Methotrexate - some thoughts

Today I wanted to write about a specific. It hasn't been in the news recently but caught my interest because it did something unexpected.

Methotrexate (shown at left) is a very interesting compound. Its history began with FDA approval in 1953 for oncology use.

It gets the job done by inhibiting folic acid breakdown.

Folic Acid or Folate is water soluble vitamin B9 (pictured right). [Note the similar structural elements of methotrexate and Folic Acid] Folic Acid is broken down to form tetrahydrofolate, a metabolite necessary for DNA synthesis, by the enzyme dihydrofolate reductase. Due to their similar structure, methotrexate can bind dihydrofolate reductase, block folic acid breakdown, and slow DNA synthesis. This is preferentially damaging cancer and immune system cells as they grow particularly fast and rely on DNA synthesis for their growth.

Methotrexate therefore has been used for chemotherapy (high dose) and as a treatment for inflammation associated with the autoimmune response (low dose).

A patient mentioned that Methotrexate relieved her symptoms of Fibromyalgia (a disease defined by chronic pain, abnormal pain processing, fatigue, brain fog, etc...). Why did this happen?

The etiology of fibromyalgia is still unknown. However, methotrexate has been used for a similar disease. Behçet's syndrome is characterized by generalized inflammation that causes ulcers, arthritus, and cardiac problems to a name some symptomes. Behçet's syndrome, like Fibromyalgia, is not well understood. The two diseases have overlapping symptoms of pain, fatigue and cognitive difficulties.

Something still doesn't add up. Methotrexate decreases inflammation and relieves symptoms associated with Behçet's syndrome and yet also pain associated with Fibromyalgia?.

Pain is caused by the activation of a nociceptor (pain receptor) by a mechanical or chemical stimuli. The message is passed by the nervous system through the spinal cord to the brain which responds by understanding the impulse as pain. Inflammation, among a variety of things, is known to cause the release of algesic substances which activate the nociceptors. The pictures comes full circle.

The overlap is there. A compound used for anti inflammatory disease helps with pain in disease states that are associated with inflammation. The difficulty is of course to really know whats happening. The woman who mentioned pain improvement was taking the methotrexate for retinal inflammation and happened to have fibromyalgia.

How do we make this connection faster? Is it smart to push for a clinical trial for methotrexate as a pain treatment when resources in the Fibromyalgia community are limited? Yet, it is these random observations that seem important. I guess thats why these are just some thoughts.

A joke at every end:

A blind man walks into a pharmacy with his guide dog.
He lifts his dog and starts spinning the dog by its leash.
A store employee runs up to the man and asks "hey, what are you doing?"
The blind man replies "just looking around."

Memory and Anesthesia

Proc Natl Acad Sci U S A. 2008 February 5; 105(5): 1722–1727.

Sevoflurane (shown to the right) is used in the induction or maintenance of general anesthesia. It boils at 58 degrees Celsius and is administered through an anesthetic vaporizer with a mixture of nitrous oxide and oxygen. The mechanism of action for sevoflurane is yet unknown. It is one molecule in a class of fluorinated methyl ethyl ethers and fluorinated methyl isopropyl ethers that are currently being used for anesthesia. These anesthesia compounds must have at max 4 carbons as their volatility (decreased with increased molecular weight) is necessary for action (Anesthesiology. 2008 Mar;108(3):531-3.) Interestingly, soda lime is used in anesthesiology to absorb exhaled carbon dioxide (reaction shown below) and the anesthetic agents need to be monitored for side reactions with soda lime.

1. CO2 + H2O --> H2CO3
2. H2CO3 + 2 NaOH (or KOH) --> Na2CO3 (or K2CO3) + 2 H2O + Energy
3. Na2CO3 (or K2CO3) + Ca(OH)2 --> CaCO3 + 2 NaOH (or KOH) (source)

Here are the components of soda lime: H2O (water), Ca(OH)2 (third reaction), NaOH (second reaciton- recycled in reaction), KOH (second reaction - recycle). Wet soda lime must be used - to force reaction 2. Otherwise Sevoflurane reacts with dry soda lime to form CF2=C(CF3)OCH2F. It seems this occurs through an elimination reaction with the hydrogen from the carbon neighbored by oxygen and the two fluorinated carbons. A fluorine is a good leaving group and what could abstract this hydrogen? Not H2O, Ca(OH)2 probably could and would form water. Perhaps, extra water would limit this side reaction (equilibrium). Well this is a side track.

