Much to learn about med­i­cal mar­i­juana

The Guardian (Charlottetown) - - OPINION - BY DES COLOHAN Desmond Colohan, MD, re­cently re­tired from the clin­i­cal prac­tice of pain medicine.

A re­cent front-page head­line in the Guardian was sure to get the at­ten­tion of the many Is­lan­ders suf­fer­ing from acute and chronic pain.

It re­ported on a con­fer­ence on med­i­cal mar­i­juana held in Char­lot­te­town. The key­note speaker de­liv­ered a sin­cere endorsement of cannabis in help­ing him man­age his chronic back pain and symp­toms of mul­ti­ple scle­ro­sis. He rec­om­mended that physi­cians use cannabis as a first line drug to treat pain.

He im­plied that many physi­cians are ig­no­rant of the ben­e­fits of cannabis and need to be en­cour­aged to “get with the pro­gram.”

As a spe­cial­ist in pain medicine, I have had con­sid­er­able ex­pe­ri­ence work­ing with pa­tients us­ing med­i­cal mar­i­juana, and, with due re­spect, would cau­tion that mar­i­juana is not “safer than wa­ter,” nor is it as es­sen­tial to life.

Physi­cians are hes­i­tant to em­brace not yet proven ther­a­pies, par­tic­u­larly when the pre­pon­der­ance of sup­port comes from tes­ti­mo­ni­als and po­lit­i­cal ac­tivism, and not through care­fully de­signed clin­i­cal test­ing.

Opin­ions to the con­trary, we do in­deed know quite a bit about cannabis, its botany, its ef­fects on hu­mans, its clin­i­cal util­ity and many of its risks and ben­e­fits.

Un­for­tu­nately, much of our knowl­edge comes from an­i­mal re­search and not a whole lot from clin­i­cal test­ing on hu­mans.

Ac­cord­ing to our ex­perts, here's some of what we know.

Clin­i­cal stud­ies sup­port­ing the safety and ef­fi­cacy of smoked cannabis for ther­a­peu­tic pur­poses are lim­ited, but slowly in­creas­ing in num­ber. There are no clin­i­cal stud­ies on the use of cannabis ed­i­bles (e.g. cook­ies, baked goods) or top­i­cals for ther­a­peu­tic pur­poses. It has been re­peat­edly ob­served that the psy­chotropic side ef­fects of cannabi­noids limit their util­ity.

Cannabis smoke con­tains many com­pounds not found in ei­ther ex­tracts or vapour, in­clud­ing a num­ber which are known or sus­pected car­cino­gens or mu­ta­gens. More­over, com­par­isons be­tween cannabis smoke and to­bacco smoke have shown that the for­mer con­tains many of the same car­cino­genic chem­i­cals found in to­bacco smoke.

The body’s en­do­cannabi­noid sys­tem plays an im­por­tant role in the mod­u­la­tion of pain states. Re­search in­volv­ing pa­tients suf­fer­ing from pain sug­gests that cannabi­noids may be most ef­fec­tive for chronic, pri­mar­ily neu­ro­pathic pain.

There is ev­i­dence that cannabis de­pen­dence (phys­i­cal and psy­cho­log­i­cal) oc­curs, es­pe­cially with chronic heavy use. The ad­dic­tion po­ten­tial for cannabis has been es­ti­mated at about nine per cent, com­pared to nico­tine at 32 per cent or heroin at 23 per cent.

Cannabis should not be used by any per­son un­der the age of 18. The ad­verse ef­fects of cannabis on men­tal health are greater dur­ing ado­les­cence than in adult­hood. The risk of an acute psy­chotic break by age 26 is 4.5 times higher in reg­u­lar cannabis smok­ers who start at age 15. It is 1.6 times higher if cannabis smok­ing doesn’t start un­til age 18. The risk of de­vel­op­ing schizophre­nia dou­bles in reg­u­lar cannabis users, par­tic­u­larly those us­ing high-po­tency sin­semilla [skunk] who start in their early teens. Chronic cannabis use may have neg­a­tive ef­fects on mem­ory.

The rou­tine use of cannabi­noids to treat pri­mary anx­i­ety or de­pres­sion should be viewed with cau­tion, and es­pe­cially dis­cour­aged in pa­tients with a history of psy­chotic dis­or­ders.

Cannabis should be used cau­tiously in pa­tients with a history of sub­stance abuse be­cause such in­di­vid­u­als may be more prone to abus­ing cannabis.

Cannabis should be used with cau­tion in pa­tients re­ceiv­ing con­comi­tant ther­apy with seda­tive-hyp­notics or other psy­choac­tive drugs be­cause of the in­creased risk of over­dose or ad­dic­tion due to ad­di­tive or syn­er­gis­tic CNS de­pres­sant or psy­choac­tive ef­fects.

Cannabis is not rec­om­mended for women of child­bear­ing age not on a re­li­able con­tra­cep­tive, as well as those plan­ning preg­nancy, who are preg­nant or women who are breast­feed­ing. Men, es­pe­cially those on the bor­der­line of in­fer­til­ity and in­tend­ing to start a fam­ily, are cau­tioned against us­ing cannabis since ex­po­sure could po­ten­tially re­duce the suc­cess rates of in­tended preg­nan­cies.

Pa­tients us­ing cannabis should be warned not to drive or to per­form haz­ardous tasks be­cause im­pair­ment of men­tal alert­ness and phys­i­cal co­or­di­na­tion may de­crease their abil­ity to per­form such tasks.

The es­ti­mated hu­man lethal dose of in­tra­venous tetrahy­dro­cannabi­nol [THC] is 30 mg/kg, although there have been no doc­u­mented deaths ex­clu­sively at­trib­ut­able to cannabis over­dose.

In my ex­pe­ri­ence, the ther­a­peu­tic value of cannabis in man­ag­ing chronic pain is lim­ited by its ad­verse ef­fects.

We still have a lot to learn about the ap­pro­pri­ate clin­i­cal use of ' med­i­cal mar­i­juana' and should not be in a hurry to jump on this band­wagon.

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