NEUROPATHIC PAIN

WHAT IS NEUROPATHIC PAIN?

Neuropathic pain describes a group of symptoms caused by damage to nerves. Central neuropathic pain may occur when nerves within the brain or spinal cord are damaged, for example spinal cord injuries, multiple sclerosis and strokes.

However, peripheral neuropathic pain is much more common and results from damage to nerves outside of the brain and spinal cord. These peripheral nerves carry sensations (feeling) to the brain and control the movement of our arms and legs. They also control the bladder and bowel.

 

WHAT CAUSES NEUROPATHIC PAIN?

The commonest causes of peripheral neuropathic pain are diabetes and shingles (herpes zoster infection). Neuropathic pain is also common in cancer patients, either as a direct result of the tumor compressing peripheral nerves or as a side effect of chemotherapy (chemotherapy-induced peripheral neuropathy).

 

HOW ARE PATIENTS WITH  NEUROPATHY PAIN AFFECTED?

The symptoms or signs of neuropathic pain depend mostly on which nerves are involved. The most common symptoms include pain, burning, tingling (pins and needles or electric / shock-like pain), loss of feeling, trouble using fingers to pick up or hold things, cold sensitivity, muscle weakness, loss of balance, tripping or stumbling while walking, difficulty swallowing, constipation and difficulty passing urine.

Patients with shingles typically notice a localized, painful, blistering rash. Nerve pain symptoms of burning, stabbing or shooting may continue once the rash has healed. When symptoms persist for more than 3 months after the rash is gone, this is called post-herpetic neuralgia (PHN; pain after shingles).

Diabetic patients with neuropathic pain typically notice symptoms in the feet and the hands. Symptoms may start in the toes, but move on to the ankles and legs. Likewise, symptoms can move up from the fingers to the hands and arms. The neuropathic pain most often affects both sides of the body in the same way. When it affects both hands and both feet, it is described as having a “glove and stocking” distribution.

 

HOW IS NEUROPATHIC PAIN TREATED?

Neuropathic pain can be very difficult to treat with only 40-60% of patients achieving partial relief.

Treatments currently used to treat neuropathic pain include local anesthetic patches (lidocaine), anti-depressant medicines (e.g., duloxetine and amitryptiline), anti-convulsants (e.g., pregabalin, gabapentin and carbamazepine) or opioids for severe, chronic pain.

 

WHAT IS THE RATIONALE FOR USING AMIKET IN NEUROPATHIC PAIN?

AmiKet contains a combination of amitriptyline and ketamine in a topical formulation.

The combination of amitriptyline and ketamine in a cream have been shown to synergistically act to relieve neuropathic pain at the local level.

 

HAS AMIKET PREVIOUSLY BEEN TESTED IN HUMANS?

AmiKet has previously been administered to 1700 patients in nine Phase I/II clinical trials. This includes three successfully completed Phase II studies in more than 600 patients with PHN, which demonstrated statistically significant pain reduction and non-inferiority to high dose gabapentin (a commonly used anti-convulsant).