I wanted to talk about memory, which is thought to be made through a neurobiological mechanism involving the amygdala. What was really cool about the study mentioned above is that they used no more than 0.25% sevoflurane doses in the study. To make this story short, subjects remembered less traumatic images with this low dose of anesthesia as compared to placebo. The article shows that the anesthesia lowered the metabolic rate of the thalamus (not amygdala) but the suppression was in areas of the brain that "interact with the amygdala and are known to play a role in mediating arousal and controlling the level of consciousness during anesthesia."

Furthermore, two doses 0.2% and 0.25% decreased memory of emotional slides while the o.10% enhanced this recollection. Further work is definitely going to be done to figure out whats going on. This has been mentioned as having the potential to relieve post traumatic stress disorder by breaking the connection of a certain image or thought with the amygdala. There is definitely more work to be done as the implications are very exciting!

A joke at every end:

A panda walks into a bar and orders spaghetti.
After the panda finishes he takes out a bow and arrow and shoots the bartender in the heart.
Next night, the panda walks into the same bar and orders lobster.
After the panda finishes he takes out a gun and pops the new bartender.
The next night, the panda walks in and orders pork chops.
The new bartender says "woh, I am not gonna serve you, you've injured the two previous bartenders, what's your problem panda."
"But I am a panda" says the panda.
"Hey, since when do pandas cause so much trouble! No panda I know" replies the bartender.
"Oh yea, look it up," says the panda "in that dictionary behind you"
The bartender pulls down the dictionary, opens to Panda and reads aloud.
"Panda: eats shoots and leaves."

Heparin

February 28th: Baxter International Inc. requests a voluntary recall of its anticoagulant medication heparin. This molecule is derived from animal (commonly pork) organ tissue. As seen on the right, heparin is a disaccharride with varying sugar constituents. The most common disaccharide combination (left) contains an amide and a sulfate group, both of which are de-ptrotected and attract a positive sodium ion. It is sodium heparin that is injected as medication to thin the blood of patients for a variety of indications.

So what happened? Well, over 700 people had adverse reactions after receiving heparin for dialysis or venous thromboembolism (blood clot) to name two indications.

Baxter International Inc. sells the drug and has something like 50% of America's market share. The company receives the main active ingredient from a company called Scientific Protein Laboratories. SPL, for short, is based out of Wisconsin but relies on a factory in China for extraction of the api (active pharmaceutical ingredient) from pig organs. To make a long story short, China's State FDA did not inspect this particular factory because it only produces exports. USA's FDA accidently inspected the wrong factory due to a mix up in database input and the fact that the other factory had a like sounding name(C&EN, Feb 25, 2008, Vol 86, #08, p.8).

More recently, the contaminant has been identified as Chondroitin Sulfate (right - C&EN, Mar 19, 2008). The molecule is commonly found in cartilage of animals (like pigs) and has been used by the alternative medicine community to treat arthritis. In this case, the Chondroitin Sulfate, had more sulfate groups than are commonly found in nature and is considered a purposely introduced contaminant. The over sulfated Chondroitin Sulfate is cheap and because of its structure it mimics heparin in regulatory and potency tests.

Chinese companies, that rely on SPL for this API, have also recalled the drug. Other heparin producers are being encouraged to increase output (their API producers have been approved by the FDA).

This is a growing concern. The trend of the chemical industry has been to expand its laboratory work to international ground (cheaper labor, more supportive government). The burden on the FDA to ensure the authenticity of imported drugs grows. This will be an ongoing challenge and a very important one.

A joke at every end:

What did the bra say to the hat?
"You go on ahead, I'll give those two a lift."