peroxynitrate and antioxidants

[Bucklecroft Rudy]

Eradicate opiate tolerance

peroxynitrate is an oxidant
Vit C is an antioxidant
Peroxy. raises opiate tolerance
Vit C reduces tolerance

Sound logical?

 

[Epsilon Alpha]

While your op isn't really ADD material (at least post the studies bud), it does feed into a interesting link between some aspects of tolerance and the NO pathway. Peroxynitrate is created as a by product of NO synthesis, which has a ton of links to tolerance.

Also, its one of the less appreciated parts of the whole amphetamine tolerance thing I posted a while back.

 

[Bucklecroft Rudy]

http://img.exigo.com/public/1485/we...oxynitrite-Mediated Oxidation of Dopamine.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714174/

Using an animal model, Salvemini and her colleagues found that that a substance called peroxynitrite plays a critical role in the development of morphine tolerance. Repeated doses of morphine cause peroxynitrite to develop in the spinal cord, which in turn causes inflammation and damage to proteins and DNA in that area.

The researchers found they could prevent morphine tolerance from occurring by therapeutically manipulating peroxynitrite - in other words, prevent it from working. They did that by either causing the substance to decompose once it had developed or by blocking it from forming in the first place.

"We believe our findings can be used by researchers to develop therapies that will allow patients to take morphine without becoming tolerant of its benefits," said Salvemini. "For instance, when morphine is administered, another drug could be given simultaneously that prevents peroxynitrite from working and thus causing tolerance to develop.

"The benefit of this research is potentially quite large in terms of maintaining the pain-relieving effect of opiates such as morphine during prolong use while also reducing their side effects."

Article: Therapeutic manipulation of peroxynitrite attenuates the development of opiate-induced antinociceptive tolerance in mice, Journal Of Clinical Investigation, November, 2007.

The study was supported by grants from COFIN 2005 (Italy), IRCS Centro Neurolesi (Italy), Saint Louis University and the University of Florence (Italy).

Hope this raises the tone lol

 

[Bucklecroft Rudy]

opiate tolerance is a result of several pathways but it can be reduced to negligible levels

Cholecystokinin
Peroxynitrite
G protein coupling
No desensitization or endocytosis of receptors
NMDA
Dopamine/Serotonin depletion

http://www.opioids.com/morphine/magnesium.html
http://www.opioids.com/tolerance/mechanism.html
http://www.opioids.com/tolerance/agonistantagonist.html
http://www.opioids.com/tolerance/molecular.html
http://www.opioids.com/tolerance/paincontrol.html

All these have remedies and each onne interestingly lowers tolerance by 25-90% esp proglumetacin/naltrexone. Bupe holidays also seem to lower tolerance 2 week break on bupe (taper)+ ULD Nltx to pare receptors is equal to a long break for me

At the current time, the cellular and molecular mechanisms of tolerance are under intense scrutiny. With our increased understanding of the mechanisms of opiate receptor activation, both adenylate cyclase inhibition and changes in ion-channel activities may play a role in tolerance (17,29,38,47,49,53,54). Opioid receptors use G protein (guanine nucleotide regulatory protein) as a coupling component in their signal transduction mechanism. G proteins ``couple'' receptors to effector proteins and regulate both effector activity as well as the receptor affinity for hormonal ligands. There are at least five families of G proteins and each G protein has three subunits that undergo complex interaction with each other to modulate receptor and effector activities (43). It is currently believed that the inhibitory G protein (Gi) is associated with inhibition of adenylate cyclase activity by delta opioids. Kp channel activation by mu and delta receptors is probably mediated by Gi or Go. Kappa receptor activation inhibits voltage-sensitive calcium channels and, via Go, calcium currents are inhibited by delta receptor activation. Su et al. (50) described these molecular mechanisms and proposed a working model for in vivo opioid tolerance. They suggest that there are potentially two mechanisms of opioid tolerance=mopioid receptor down[chreg[chulation and uncoupling of receptors from G proteins. Morphine does not produce downregulation but does induce uncoupling of receptors. It remains unclear why nonpeptide opioids like morphine are not able to induce receptor downregulation.

In studies to further address the mechanism of tolerance, several investigators addressing the mechanisms of these neuroadaptive behaviors have focused on the concept that tolerance and physical dependence are experience-dependent, reversible changes and can be considered hallmark examples of behavioral plasticity (53,54). N -methyl-[smd[nm-aspartate (NMDA) receptors are a subclass of excitatory amino acid receptors that, once activated, produce calcium influx in neurons. From numerous studies, it has now been demonstrated that NMDA receptor antagonists, including the noncompetitive antagonist, MK801, and the nonselective excitatory amino acid antagonist, kynurenic acid, inhibit tolerance to the analgesic effects of repeated morphine administration without affecting either pain responsiveness on its own or the acute analgesic actions of morphine (33,54). Further studies have now demonstrated that NMDA antagonists not only prevent tolerance development but also can reverse it once it has occurred.

