Study design and participants

This study was part of a multicenter, phase II, repeated crossover, randomized, double-blind, placebo-controlled, multiple-dose escalation trial of the effectiveness of THC in the treatment of the neuropsychiatric symptoms of dementia [http://www.clinicaltrials.gov, clinical trial identifier number NCT01302340]. The study was carried out at the Radboud University Medical Center, the Netherlands. Results concerning the effectiveness of THC in the management of the neuropsychiatric symptoms of dementia will be reported separately.

Figure 1 provides an overview of the study design. The study consisted of two treatment periods, A and B. Each period consisted of three treatment blocks, resulting in a total of six blocks (period A, blocks 1 to 3; period B, blocks 4 to 6). Each block lasted 2 weeks, giving a total study duration of 12 weeks. In each block, participants received oral Namisol®, a novel THC in tablet form (Klumpers et al. 2012), and matching placebo (ratio 1:1) in a double-blind crossover manner for 3 days, separated by a 4-day washout period. In period A, patients received 0.75 mg THC twice daily, and in period B, the dose was increased to 1.5 mg twice daily. Namisol® and placebo were identical in appearance and taste, and both were taken under nonfasting conditions with water at 10 a.m. and 4 p.m. Study participants stayed overnight at the study site on the three intervention days (THC and placebo) of blocks 1 and 4 for safety reasons and to facilitate blood sampling, resulting in a total of four 3-day admissions. The randomization codes were generated by an independent pharmacist, using a computer algorithm for random numbers. Sponsor, investigators, study staff, and participants were masked to assignment.

Fig. 1 Overview of the treatment period (THC and placebo were administered at random) (this is an example of random allocation of treatment) Full size image

Participants had been diagnosed with dementia type Alzheimer, vascular dementia, or mixed Alzheimer/vascular dementia, according to the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRA) (McKhann et al. 2011) or Association Internationale pour la Recherché et l’Enseignement en Neurosciences (NINCDS-AIREN) criteria (Román et al. 1993). All patients had had clinically relevant neuropsychiatric symptoms, including at least agitation and/or aggression, in the past 30 days (Neuropsychiatric Inventory score ≥10) (Cummings et al. 1994), and had an informal caregiver who looked after the participant at least once a week. Main exclusion criteria were major psychiatric disorders (e.g., major depression or suicidal ideation, psychosis, mania, or current delirium), current history of severe comorbidities, frequent falling due to orthostatic hypotension, history of current alcohol or drug abuse, and use of tricyclic antidepressants, opioids, or drugs from a predesigned list of cytochrome (CYP)2C9, CYP2C19, and CYP3A4 inhibitors. Written informed consent was obtained from participants (if they were able to consent and to sign) and their legal representatives. The study was approved by the local ethics committee and was performed according to the International Conference on Harmonization guideline for good clinical practice, the ethical principles of the Declaration of Helsinki, and relevant Dutch laws and regulations.

Safety and tolerability assessments

The safety and tolerability of THC were assessed subjectively and objectively, by evaluating the incidence and severity of adverse events, carrying out physical examinations, laboratory tests (hematology and clinical chemistry), and a 12-lead electrocardiogram, and assessing vital signs. The psychedelic effects were assessed with visual analogue scales (VAS), and body sway (postural stability) was measured using the SwayStar™ (see details below). During the study period, adverse events reported by patients and caregivers or observed clinically were recorded with regard to their time of onset, severity, duration, and causal relationship to study drugs. The causality was assessed by a research physician, blinded to treatment allocation, using a five-point scale: (1) unrelated, adverse event was clearly not related to the intervention; (2) unlikely, adverse event was doubtfully related to the intervention; (3) possible, adverse event may be related to the intervention; (4) probable, adverse event was likely related to the intervention; and (5) definite, adverse event was clearly related to the intervention. A serious adverse event was defined as any event that was fatal or life-threatening, that required (prolonged) hospitalization, or that resulted in persistent or significant disability or incapacity. All adverse events were coded using the Medical Dictionary for Regulatory Activities.

Pharmacodynamic effects

The scores for psychedelic effects, body sway, and vital signs were used to evaluate the pharmacodynamic effects of THC.

