A Study of Sativex® for Relief of Peripheral Neuropathic Pain Associated With Allodynia.

The purpose of this study is to evaluate the efficacy of Sativex® compared with placebo in relieving peripheral neuropathic pain associated with allodynia.

This was a six week, multicentre, double blind, randomised, placebo controlled parallel group study to evaluate the efficacy of Sativex®. Subjects with peripheral neuropathic pain characterised by allodynia, were screened to determine eligibility and entered a seven day baseline period. Subjects then returned to the centre for randomisation and dose introduction, and received either placebo or Sativex in a double blind manner for five weeks, with a follow up visit 7 to 10 days after the end of the treatment period. The primary efficacy measure was the difference in pain severity at the end of treatment, measured using a peripheral neuropathic pain 0 to 10 numerical rating scale.

Eligibility Criteria:
Inclusion Criteria:

* Willing and able to give informed consent.
* Male or female, aged 18 years or above.
* Chronic peripheral neuropathic pain of at least six months duration.
* Presence of mechanical allodynia within the territory of the affected nerve(s).
* Evidence of sensory change in the affected nerve by simple clinical tests.
* Peripheral neuropathic pain with a severity score of four or more on at least four completed NRS during the baseline week.
* Stable dose of analgesic medication for at least two weeks leading to study entry.
* Agreement, if female and of child bearing potential or if male with a partner of child bearing potential, to ensure that effective contraception was used during the study and for three months thereafter.
* Have not used cannabinoids (including cannabis, Marinol or Nabilone) for at least seven days before Visit 1 and were willing to abstain from any use of cannabinoids during the study.
* Ability (in the investigator's opinion) and willingness to comply with all study requirements.
* Agreement for the UK Home Office, their primary care physician, and their consultant if appropriate, to be notified of their participation in the study.

Exclusion Criteria:

* History of schizophrenia, other psychotic illness, severe personality disorder or other significant psychiatric disorder other than depression associated with their underlying condition.
* Concomitant severe non-neuropathic pain or the presence of cancer related neuropathic pain or neuropathic pain resulting from diabetes mellitus.
* Known history of alcohol or substance abuse.
* Severe cardiovascular disorder, such as ischaemic heart disease, arrhythmias (other than well controlled atrial fibrillation), poorly controlled hypertension or severe heart failure.
* History of epilepsy.
* If female, were pregnant or lactating, or were planning a pregnancy to occur during the course of the study.
* Significant renal or hepatic impairment.
* Elective surgery or other procedures requiring general anaesthesia scheduled to occur during the study.
* Terminal illness or were considered inappropriate for placebo medication.
* Any other significant disease or disorder which, in the opinion of the investigator, may have either put the subject at risk because of participation in the study, or may influenced the result of the study, or the subject's ability to participate in the study.
* Regular levodopa (Sinemet®, Sinement Plus®, Levodopa®, L-dopa®, Madopar®, Benserazide®) therapy within the seven days leading to study entry.
* If male, were receiving and were unwilling to stop sildenafil (Viagra®) for the duration of the study.
* Known or suspected hypersensitivity to cannabinoids or any of the excipients of the study medications.
* Known or suspected adverse reaction to cannabinoids.
* Intention to travel internationally during the study.
* Intention to donate blood during the study.
* Participation in another research study in the 12 weeks leading to study entry.
* Previous randomisation into this study