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Information on the pharmacokinetics (PK) and pharmacodynamics (PD) of orally administered cannabis‐based medicine (CBM) in capsule formulation in patient populations is sparse. In this exploratory study, we aimed to evaluate the PK and PD in a probable steady state of CBM in neuropathic pain and spasticity in a population of patients with multiple sclerosis (MS). Of 134 patients participating in a randomized, double‐blinded, placebo‐controlled, trial, 23 patients with MS (17 female) mean age 52 years (range 21–67) were enrolled in this substudy. They received oral capsules containing Δ9‐tetrahydrocannabinol (THC, n = 4), cannabidiol (CBD, n = 6), a combination (THC&CBD, n = 4), or placebo (n = 9). Maximum doses were 22.5 mg (THC) and 45 mg (CBD) a day divided into three administrations. PD parameters were evaluated for pain and spasticity. Blood samples were analyzed using an ultra‐high‐performance liquid chromatography–tandem mass spectrometer after protein precipitation and phospholipid removal. PK parameters were estimated using computerized modeling. The variation in daily dose and PK between individuals was considerable in a steady state, yet comparable with previous reports from healthy controls. Based on a simulation of the best model, the estimated PK parameters (mean) for THC (5 mg) were Cmax 1.21 ng/mL, Tmax 2.68 h, and half‐life 2.75 h, and for CBD (10 mg) were Cmax 2.67 ng/mL, Tmax 0.10 h, and half‐life 4.95 h, respectively. No effect was found on the PD parameters, but the placebo response was considerable. More immediate adverse events were registered in the active treatment groups compared with the placebo group. [ABSTRACT FROM AUTHOR]

Background and Purpose: Studies using intermittent‐access drug self‐administration show increased motivation to take and seek cocaine and fentanyl, relative to continuous access. In this study, we examined the effects of intermittent‐ and continuous‐access self‐administration on heroin intake, patterns of self‐administration and cue‐induced heroin‐seeking, after forced or voluntary abstinence, in male and female rats. We also modelled brain levels of heroin and its active metabolites. Experimental Approach Rats were trained to self‐administer a palatable solution and then heroin (0.075 mg·kg−1 per inf) either continuously (6 h·day−1; 10 days) or intermittently (6 h·day−1; 5‐min access every 30‐min; 10 days). Brain levels of heroin and its metabolites were modelled using a pharmacokinetic software. Next, heroin‐seeking was assessed after 1 or 21 abstinence days. Between tests, rats underwent either forced or voluntary abstinence. The oestrous cycle was measured using a vaginal smear test. Key Results: Intermittent access exacerbated heroin self‐administration and was characterized by a burst‐like intake, yielding higher brain peaks of heroin and 6‐monoacetylmorphine concentrations. Moreover, intermittent access increased cue‐induced heroin‐seeking during early, but not late abstinence. Heroin‐seeking was higher in females after intermittent, but not continuous access, and this effect was independent of the oestrous cycle. Conclusions and Implications: Intermittent heroin access in rats resembles critical features of heroin use disorder: a self‐administration pattern characterized by repeated large doses of heroin and higher relapse vulnerability during early abstinence. This has significant implications for refining animal models of substance use disorder and for better understanding of the neuroadaptations responsible for this disorder. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc [ABSTRACT FROM AUTHOR]

We have previously demonstrated that heroin's first metabolite, 6-acetylmorphine (6-AM), is an important mediator of heroin's acute effects. However, the significance of 6-AM to the rewarding properties of heroin still remains unknown. The present study therefore aimed to examine the contribution of 6-AM to heroin-induced reward and locomotor sensitization. Mice were tested for conditioned place preference (CPP) induced by equimolar doses of heroin or 6-AM (1.25-5 μmol/kg). Psychomotor activity was recorded during the CPP conditioning sessions for assessment of drug-induced locomotor sensitization. The contribution of 6-AM to heroin reward and locomotor sensitization was further examined by pretreating mice with a 6-AM specific antibody (anti-6-AM mAb) 24 hours prior to the CPP procedure. Both heroin and 6-AM induced CPP in mice, but heroin generated twice as high CPP scores compared with 6-AM. Locomotor sensitization was expressed after repeated exposure to 2.5 and 5 μmol/kg heroin or 6-AM, but not after 1.25 μmol/kg, and we found no correlation between the expression of CPP and the magnitude of locomotor sensitization for either opioid. Pretreatment with anti-6-AM mAb suppressed both heroin-induced and 6-AM-induced CPP and locomotor sensitization. These findings provide evidence that 6-AM is essential for the rewarding and sensitizing properties of heroin; however, heroin caused stronger reward compared with 6-AM. This may be explained by the higher lipophilicity of heroin, providing more efficient drug transfer to the brain, ensuring rapid increase in the brain 6-AM concentration. [ABSTRACT FROM AUTHOR]

Toll-like receptor 4 (TLR4) signaling is implied in opioid reinforcement, reward, and withdrawal. Here, we explored whether TLR4 signaling is involved in the acute psychomotor-stimulating effects of heroin, 6-acetylmorphine (6-AM), and morphine as well as whether there are differences between the three opioids regarding TLR4 signaling. To address this, we examined how pretreatment with (+)-naloxone, a TLR4 active but opioid receptor (OR) inactive antagonist, affected the acute increase in locomotor activity induced by heroin, 6-AM, or morphine in mice. We also assessed the effect of pretreatment with (-)-naloxone, a TLR4 and OR active antagonist, as well as the pharmacokinetic profiles of (+) and (-)-naloxone in the blood and brain. We found that (-)-naloxone reduced acute opioid-induced locomotor activity in a dose-dependent manner. By contrast, (+)-naloxone, administered in doses assumed to antagonize TLR4 but not ORs, did not affect acute locomotor activity induced by heroin, 6-AM, or morphine. Both naloxone isomers exhibited similar concentration versus time profiles in the blood and brain, but the brain concentrations of (-)-naloxone reached higher levels than those of (+)-naloxone. However, the discrepancies in their pharmacokinetic properties did not explain the marked difference between the two isomers' ability to affect opioid-induced locomotor activity. Our results underpin the importance of OR activation and do not indicate an apparent role of TLR4 signaling in acute opioid-induced psychomotor stimulation in mice. Furthermore, there were no marked differences between heroin, 6-AM, and morphine regarding involvement of OR or TLR4 signaling., (U.S. Government work not protected by U.S. copyright.)