Trujillo and Akil (53) proposed the following series of events that occur with chronic opioid administration as a means to define a mechanistic hypothesis for tolerance. They suggest that, following the exogenous administration of an opiate, opiate receptors are affectively coupled to G proteins and the acute actions of the drugs are manifest.

With chronic opioid receptor occupation, a functional decoupling of opioid receptors from G proteins occurs and the acute effects of the drugs decrease. Tolerance develops and higher doses of opiate are necessary to trigger the second messenger response to produce physiologic and behavioral effects. With chronic opioid exposure, there is a decrease in endogenous opioid biosynthesis that may have no obvious consequences but is made evident when the exogenous drug is terminated. A rebound hyperexcitability of opioid responsive neurons occurs resulting from physiologic changes within opioid-responsive neurons themselves, from the decreased activity of endogenous opioid neurons, or from excessive activity of excitatory inputs. The increased firing of these neurons is what is described as the syndrome of opiate abstinence. Eventually, in the absence of any exogenous opioid drug, opioidreceptor coupling to the G protein begins to recur, as does recovery of endogenous opioid biosynthesis. In short, opioid tolerance and dependence may be related both to a functional decoupling of opioid receptors from second-messenger events and a decrease in the availability of endogenous opioid peptides.

One question that has arisen is: What is the mechanism by which an NMDA receptor antagonist mediates this impact on tolerance? The question is whether the receptors act directly at endogenous opioid synapses or at a site or sites distal to these. One hypothesis is that the NMDA receptor-mediated increase in intracellular calcium may be involved in the changes in receptor coupling, opioid peptide biosynthesis, or both (17). If this is correct, then NMDA receptor antagonists would inhibit opiate tolerance and physical dependence by directly interfering with the cellular and molecular changes thought to be involved in these phenomena.

Further evidence to support this hypothesis comes from studies with nitric oxide (26). Pasternak et al. implicated nitric oxide in the mechanisms of mu receptor tolerance and dependence. They demonstrated that the nitric oxide synthase inhibitor (NO-arginine) (N[cf11]G -itro-[sml[nm-arginine) blocks the development of tolerance to morphine in a dose-dependent manner. The actions are restricted to the mu opiate morphine. This agent did not prevent tolerance to kappa or kappa agents. These data support the observation that the development of tolerance to mu and kappa drugs involves pharmacologically distinct mechanisms of action. Moreover, it suggests that this selective effect of nitric oxide synthase inhibitors to interfere with tolerance may involve a parallel noninteracting system with the NMDA antagonists. The authors suggest that it is unlikely that the nitric oxide synthase inhibitors are interfering with learning processes because of their selective effect on tolerance to mu rather than to kappa analgesics. Of particular interest is the fact that nitric oxide synthase is an enzyme identified within specific regions of the brain known to contain opioid receptors and to be important in the production of analgesia. It does not appear at the present time that nitric oxide synthase corresponds to specific sites of mu receptors or other known opioid receptor subtypes and may therefore not play a widespread role in opioid action. However, the ability of both nitric oxide synthase inhibitors and an NMDA antagonist to reduce tolerance provides a great advantage in the use of opioid analgesics. The clinical utility of these agents will probably, however, reside in their side-effect profile. Both of these observations provide the impetus to develop clinically useful drugs that may impede the development of tolerance.

Tolerance, Addiction and Effective Pain Management
some thoughts by K.Trout
A major problem faced by narcotics users and abusers is the well-known development of tolerance when an opiate is given repeatedly over a period of time. This is directly responsible for a number of the problems associated with narcotic use and abuse since increasing tolerance requires that steadily larger doses be used to achieve the same effects or degree of pain relief.

This also underlies much of the crime associated with street addiction as the cost of maintaining a habit also escalates along with the dosage, often leading addicts to turn to drug dealing, prostitution or criminal activities to enable them to afford their daily dose.

Many experienced junkies, especially if heroin users, address this problem by taking regular breaks from their drug of choice, allowing their tolerance to diminish and their effective dosage to also be decreased. Due to the unpredictable quality of unregulated black-market street drugs this can actually be potentially dangerous if they then acquire material of greater potency than they were expecting. (Junkies who relapse after recovery face a similar risk when they return to use.)

Some users employ materials like cimetidine (Tagamet) to retard drug metabolism and thereby maximize their effectiveness.

