Sunday, 8 January 2012

Valganciclovir

From the previous post of Dr. Montoya's lecture about trialling Valganciclovir as an M.E. medication/treatment, I looked up more particulars about this drug. Most of the following information comes from Wikipedia.


It has been proposed that valganciclovir could be used in the treatment of chronic fatigue syndrome. Following some reported success in 9 out of 12 patients at Stanford University in California, a follow-up double-blind, controlled study of 30 patients was completed, and although data has not yet been released, according to the Virus Induced CNS Dysfunction Association, "the data Dr. Montoya presented at the 2008 International Conference on HHV-6&7 indicated that patients on Valcyte experienced significant cognitive improvement.", especially for those with elevated antibody levels to HHV-6 and EBV (VCA and EA).


Valganciclovir hydrochloride (Valcyte, manufactured by Hoffmann–La Roche (Roche). Also Cymeval, Valcyt, Valixa, Darilin, Rovalcyte, Valcyte, Patheon, Syntex) is an antiviral medication used to treat cytomegalovirus, CMV (essentially a herpes virus, (specifically CMV belongs to the Betaherpesvirinae subfamily, which also includes the genera Muromegalovirus and Roseolovirus (HHV-6 and HHV-7).) of which there are multiple types, from shingles, to Epstein Barr - again, don't forget the parallel to M.E. in how herpes viruses can lie dormant in a person, becoming cyclically 'active' between very long periods of dormancy) infections. It is a prodrug for ganciclovir, ie, it quickly converts to ganciclovir in the body. Valganciclovir is administered orally.


Side effects (don't sound good...)
Blood: neutropenia, anemia, low platelets. Myelosuppression is one of the main side effects that may limit prolonged use of valganciclovir.
Gastrointestinal: diarrhea, nausea, vomiting, abdominal pain
Central nervous system: fever, headache, insomnia, paresthesia, and peripheral neuropathy
Ocular: retinal detachment


A generic version of the drug is manufactured by Japanese-owned Indian company Daiichi-Ranbaxy.


In short, Valganciclovir is a synthetic drug. In my own opinion, synthetic drug intervention should only be used as a last resort when other options are limited. There is simply not enough evidence of how effective or harmful this drug could be to a user for me to feel reassured enough that it could work for me. Remember that even the subjects in Dr. Montoya's study had to be taken off Valganciclovir at some point because it's long-term use was questionable.


In looking up the efficacy of Valganciclovir, I came across the term BIOAVAILABILITY. This is an area that I want to look in to more detail over the coming year as I start to find ways to improve my diet in relation to improving the uptake of nutrients by my body in order to try and strengthen the immune system and optimize energy transfer.


Essentially, bioavailability means how much of the substance is actually absorbed by the body rather than just passing through. Intravenous administration has maximal bioavailability, but oral intake is less hard to measure because of so many variables from person to person. It can never be 100%. Some of these variables could hold keys to where nutritional gain could be improved. Things such as mixed ingredients, fats vs. water, could inhibit adsoption, for example, so maybe worth looking at food combinations or foods that are less soluble.


Some variables as listed on Wikipedia are:
Physical properties of the drug (hydrophobicity, pKa, solubility)
The drug formulation (immediate release, excipients used, manufacturing methods, modified release – delayed release, extended release, sustained release, etc.)
Whether the formulation is administered in a fed or fasted state
Gastric emptying rate
Circadian differences
Interactions with other drugs/foods:
Interactions with other drugs (e.g., antacids, alcohol, nicotine)
Interactions with other foods (e.g., grapefruit juice, pomello, cranberry juice, brassica vegetables)
Transporters: Substrate of efflux transporters (e.g. P-glycoprotein)
Health of the GI tract
Enzyme induction/inhibition by other drugs/foods:
Enzyme induction (increased rate of metabolism), e.g., Phenytoin induces CYP1A2, CYP2C9, CYP2C19, and CYP3A4
Enzyme inhibition (decreased rate of metabolism), e.g., grapefruit juice inhibits CYP3A → higher nifedipine concentrations
Individual variation in metabolic differences
Age: In general, drugs are metabolized more slowly in fetal, neonatal, and geriatric populations
Phenotypic differences, enterohepatic circulation, diet, gender
Disease state E.g., hepatic insufficiency, poor renal function

No comments:

Post a Comment