and proton radiotherapy, ultrahigh dose rates of FLASH radiation therapy appear to produce fewer toxicities than standard dose rates while maintaining local tumor control. FLASH-proton radiotherapy (F-PRT) brings the spatial advantages of PRT to FLASH dose rates (>40 Gy/sec), making it important to understand if and how F-PRT spares normal tissues while providing anti-tumor efficacy that is equivalent to standard-proton radiotherapy (S-PRT). Here we studied PRT damage to skin and mesenchymal tissues of muscle and bone and found that F-PRT of the C57BL/6 murine hind leg produced fewer severe toxicities leading to death or requiring euthanasia than S-PRT of the same dose. RNAseq analyses of murine skin and bone revealed pathways upregulated by S-PRT yet unaltered by F-PRT, such as apoptosis signaling and keratinocyte differentiation in skin, as well as osteoclast differentiation and chondrocyte development in bone. Corroborating these findings, F-PRT reduced skin injury, stem cell depletion, and inflammation, mitigated late effects including lymphedema, and decreased histopathologically detected myofiber atrophy, bone resorption, hair follicle atrophy, and epidermal hyperplasia. F-PRT was equipotent to S-PRT in control of two murine sarcoma models, including at an orthotopic intramuscular site, thereby establishing its relevance to mesenchymal cancers. Finally, S-PRT produced greater increases in TGF-β1 in murine skin and the skin of canines enrolled in a phase 1 study of F-PRT versus S-PRT. Collectively, these data provide novel insights into F-PRT-mediated tissue sparing and support its ongoing investigation in applications that would benefit from this sparing of skin and mesenchymal tissues.

Facilitative ecological interactions between invasive species: Arundo donax stands as favorable habitat for cattle ticks (Acari: Ixodidae) along the U.S.-Mexico border

The cattle tick, Rhipicephalus (Boophilus) spp. is a key vector of protozoa that cause bovine babesiosis. Largely eradicated from most of the United States, the cattle tick continues to infest south Texas, and recent outbreaks in this area may signal a resurgence of cattle tick populations despite current management efforts. An improved understanding of the dynamic ecology of cattle fever ticks along the U.S.-Mexico border is required to devise strategies for sustainable eradication efforts. Management areas of the cattle tick overlap considerably with dense, wide infestations of the non-native, invasive grass known as giant reed (Arundo donax L.). Here we show that stands of giant reed are associated with abiotic and biotic conditions that are favorable to tick survival, especially when compared with other nearby habitats (open pastures of buffelgrass (Pennisetum ciliare) and closed canopy native forests). Overhead canopies in giant reed stands and native riparian forests reduce daily high temperature, which was the best abiotic predictor of oviposition by engorged females. In sites where temperatures were extreme, specifically open grasslands, fewer females laid eggs and the resulting egg masses were smaller. Pitfall trap collections of ground dwelling arthropods suggest a low potential for natural suppression of tick populations in giant reed stands. The finding that A. donax infestations present environmental conditions that facilitate the survival and persistence of cattle ticks, as well or better than native riparian habitats and open grasslands, represents an alarming complication for cattle fever tick management in the United States.

Intra-articular load distribution in the human ankle joint during motion

The rational treatment of injuries to the ankle is predicated on an understanding of biomechanics of the ankle. While several investigators have reported on three-dimensional dynamic kinematics of the ankle and on the static distribution of pressure within the ankle, it has not been possible to measure intra-articular forces reliably under dynamic conditions. The assumption that the distribution of forces under dynamic conditions is well represented by statically determined forces has not been validated, leaving in question the applicability to dynamic conditions of data obtained under static conditions. This study characterizes an electro-mechanical thin-membrane force transducer with potential for intra-articular use. The sensor was found to yield a reproducible linear response to loads experienced in the ankle, and was insensitive to both a moist environment and shearing forces. On the basis of these results, these force-transducers were placed in axially loaded cadaveric ankles that were either statically or dynamically cycled through a physiologic range of motion. In each of six specimens, sensors were secured to the medial and lateral malleolar articular surfaces, and to articular surfaces of the medial and lateral tibial plafond. Both medial and lateral malleolar-talar forces increased with dorsiflexion. Moving from plantarflexion to dorsiflexion caused an increase in lateral tibio-talar load accompanied by a decrease in the medial tibio-talar loading. There was no significant hysteresis in force-distribution with respect to the direction of sagittal motion. There was no difference between the forces measured under static or dynamic conditions. This study validates the use of static loading methodologies in future studies of force-distribution. Our data in intact ankles closely corresponded to data on forces under dynamic conditions. Dorsiflexion caused an increase in both medially and laterally directed forces towards the malleoli. This is the first demonstration of such forces, which are responsible for the external rotation and lateral translation of the distal fibula that occurs in dorsiflexion of the ankle.