Other users recommend grapefruit juice (Anonymous 2000) to interfere with the metabolism of the opiates by the liver and small intestinal Cytochrome P450 enzyme CYP3A and thus attempt to maximize their per dose effects, blood concentration and duration. While this has been reported by many users to be effective at maximizing per dose results this does not affect the development of tolerance.

Presently many questions remain, as there is also been some conjecture made that administration of grapefruit juice might interfere with the conversion of codeine to morphine due to its lesser inhibition of some CYP subfamilies. This does not seem to be the case; Caraco et al. 1996 reported (in animals) that if codeine was coadministered with selective inhibitors of CYP3A4 this could result in increased morphine production and enhanced effects due to ?shunting into the CYP2D6 pathway? (as CYP2D6 would NOT be affected).

It is worth noting that I can thus far locate NOTHING in the *scientific* literature specifically supporting the use of grapefruit juice to increase the general effectiveness of opiates or even that CYP3A is responsible for the metabolism of heroin. Although, it is certainly reasonable to assume that CYP3A is responsible for its metabolism since it is proven as such for other opioids such as codeine (Caraco et al. 1996) and fentanyl (Feierman & Lasker 1996)

Reports of successful application, circulating orally among users (Anonymous 2000 & 2001) and posted on web-based bulletin boards, are common enough that this should be investigated further.

It is important to keep in mind that grapefruit juice can also prove problematic due to the elevated levels of bioavailable drug, requiring a reduction of the dosage. Sometimes it can even be dangerous if certain other drugs are being used. The combination of grapefruit juice with some specific pharmaceuticals has produced many serious problems and even some deaths. (Ameer & Weintraub 1997; Dresser et al. 2000)

Another practice reportedly employed by some narcotic users is combining hydroxyzine with opiates to potentiate their effects. This is said to produce a rough doubling of intensity with the addition of unwanted side effects like a dry mouth. It appears to have no effect on the development of tolerance.

An interesting approach is the combination of opiates with the opiate antagonists naloxone or naltrexone in miniscule amounts. The combination of less than 0.001% of what would be a normal dose of the antagonist with an opiate allows a far greater response (?at least 50%?) to the opiate which in turn permits a much lower effective dose to be used. It is also said to prevent respiratory depression, tolerance and addiction. This approach has apparently been patented (Crain & Shen 1996) and is being commercially developed by Pain Therapeutics.

Another interesting comment was made by Karl Jansen (2001) concerning the administration of small oral doses of ketamine being found to be of use in chronic pain clinic for ?greatly reducing? the development of tolerance (via blockade of NMDA receptors).

However, many people are unaware that both enhanced effectiveness of narcotic analgesics AND prevention or reversal of tolerance is readily achievable through the oral use of up to 200-250 mg of Proglumide <(DL)-4-Benzamido-N,N-dipropylglutaramic acid>.

The work of Watkins suggests there may be a therapeutic dosage window with diminished results above it but more detailed work to define this is apparently lacking.

Rather than simply augment the action of the opiates, proglumide actually interferes with the anti-opioid activity of the neuropeptide CCK.

The chronic administration of opiates, or spinal cord and other CNS injuries, elevates the level of Cholecystokinin (CCK) that is present. Such elevated levels exert an antagonistic effect on opioid activity resulting in significantly diminished analgesic effects. (Watkins et al. 1984; Xu et al. 1993 & 1994)

It is this rise in CCK levels that directly leads to the condition known as drug tolerance and the corresponding increase in its anti-opioid activity that requires the opiate user to use increasingly larger amounts to achieve the same effects.

This anti-opiate effect can be prevented or even reversed through the administration of CCK inhibitors such as proglumide. (Watkins et al. 1984)

Besides just interfering with the adverse action of CCK on opiate activity, proglumide is also known to augment the analgesic effect of opiates. Often this can provide a higher quality of analgesia for those patients who suffer from an incomplete response to pain medications.

Watkins & coworkers reported that proglumide reversed morphine tolerance and also 1) hastened the onset of analgesia, 2) increased the peak levels, and 3) prolonged the duration.

They suggested that not simply did this indicate that effective narcotic doses could be decreased but it also indicated that proglumide might be able to enhance the effects of other procedures, such as acupuncture, which involve endogenous opiates. (Watkins et al. 1984)

Proglumide is a nonselective CCK inhibitor that was formerly employed as an anti-ulcer medication (Hahne et al. 1981). It shows NO analgesic effects of its own.

Although proglumide is now considered to be an obsolete pharmaceutical due to changes in our understandings of ulcer etiology, it has already seen extensive pharmacological and toxicological testing proving its safety and has been approved for use in humans.

