Huperzine A, Mestinon and Myasthenia Gravis

Huperzine A gets a lot of attention as a natural (and sometimes necessary) alternative to pyridostigmine bromide, especially when there are adverse side effects to the synthetic treatment option. So what is the best choice and how do we begin to navigate the options in front of us?

First of all, let’s define what exactly Huperzine A is. Huperzine A is a dietary supplement that is “derived from the Chinese club moss Huperzia serrata and works as a cholinesterase inhibitor — a type of medication that works by improving the availability of the neurotransmitter acetylcholine”, needed for muscle contraction. (1) By definition, this is a similar mechanism of action found in pyridostigmine, also known by the brand name of Mestinon. Pyridostigmine is also classified as a cholinesterase inhibitor which helps to inhbit “the destruction of acetylcholine by cholinesterase and thereby permits freer transmission of nerve impulses across the neuromuscular junction”. (2)

While Huperzine A has been used for centuries in the Chinese culture to treat everything from “rheumatism and colds, to relax muscles and tendons, and to improve blood circulation”, it gained attention as a potential use in the treatment of Alzheimer’s patients. (3) In recent years however, it has sparked interest in the potential treatment of Myasthenia Gravis as an alternative to pyridostigmine. Many cite adverse side effects and intolerable reactions to the pyridostigmine as a motivator for switching to Huperzine A. Others still prefer a more natural approach to their medication regimen.

It is important to know that Huperzine A has only been clinically studied, and at specific doses, in relation to Alzheimer’s disease. This has no clinical backing in the potential treatment of Myasthenia Gravis in the way of controlled studies. (3)

Let’s dig a little deeper though into how these two treatments break down in our bodies and are used to either our benefit or detriment.

• Side effects, adverse reactions and cholinergic crisis:
  Within the Myasthenic communities online, you may stumble upon individuals who have made the switch from the synthetic pyridostigmine to the natural Huperzine A, citing they could not tolerate an ambiguously defined set of side effects and/or adverse reactions. This is very important to talk about and unpack as much of the movement in favor for Huperzine A rests right here. Pyridostigmine bromide works by stimulating the parasympathetic nervous system, which inevitably includes an over stimulation of the gastrointestinal tract that can lead to bloating, cramping and diarrhea. (4) For many, these side effects can be harsh and debilitating both inside and outside the home and leave many with social hesitation or anxiety of being too far from the nearest bathroom. Pyridostigmine can also cause some mild muscular twitching and systemic cramping, although these side effects are notably and significantly less than their GI counterparts. (4) Understandably so, this would motivate anyone who experiences such side effects to seek a potentially more gentle alternative that is billed as safer and effective for those who made the switch.

• But, we need to talk about definitions here. Few have ever clarified if they experienced the above reactions and subsequently classified them as “adverse” or “side effects” or if there is more to the picture than meets the eye. You see, pyridostigmine, when taken in a greater dose than what is needed*, can cause what is called a cholinergic crisis which has the potential to produce adverse effects and potentially life threatening scenarios in it’s most severe form. These effects can come about in rapid sequence (usually they begin 45-60 minutes after ingesting an oral dose) and not all symptoms may present in all individuals. Moderate to severe twitching, miosis, excessive salivation and lacrimation, nausea, vomiting and severe diarrhea, severe GI cramping, difficulty breathing, swallowing and speaking, sweating and flushing are all part of the potential presentation. (4) Since it can mimic in presentation with a Myasthenic crisis (disease induced rather than medication induced), it is not always easy to pick up on, even with a trained eye, and can leave many assuming that it is simply an unpleasant side effect of the drug itself. This lack of clarity between true side effect and cholinergic crisis, even in a more mild to moderate form, leaves the Myasthenic with some of the puzzle pieces missing. *Please note that overdose is not the fault of the patient in that it is rarely intentional. As environmental factors and immune fluctuations occur, the need for pyridostigmine can vary and the lack of adjustment to those influencing factors often are the culprit in producing cholinergic crisis.
• Huperzine A, as noted above, has the same mechanism of action as does it’s synthetic counterpart, meaning that you have the exact same potential to repeat the side effects and cholinergic crisis risks as you did with pyridostigmine. It may take a much higher dose and the impact may be slightly minimized, but the risks are all still there. The selling point it is safer since it is natural. Again, we need to go back to definitions in order to get a clearer picture of what safer with any treatment really means. As it currently stands, “safer” is a loaded word with ambiguous meaning here. We have already talked about it being in the same class as pyridostigmine and working on the same mechanism which, ergo, offers the same risks. Huperzine A still must be processed by the kidneys and liver, just like the synthetic version and it’s renal toxicity is almost identical. (3,4) But we must also recognize that, as a dietary supplement, it is unregulated and that makes it more difficult to ensure safety, efficacy and viability. There are no studies or trials that offer patients or treating physicians a standard for dosing, peaks and falls like we see in pyridostigmine, further augmenting the potential for cholinergic danger and under dosing.
• The typical half life of pyridostigmine bromide is 3- 4 hours after renal elimination with an estimated half life of Huperzine A to be an estimated 10-14 hours after renal elimination. (3,5) This astounding difference in half life clearance solidifies a marked difference in safe dosing regimens, further augmenting the concerns over the lack of regulation in ingredients and the absence clinical studies to offer up a clear understanding of integral information (ie., when peak release and half-life begins and ends etc..). This leaves both patient and physician zero dosing standard and narrowly contributes a vague and unchecked approach to treatment.

Lack of access, cost and delayed diagnosis can leave many without alternative options other than to reach for Huperzine A and there are those who firmly believe that Huperzine A helps them control their Myasthenia Gravis with fewer side effects than pyridostigmine. While these scenarios and individuals may find great success with their switch to Huperzine A, it begs discernment and caution in understanding all of the potential pros and cons before moving forward.

Author: Rebekah Dorr
Founder & Administrator, Myasthenia Gravis Unmasked

References:
(1) (http://www.mayoclinic.org/diseases-conditions/alzheimers-disease/expert-answers/huperzine-a/faq-20058259)

(2) (Miller RD. Pharmacodynamics and pharmacokinetics of anticholinesterase. In: Rueg-heimer E, Zindler M, ed. Anaesthesiology. [Hamburg, Germany: Congress; Sep 14-21,1980; 222-223.] [Int Congr. No. 538], Amsterdam, Netherlands: Excerpta Medica; 1981)

(3) (https://www.drugs.com/pro/pyridostigmine.html)

(4) (http://www.mims.com/malaysia/drug/info/pyridostigmine%20bromide/?type=brief&mtype=generic)

(5) (https://www.medicines.org.uk/emc/medicine/865)