Guanidine

Guanidine is a strong organic base used to treat muscle weakness and fatigue associated with the myasthenic complications of Eaton-Lambert syndrome[1]. It is found in the urine as a normal product of protein metabolism and is also used in laboratory research as a protein denaturant[1]. Guanidine is a small, nitrogen-rich organic compound found in nature in plants and animals[3]. It exists at ambient conditions and is slightly soluble in water, but its hydrochloride salt is highly water-soluble and is the usual article of commerce[3]. The free base is extremely toxic[3].

Guanidine is indicated for the reduction of the symptoms of muscle weakness and easy fatigability associated with the myasthenic syndrome of Eaton-Lambert[2]. It is not indicated for treating myasthenia gravis[2]. The Eaton-Lambert syndrome is ordinarily differentiated from myasthenia gravis by the usual association of the syndrome with small cell carcinoma of the lung, but myography may be necessary to make the diagnosis[2].

Guanidine apparently acts by enhancing the release of acetylcholine following a nerve impulse[2]. It also appears to slow the rates of depolarization and repolarization of muscle cell membranes[2]. Guanidine is contraindicated in individuals with a history of intolerance or allergy to this drug[2]. Fatal bone-marrow suppression, apparently dose related, can occur with guanidine[2]. Safe use of guanidine hydrochloride in pregnancy has not been established[2]. Therefore, the benefits of therapy must be weighed against the potential hazards. Because guanidine is excreted in milk, patients on this drug should discontinue breastfeeding[2]. Since there is inadequate experience in children who have received this drug, safety and efficacy in children have not been established[2].

Baseline blood studies should be followed by frequent red and white blood cell and differential counts[2]. The drug should be discontinued upon appearance of bone-marrow suppression[2]. Concurrent therapy with other drugs that may cause bone-marrow suppression should be avoided[2]. Renal function may be affected in some patients receiving guanidine[2]. Patients should therefore have regular urine examinations and serum creatinine determinations while taking this drug[2]. Physicians should be given adequate precautions pertaining to the gastrointestinal side effects and the possibility of induced behavior disorders[2]. Treatment should not be continued longer than necessary[2].

Anemia, leukopenia, and thrombocytopenia resulting from bone-marrow suppression attributable to guanidine have been reported[2]. Other adverse reactions that have been observed are: General: sore throat, rash, fever[2]. Neurologic: paresthesia of lips[2]. Guanidine is medication that treats Lambert-Eaton myasthenic syndrome[4]. This condition causes your body to interfere with a chemical needed for nerve cells to “tell” your muscle fibers to contract[4]. This medication comes as a tablet that you can take by mouth with a glass of water as directed[4].

Citations:

[1] https://go.drugbank.com/drugs/DB00536

[2] https://www.merck.com/product/usa/pi_circulars/g/guanidine_hydrochloride/guanidine_pi.pdf

[3] https://www.acs.org/molecule-of-the-week/archive/g/guanidine.html

[4] https://my.clevelandclinic.org/health/drugs/20528-guanidine-oral-tablets

[5] https://en.wikipedia.org/wiki/Guanidine