It has largely fallen into disuse but is still available in bulk via chemical houses or as a pharmaceutical in Europe and Africa sold under the trade name Milid and Milide.

Other CCK inhibitors show similar properties (Id?np??n-Heikkil? et al. 1997; Xu et al. 1993). However, beyond simply having seen previous use in humans, proglumide is both inexpensive and nontoxic. (Ott 1999)

Proglumide is not some sort of magic bullet for completely eliminating the risk of tolerance development and addiction as its effects are only effective for a limited duration before tolerance to IT begins to develop. (After 8 days its effectiveness begins to wane) The work of Kellstein & Mayer 1990 suggests that successful therapeutic/maintenance applications will probably require its discontinuation for a week after each week of use. More work is needed to better define the precise parameters of its effective use for this purpose.

Despite this, proglumide has already demonstrated itself to be of value both in pain management and as an adjunct to maintaining a narcotic addiction within a larger program of harm reduction (Anonymous 2000; Ott 1999).

What is fascinating is how few drug educators, drug treatment facilities or even drug users are aware of this despite it being readily available information for nearly 20 years.

If development of tolerance and the high price of a sustained addiction are truly as serious of a problem as we all agree that they are, one can only wonder how it is that, despite the tools existing to remove or at least reduce this problem, there seems to be no interest or research except on a limited scale related to specific small areas of chronic pain management and understanding.

The current misguided approach of substituting methadone is commonly reported to actually cause MORE perceptual and thinking problems than the opiates it replaces PLUS methadone is known to cause physical damage to internal organs that are not encountered with opiate use itself.

Harm reduction approaches would benefit greatly by using proglumide as a cornerstone and making it readily available to both narcotic users and abusers.

Those who will most certainly object include organized crime and drug dealers who enjoy the obscene profits reaped from escalating drug tolerances, and possibly also the so-called ?drug educators? that sadly often seem to be the ones most in need of some factual education.

There are many problems associated with opiate use and abuse. While the majority of these are legal in origin, the most sensible approach would be to ameliorate those that aren?t.

Increased analgesic effectiveness and prevention of tolerance are two obvious areas where harm reduction is readily possible
Both sufferers of chronic pain and narcotic addicts stand to benefit from having their needs met and their health risks simultaneously decreased.

As this is first and foremost a health problem, the current approach of harm maximization is both counterproductive and unacceptable. To a rationale or caring mind it might even be perceived of as unethical and amoral.

Not only do sufferers of chronic pain and narcotic addicts stand to benefit from such harm reduction approaches but, by decreasing drug-associated crimes, a significant area of the true ?drug problem? can be directly addressed, thereby benefiting society as a

 

[reformer]

Wrong compound- You mean peroxynitrite

I can pretty much guarantee that you don't mean peroxynitrate, but that you meant to post about peroxynitrite.

Peroxynitrite is formed from the covalent adduction of two VERY stable free-radicals, nitric oxide (N=O) and superoxide (O2-). Since these two radicals are quite non-reactive and long-lived, and are mostly produced in close proximity to each other by similar cell types, they have the opportunity to "find" each other and react with each other to form peroxynitrite (O=N-O-O-). They react together at near diffusion-controlled rates (nearly instantaneously) with a rate constant of about 4 x 10^7 M(-1)s(-1).

In contrast, peroxynitrate is formed by the analogous adduction of nitrite radical (O=N-O) and superoxide. Nitrite radical is only formed in vanishingly low amounts, usually through oxidation of nitrite by myeloperoxidase, and so incredibly reactive (nearly as oxidizing as hydroxyl radical (HO)), that it immediately reacts with, for example, tyrosine to form nitrotyrosine. Nitrite radical has no chance to form peroxynitrate with superoxide in the fashion that nitric oxide does with superoxide.

As to your question about antioxidants serving to scavenge peroxynitrite (not peroxynitrate), in my opinion ascorbate is a rather shoddy choice. Ascorbic acid has a pKa of about 4.5 and peroxynitrite has a pKa of about 6.6. This means that BOTH ascorbate and peroxynitrite will be ionized and anionic at physiological pH. Ypycially, two anions do not like to react with each other, as the negative charges induce repulsion from each other.

A better approach would be to use N-Acetyl-Cysteine to boost endogenous levels of glutathione which is the body's natural thiol (sulfur)-based antioxidant. Thiols scavenge peroxynitrite quite readily, and their pKa is about 9-9.5 so that they are neutral, not anionic, and will not suffer from the repulsion of two negative charges that hampers the ascorbate/peroxynitrite reaction.

So, eat more N-Acetyl-Cysteine, and I'd also load up on Alpha Lipoic Acid, a dithiol antioxidant with even greater reducing power than even glutathione.