Cannabis, or marijuana, has been used for medicinal purposes for many years. Several types of cannabinoid medicines are available in the United States and Canada. Dronabinol (schedule III), nabilone (schedule II), and nabiximols (not U.S. Food and Drug Administration approved) are cannabis-derived pharmaceuticals. Medical cannabis or medical marijuana, a leafy plant cultivated for the production of its leaves and flowering tops, is a schedule I drug, but patients obtain it through cannabis dispensaries and statewide programs. The effect that cannabinoid compounds have on the cannabinoid receptors (CB(1) and CB(2) ) found in the brain can create varying pharmacologic responses based on formulation and patient characteristics. The cannabinoid Δ(9) -tetrahydrocannabinol has been determined to have the primary psychoactive effects; the effects of several other key cannabinoid compounds have yet to be fully elucidated. Dronabinol and nabilone are indicated for the treatment of nausea and vomiting associated with cancer chemotherapy and of anorexia associated with weight loss in patients with acquired immune deficiency syndrome. However, pain and muscle spasms are the most common reasons that medical cannabis is being recommended. Studies of medical cannabis show significant improvement in various types of pain and muscle spasticity. Reported adverse effects are typically not serious, with the most common being dizziness. Safety concerns regarding cannabis include the increased risk of developing schizophrenia with adolescent use, impairments in memory and cognition, accidental pediatric ingestions, and lack of safety packaging for medical cannabis formulations. This article will describe the pharmacology of cannabis, effects of various dosage formulations, therapeutics benefits and risks of cannabis for pain and muscle spasm, and safety concerns of medical cannabis use.

Benzodiazepines are effective short-term treatments for anxiety disorders, but their use is limited by undesirable side effects related to Central Nervous System impairment and tolerance development. SL65.1498 is a new compound that acts in vitro as a full agonist at the gamma-aminobutyric acid(A) 2 and 3 receptor and as a partial agonist at the 1 and 5 receptor subtypes. It is thought that the compound could be anxiolytic by its activation at the alpha2 and alpha3 receptor subtypes, without causing unfavourable side effects, which are believed to be mediated by the alpha1 and alpha5 subtypes. This study was a double-blind, five-way cross-over study to investigate the effects of three doses of SL65.1498 in comparison with placebo and lorazepam 2 mg in healthy volunteers. The objective was to select a dose level (expected to be therapeutically active), free of any significant deleterious effect. Psychomotor and cognitive effects were measured using a validated battery of measurements, including eye movements, body sway, memory tests, reaction-time assessments, and visual analogue scales. The highest dose of SL65.1498 showed slight effects on saccadic peak velocity and smooth pursuit performance, although to a much lesser extent than lorazepam. In contrast to lorazepam, none of the SL65.1498 doses affected body sway, visual analogue scale alertness, attention, or memory tests. This study showed that the three doses of SL65.1498 were well tolerated and induced no impairments on memory, sedation, psychomotor, and cognitive functions.

In this study, the hypothesis that haloperidol would lead to an amelioration of Δ9-tetrahydrocannabinol (THC)-induced 'psychotomimetic' effects was investigated. In a double-blind, placebo-controlled, partial three-way crossover ascending dose study the effects of THC, haloperidol and their combination were investigated in 35 healthy, male mild cannabis users, measuring Positive and Negative Syndrome Scale, Visual Analogue Scales for alertness, mood, calmness and psychedelic effects, saccadic and smooth pursuit eye measurements, electroencephalography, Body Sway, Stroop test, Visual and Verbal Learning Task, hormone levels and pharmacokinetics. Compared with placebo, THC significantly decreased smooth pursuit, Visual Analogue Scales alertness, Stroop test performance, immediate and delayed word recall and prolactin concentrations, and significantly increased positive and general Positive and Negative Syndrome Scale score, Visual Analogue Scales feeling high, Body Sway and electroencephalography alpha. Haloperidol reversed the THC-induced positive Positive and Negative Syndrome Scale increase to levels observed with haloperidol alone, but not THC-induced 'high' feelings. Compared with placebo, haloperidol significantly decreased saccadic peak velocity, smooth pursuit, Visual Analogue Scales mood and immediate and delayed word recall and significantly increased Body Sway, electroencephalography theta and prolactin levels. THC-induced increases in positive Positive and Negative Syndrome Scale but not in Visual Analogue Scales feeling high were reversed by haloperidol. This indicates that psychotic-like effects induced by THC are mediated by dopaminergic systems, but that other systems are involved in 'feeling high'. Additionally, the clear reductions of psychotic-like symptoms by a clinically relevant dose of haloperidol suggest that THC administration may be a useful pharmacological cannabinoid model for psychotic effects in healthy volunteers.