1. Psychedelic effects: The Bowdle VAS for psychedelic effects was used to evaluate feeling high, internal perception (inner feelings that do not correspond with reality, including mistrustful feelings), and external perception (misperception of an external stimulus or change in awareness of surroundings) (Bowdle et al. 1998; Zuurman et al. 2008). Subjects were asked to score their perceptions on a 100-mm horizontal line, with “0” indicating no effect and “100” indicating extreme effect. The VAS was assessed 1 and 3 h after dosing on day 1 of weeks 1, 2, 7, and 8, in patients who were able to understand the instructions and perform the task. A recent study showed that individuals with dementia can use the VAS in a similar way to those without dementia (Arons et al. 2013). 2. Body sway: Body sway was assessed within 2 h of dosing on the second day of admission of weeks 1, 2, 7, and 8. Body sway was measured (30 s eyes open and 30 s eyes closed) with the SwayStar™, a wireless device attached to the trunk (http://www.b2i.info/web/index.htm). 3. Vital signs: Systolic and diastolic blood pressure and heart rate were measured on day 1 of weeks 1, 2, 7, and 8, before and at 15, 30, 45 min, and 1, 2, 3, and 4 h after the first dose.

Blood sampling and laboratory analysis

Venous blood samples were collected during hospital admission before and at 11, 30, 45 min, and 1, 1.5, 2, 3, 4, and 6 h after the first dose, and before and at 11, 30, 45 min, and 1, 1.5, 2, 3, 4, 6, and 18 h after the second dose (in total covering a 24-h period). Plasma was separated by centrifugation (2000 × g, 4 °C, 10 min) and stored at −80 °C until analysis. After unblinding, blood samples collected in the THC treatment period were analyzed at the Analytisch Biochemisch Laboratorium b.v. (Assen, the Netherlands), using liquid chromatography with tandem-mass spectrometer detection. The lower limit of quantification was 0.1 ng/mL for THC and its active metabolite 11-OH-THC. The analysis was performed using a validated assay according to good laboratory practice standards (Guidance for Industry: Bioanalytical Method Validation 2001; Viswanathan et al. 2007).

Pharmacokinetic analysis

Noncompartmental analysis was performed using Phoenix WinNonlin software version 6.3 (Certara, L.P./Pharsight Ltd) to determine the pharmacokinetics of THC and 11-OH-THC. The following pharmacokinetic parameters were calculated for the 24-h period: terminal half-life (t 1/2 ), area under the curve (AUC) from 0 to 24 h (AUC 0–24 h ), and apparent clearance (CL/F, being the dose/AUC 0–24 h ). The following parameters were calculated for the two curves (curve 1, 0–6 h after the first THC dose; curve 2, 6–24 h after the second dose) separately: the maximum plasma concentration (C max ), the time to reach C max (T max ), AUC from 0 to 6 h (AUC 0–6 h ), and AUC from 6 to 24 h (AUC 6–24 h ), using the linear-up log-down trapezoidal rule. Concentration-time graphs were plotted for the two doses. Geometric means plus 95 % confidence intervals were calculated for each pharmacokinetic parameter for each dose. The coefficients of variation (CV%) of the geometric means were calculated to describe the interindividual variability in pharmacokinetic parameters. The geometric mean ratio (GMR) plus 90 % confidence intervals of AUC 0–24 h , CL/F, and t 1/2 of the 1.5-mg dose versus the 0.75-mg dose were also calculated.

Statistical analysis

This study is descriptive and explorative, and therefore, no sample size calculation was performed. Descriptive statistics were used to describe the study population. Continuous data are expressed as means ± standard deviation (±SD), and categorical data are expressed as frequencies and percentages. The compliance to study medication was calculated for the whole study sample. Differences in adverse event rates between THC and placebo were compared by Wilcoxon signed ranks test. The VAS scores were clustered and log-transformed, and the scores are expressed as units, as described previously (Zuurman et al. 2008; Klumpers et al. 2012). The 90 % range of pitch velocity (anterior–posterior movements) scores of the SwayStar™ was used to analyze body sway. Scores are given in degrees per second. The VAS, body sway, and vital signs scores were analyzed in relation to the THC dose, using linear mixed models with participants as a random effect. Statistical analyses were performed using SAS™ software, version 9.2 (SAS Institute, Inc., Cary, NC, USA).