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The role of Ketamine in combating pain in people with allodynia

  • Writer: Randy Justus
    Randy Justus
  • May 4
  • 5 min read

Updated: May 4



This information is for informational purposes only and does not replace professional medical advice. Always consult a licensed healthcare provider for concerns about your health.


Summary: After experiencing allodynia “skin pain and sensitivity” for myself and finding that there seems to be no consensus on treatments. I decided to find all the research I could to alleviate my pain.


Common treatments include oral medications like anticonvulsants and antidepressants, topical therapies containing lidocaine or capsaicin, and physical therapy to desensitize the affected area. Psychological interventions like cognitive behavioral therapy (CBT) may also be recommended to help manage pain perception and cope with the emotional impact of the condition.


I was prescribed opioids and topical preparations. The opioids had no effect and the topicals lasted only about an hour or two at most and didn’t relieve all my pain. I was already taking oral ketamine for depression and anxiety. I found 150mg to 200mg per day would alleviate the pain and was tolerated well in myself. This falls within the dosing protocols in the limited research that there is.


What I found after speaking with multiple medical professionals and pharmacists that no one is following a standard protocol. Most Ketamine Clinics are focused on the mental side of Ketamine and completely ignoring their pain patients.

The following describes what allodynia is and highlights the limited research available in treating it with ketamine both orally and by route of intravenous infusion.


What is allodynia? Allodynia is a condition where normally innocuous stimuli, like light touch, cause pain. It's essentially a heightened sensitivity to touch, where the skin becomes overly sensitive, and even gentle contact can be painful. 


1.      The first study we’ll look at is the Beneficial effects of ketamine in a chronic pain state with allodynia, possibly due to central sensitization https://pubmed.ncbi.nlm.nih.gov/7784107/

This was a case of one patient, a previously healthy 17-year-old girl in and around a persistently suppurating appendectomy wound. There was no spontaneous pain but pronounced allodynia in the wound and in the surrounding skin.

Since the pain responded poorly to opioids and ketamine has been reported to reduce allodynia, it was administered in a sub-dissociative bolus dose during wound dressing. The wound was essentially unchanged after treatment for 3 months, but the allodynia and sensory aberrations had decreased significantly. We interpret these results as a de-sensitizing effect in the long term of repeated NMDA-receptor blockade by ketamine in a chronic pain state, with indications of central sensitization, partially maintained by sympathetic activity.


2.      Use of oral ketamine in chronic pain management https://pubmed.ncbi.nlm.nih.gov/19879174/

The analgesic effect of ketamine is primarily based on the antagonism of the N-methyl-d-aspartate (NMDA) receptor. Activation of NMDA receptors may play a crucial role in the pathogenesis of chronic pain. A recommended starting dosage in ketamine-naive patients is 0.5 mg/kg racemic ketamine or 0.25 mg/kg S-ketamine as a single oral dose. The dosage is increased by the same amount if required. For a continuous analgesic effect it is usually given 3-4 times daily.


3.      An Unusual Case of Chronic Neuropathic Pain Responds to an Optimum Frequency of Intravenous Ketamine Infusions https://www.jpsmjournal.com/article/S0885-3924(01)00253-6/fulltext

The effective treatment of patients suffering from a variety of difficult pain syndromes, including phantom pain and other neuropathic pains, remains a clinical challenge. Neuropathic pain has been shown to respond to drugs that block the N-methyl-D-aspartate (NMDA) receptor, such as ketamine.

Neuropathic pain syndromes can include the clinical components of allodynia, hyperalgesia, and hyperpathia. Evidence from the basic sciences suggests that hyperalgesia and allodynia following peripheral nerve damage is due not only to an increased sensitivity of peripheral nociceptors in the affected area, but also to N-methyl-D-aspartate (NMDA) receptor mediated changes in synaptic excitability in the dorsal horn of the spinal cord. 

Phantom limb pain, and other types of neuropathic pain, have been shown to respond to drugs which block the NMDA receptor, such as ketamine.

A trial of the NMDA receptor antagonist ketamine was commenced. A continuous subcutaneous infusion was started at a dose of 200mg/24 hours. The pain responded very well to the ketamine infusion, but the infusion had to be discontinued after one week because of the problems with sterile abscesses at the syringe driver sites. 


Three adult trials administered ketamine orally, and one case report of oral ketamine in children was included. The authors found an oral starting dose of 0.75 to 1.5 mg/kg/day to be typical amongst adult patients. Most studies were short-term, but one study continued therapy for up to 60 days. The authors considered oral ketamine to be a potential option for treatment-refractory cancer pain despite the limited data.


5.      Ketamine for chronic pain: risks and benefits https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bcp.12094

The anesthetic ketamine is used to treat various chronic pain syndromes, especially those that have a neuropathic component. Low dose ketamine produces strong analgesia in neuropathic pain states, presumably by inhibition of the N-methyl-D-aspartate receptor although other mechanisms are possibly involved, including enhancement of descending inhibition and anti-inflammatory effects at central sites.

There is evidence that long term treatment of chronic pain (particularly in pain with a neuropathic component) with ketamine will cause prolonged pain relief.


Among these new guidelines for managing chronic pain with ketamine infusions are a bolus of up to 0.35 mg/kg, an infusion of 0.5 to 2 mg/kg per hour and a dose–response relationship. The journal Regional Anesthesia and Pain Medicine also published the consensus guidelines for ketamine and acute pain simultaneously.


The American Society of Regional Anesthesia and Pain Medicine (ASRA) published consensus guidelines on intravenous ketamine for acute and chronic pain in 2018.10,11 These guidelines include brief recommendations for oral ketamine. For chronic pain, ASRA concluded that there was low-level evidence to support the use of oral ketamine at a dosage of 150 mg/day or 0.5 mg/kg every 6 hours.10 Recommendations for acute pain concluded that the evidence for oral ketamine in acute pain was limited, but evidence indicates it may provide short-term benefit. The evidence was also considered low level.


8.      Colorado Hospital Association Oral Ketamine Tip Sheet https://cha.com/wp-content/uploads/2019/09/M3_Oral-Ketamine-Tip-Sheet.pdf

Starting dose po ketamine 25-50 mg TID with meals, Titration: Can increase by 25-50 mg per dose every one to three days based on efficacy and adverse effects.


This information is for informational purposes only and does not replace professional medical advice. Always consult a licensed healthcare provider for concerns about your health.


Conclusion: I found that a 2-hour ketamine infusion of a dose at .5mg/kg to 1mg/kg of body weight relieved the pain and sensitivity completely for 2 weeks. Oral ketamine of 150mg to 200mg daily suppressed the symptoms between infusions. After a couple of weeks, I was able to drop to 75mg per day to achieve the same effects.


There are some concerns about the potential for bladder, kidney and liver toxicity and problems over an extended period. The problem is there seems to be no consensus of dosage and what that amount of time is. I’ve found claims that more than 400mg per day over a 2-to-4-year period causes the problems, but I’ve also found that it happens with over 1000mg per day. The only good study I found was on one patient that this happened, but she was on a cocktail of other medications that had the potential to interact with each other to cause the same problems. It has been found that recreational users are more likely to experience adverse effects.


Ketamine has been a life-changing medication for me not only from a pain alleviating perspective, but as a former law enforcement officer it has led to me finding an effective treatment (along with traditional therapy) for my depression, ptsd and anger issues.


For more information contact me at info@randyjustus.com

 
 
 

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