Central Nervous System (CNS) effects of talnetant, an NK-3 antagonist in development for schizophrenia, were compared to those of haloperidol and placebo. The study was randomised, double-blind, three-way crossover of talnetant 200 mg, haloperidol 3 mg or placebo. Twelve healthy males participated and EEG, saccadic and smooth pursuit eye movements, adaptive tracking, body sway, finger tapping, hormones, visual analogue scales (VAS) for alertness, mood and calmness and psychedelic effects, left/right distraction task, Tower of London and Visual and Verbal Learning Task were assessed. Haloperidol showed (difference to placebo; 95% CI; p-value) decreases in EEG alpha power (-0.87microV; -1.51/-0.22; p = 0.0110), saccadic inaccuracy (2.0%; 0.5/3.6; p = 0.0133), smooth pursuit eye movements (-7.5%; -12.0/-3.0; p = 0.0026), adaptive tracking (-3.5%; -5.4/-1.7; p = 0.0009), alertness (-6.8 mm; -11.1/-2.4; p = 0.0039), negative mood (-4.6 mm; -8.6/-0.6; p = 0.0266), the ability to control thoughts (1.2 mm; 0.2/2.3; p = 0.0214), and an increase of serum prolactin (ratio 4.1; 3.0/5.6; p < 0.0001). Talnetant showed decreased alpha power (-0.69 muV; -1.34/-0.04; p = 0.0390), improved adaptive tracking (1.9%; 0.1/3.7; p = 0.0370) and reduced calmness on VAS Bond and Lader (-4.5 mm; -8.0/-1.0; p = 0.0151). Haloperidol effects were predominantly CNS-depressant, while those of talnetant were slightly stimulatory. The results suggest that talnetant penetrates the brain, but it remains to be established whether this dose is sufficient and whether the observed effect profile is class-specific for NK3-antagonists.

In this study the effects of R213129, a selective glycine transporter 1 inhibitor, on central nervous system function were investigated in healthy males in the absence and presence of scopolamine. This was a double-blind, placebo-controlled, 4-period crossover ascending dose study evaluating the following endpoints: body sway, saccadic and smooth pursuit eye movements, pupillometry, electroencephalography, visual analogue scales for alertness, mood, calmness and psychedelic effects, adaptive tracking, finger tapping, Visual and Verbal Learning Task, Stroop test, hormone levels and pharmacokinetics. R213129 dose levels were selected based on exposure levels that blocked the GlyT1 sites >50% in preclinical experiments. Forty-three of the 45 included subjects completed the study. Scopolamine significantly affected almost every central nervous system parameter measured in this study. R213129 alone compared with placebo did not elicit pharmacodynamic changes. R213129 had some small effects on scopolamine-induced central nervous system impairments. Scopolamine-induced finger tapping impairment was further enhanced by 3 mg R213129 with 2.0 taps/10 seconds (95% CI -4.0, -0.1), electroencephalography alpha power was increased by 10 mg R213129 with respectively 12.9% (0.7, 26.6%), scopolamine-induced impairment of the Stroop test was partly reversed by 10 mg R213129 with 59 milliseconds (-110, -7). Scopolamine produced robust and consistent effects in psychomotor and cognitive function in healthy volunteers. The most logical reason for the lack of R213129 effects seems to be that the central nervous system concentrations were too low. The effects of higher doses in healthy volunteers and the clinical efficacy in patients remain to be established.