Friday, October 10, 2014

IASP 15th World Congress on Pain - Is this a meeting for palliative people?

(Please give a warm welcome to Mary Lynn McPherson, our first pharmacist writer here at Pallimed. Many of you may know her from her fantastic data filled and data driven talks on palliative medications. We're glad she is sharing her report from the 15th IASP conference! -Ed.)

The International Association for the Study of Pain (IASP) is holding its 15th World Congress of Pain meeting as I write, in Buenos Aires, Argentina. Is this a meeting for palliative care practitioners? The IASP mission is as follows: “IASP brings together scientists, clinicians, health care providers, and policy makers to stimulate and support the study of pain and to translate that knowledge into improved pain relief worldwide.” I can say after several days in attendance that they live up on this promise – there’s a little something for everyone! Today must have been neuropathic pain day because there were several outstanding presentations.

Dr. Nadine Attal presented “Neuropathic Pain: Where Are We With Our Drug Treatments and Algorithms?” She confirmed that first line options remain anticonvulsants such as pregabalin/gabapentin, and antidepressants (TCAs and SNRIs). She went on to explain however that she and her associates (IASP NeuPSIG) have completed a recent analysis of the literature, including unpublished data showing that the number of needed to treat, even with these first line options, may be higher than we realize. This analysis has been submitted for publication consideration. Dr. Attal hypothesized, and presented data to substantiate, that the future of optimal neuropathic pain treatment may be mechanism-based treatment (e.g., differentiating between burning, evoked, paroxysmal, pressing pain, etc.).

At the end of the day Drs. Dickenson, Gilron and Jensen presented “Combination Therapy for Neuropathic and Other Chronic Pain Conditions: Similarities, Differences and Therapeutic Opportunities.” Several studies have been published in recent years showing a combination of two drugs to treat neuropathic pain is superior to either drug alone, and result in less toxicity. The holy grail is when Drug A + Drug B is more efficacious than Drug A alone or Drug B alone, but no additional toxicity is seen. A good example is the study by Gilron et al. that showed nortriptyline plus gabapentin was more effective than either drug alone in treating painful diabetic neuropathy or postherpetic neuralgia. A more recent study assessed a unique titration strategy comparing duloxetine vs. pregabalin vs. the combination in the management of peripheral diabetic neuropathy that was no longer responsive to gabapentin. The results showed either drug alone and the combination had equivalent outcomes, although Dr. Gilron stated secondary outcome analyses showed a trend toward favoring the combination. Dr. Gilron concluded that that not all combinations have shown favorable outcomes, but that this line of research is intriguing and bears continued scrutiny.

But the big winner for me personally today, was the debate between Drs. Mark Ware and Andrew Rice titled “Cannabis for Neuropathic Pain: Debating the Merits of Cannabis as Medicine.” Sadly, both faculty members are true gentlemen with amazing elocution, so it wasn’t a knock-down, drag-out type of debate! Both debaters agreed that the preclinical data (animal studies) with cannabis are very promising. Dr. Ware argued that we have sufficient proof of concept data to warrant considering cannabis as a second or third line option, and the use of a vaporizer removes the concern about smoking cannabis. Dr. Rice wasn’t quite as excited about the clinical data, but he was especially concerned about the long-term effects of cannabis – namely, psychosis, which has an odds ratio of almost 3 of developing with continued use of cannabis. Dr. Rice pointed out that the above-mentioned guidelines recommended by the IASP NeuPSIG submitted for publication consideration provided a “weak recommendation against the use of cannabis in neuropathic pain on the grounds of generally negative results and potential safety concerns.” By no means down for the count, Dr. Ware’s rebuttal was crisp and decisive – cannabis is not a first line recommendation – it’s for severe, refractory neuropathic pain. He argued that this is the “art” part of practicing medicine – selecting patients for whom the benefits will hopefully exceed the burdens of therapy. Dr. Rice’s come-back was a reiteration of the long-term risks. The enthusiastic audience was STILL torn between “yea,” “nay” and “I got nothin!” My thoughts are that I agree cannabis isn’t first line, and yes, I’m worried about the psychosis and cognitive decline in a population who either already have this as a comorbidity, or are at risk to develop such. But I’m not particularly worried about the long term threat of this complication – in hospice our median length of stay is under three weeks. As with all drug therapy decisions, a benefit/burden analysis must be considered before using any medication, including cannabis.

So, yes, I think there is a little something for everyone at the IASP World Congress on Pain. And let’s not forget the obvious – they hold their meetings in really cool places! Two years ago was Milan, Italy, the current meeting in Buenos Aires, Argentina, and in two years get ready for that LONG plane ride to Yokohama, Japan!

Mary Lynn McPherson, Pharm.D., BCPS, CPE is Professor and Vice Chair of the the Department of Pharmacy Practice and Science at the University of Maryland School of Pharmacy. 

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