Paolo Giacomoni, PhD, Insight Analysis Consulting09.01.22
In recent months, many of the topics that I’ve written about have their impetus in mined Google data. Visitors to Happi.com are searching for answers to a host of disparate questions and I’ve taken on the responsibility to answer them. This month’s column is focused on Methenamine which, at first glance, may seem beyond the scope of Happi coverage.
Methenamine belongs to the family of medicines called anti-infectives. It is administered via the general route to eliminate bacteria that cause infections of the urinary tract. It is generally used to treat chronic infections and to prevent their recurrence. Due to an increasing population of antibiotic-resistant microorganisms, methenamine seems to be a promising strategy for prevention of recurrent urinary tract infections (UTIs) insofar as, properly speaking, it is not an antibiotic. As a matter of fact, methenamine releases formaldehyde in acidic environments such as urine, and as a result it has general antibacterial activity in the urinary tract and possibly elsewhere. There are two different salt forms of methenamine available via prescription, Methenamine Hippurate and Methenamine Mandelate, as well as several over-the-counter (OTC) products containing methenamine.
The microbial etiology of urinary infection has been studied in depth. Escherichia coli is found in about 80% of the cases, and Staphilococcus saprofiticus is present in 10-15% of the cases. Several factors facilitate the onset of UTIs, including age, diabetes and catheterization. Senior citizens and diabetic patients have an impaired immune system and are, therefore, prone to infections. People whose urinary tract is accessible to microorganisms because of the insertion of a catheter are also prone to UTIs. Indeed, a urinary catheter is a long, flexible tube used to empty the bladder and collect urine in a drainage bag. It can be inserted through the urethra or through a small opening made in the lower abdomen, thus potentially allowing environmental microorganisms to access the bladder.
UTIs are not considered to be sexually transmitted infections (STIs), because their onset can follow different mechanisms. And yet, UTI-provoking bacteria can be shared between sexual partners and can be said to be sexually transmissible. Epidemiological research1 shows that that sexually active women have more UTIs than women who are not. People who practice insertive anal intercourse are at higher risk for UTI as compared to people practicing insertive vaginal intercourse only. Some sexual partners might share UTI-causing bacteria even in oro-genital relationships. Good hygiene of the perineum is therefore essential for all people before and after sex.
The perineum is the anatomical region located between the anus and the scrotum in males and the anus and the vulva in females. It is important to keep in mind that the perineum is inhabited by a variety of microorganisms, originating from the intestinal microbiome as well as from the vaginal microflora. Vaginal secretions are different in cis-women and in trans-women: in cis-women the vaginal microflora is mainly composed by lactobacilli and gardnerellae whereas in trans-women, porphyromonas, peptostreptococci and prevotellae are preponderant;2 this can modify the chances of the onset of UTIs. For instance, UTIs are more frequent in perimenopausal women, whose vaginal secretion have higher pH and favor the growth of a microflora composed mainly of Enterobacteriaceae, than in healthy young or adult cis-women whose low-pH vaginal secretions favor the growth of lactobacilli.
UTIs are less common in males. It has been pointed out that this is perhaps due to their anatomy: a penis has a long urethra and this means bacteria have farther to travel to reach the urinary tract system and cause infection.
Anecdotal recommendations to reduce the risk of urinary tract infections suggest drinking plenty of liquids, especially water or cranberry juice. Drinking water is expected to help dilute one’s urine and stimulate frequent urination, thus flushing bacteria from one’s urinary tract before an infection can begin. Perhaps more important is to wipe from front to back. Doing so after urinating or after a bowel movement might limit bacterial spreading from the perineum to the vagina. Feminine products with irritating detergents should be avoided. Good hygiene does not necessarily mean cleaning with harsh detergents! Using deodorant sprays or other feminine products in the genital area can unbalance the microflora and allow pathogens to colonize the perineal region.
An interesting observation that has been recently published3 points out that the use of soap and water to wash the perineum had a smaller effect on reducing the rate of UTI than using water alone. Washing with water seems to be “protective” whereas washing with soap and water seems to be “predisposing.” Washing with water probably also removes pathogenic microorganisms thereby preventing infections whereas washing with soap probably removes commensal organisms and favors the colonization by UTI-associated pathogens.
Methenamine can also be used against hyperhidrosis.4 In a gel stick formulation, methenamine decreased palmar and plantar sweating in 24 of 26 individuals in a double-blind, placebo-controlled study.
Interestingly enough, even though methenamine acts by the slow release of formaldehyde, one patient with formaldehyde sensitivity was able to use the methenamine gel stick without difficulty.
Approximately one third of the patients experienced some continuing relief for one to three weeks after discontinuing the trial medication. One can therefore conclude that methenamine is a safe, effective addition to the available types of topical therapy for essential hyperhidrosis. Indeed, methenamine is also used in antiperspirants to prevent sweating within the sockets of prosthetic devices for amputees.
All this seems to indicate that methenamine could be a safe and effective ingredient for personal care products. It is found on the “web” that methenamine is accepted for use by the European Economic Community (EEC) as a preservative at a concentration no greater than 0.15%. and that methenamine may also be added to cosmetic products at a concentration greater than 0.15% for other specific uses.
References
Paolo Giacomoni, PhD
Insight Analysis Consulting
paologiac@gmail.com
516-769-6904
Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as executive director of research at Estée Lauder and was head of the department of biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents.
Methenamine belongs to the family of medicines called anti-infectives. It is administered via the general route to eliminate bacteria that cause infections of the urinary tract. It is generally used to treat chronic infections and to prevent their recurrence. Due to an increasing population of antibiotic-resistant microorganisms, methenamine seems to be a promising strategy for prevention of recurrent urinary tract infections (UTIs) insofar as, properly speaking, it is not an antibiotic. As a matter of fact, methenamine releases formaldehyde in acidic environments such as urine, and as a result it has general antibacterial activity in the urinary tract and possibly elsewhere. There are two different salt forms of methenamine available via prescription, Methenamine Hippurate and Methenamine Mandelate, as well as several over-the-counter (OTC) products containing methenamine.
Urinary Tract Infections
Urinary tract infections occur when bacteria or other microorganisms invade the drainage system of the body. They usually occur in the bladder or in the urethra; that is, the tube that carries urine out of the bladder. More serious infections involve the kidneys. Normally, the immune defense scavenges these microorganisms before they can grow and multiply, but when the immune system is impaired, UTIs can occur. Most UTIs occur in the bladder (cystitis) and may cause pelvic pain, urge to urinate, pain with urination and blood in the urine. They can be treated with specific drugs. An untreated UTI can lead to complications, such as infection of the prostate gland in males or of the internal reproductive organs in females.The microbial etiology of urinary infection has been studied in depth. Escherichia coli is found in about 80% of the cases, and Staphilococcus saprofiticus is present in 10-15% of the cases. Several factors facilitate the onset of UTIs, including age, diabetes and catheterization. Senior citizens and diabetic patients have an impaired immune system and are, therefore, prone to infections. People whose urinary tract is accessible to microorganisms because of the insertion of a catheter are also prone to UTIs. Indeed, a urinary catheter is a long, flexible tube used to empty the bladder and collect urine in a drainage bag. It can be inserted through the urethra or through a small opening made in the lower abdomen, thus potentially allowing environmental microorganisms to access the bladder.
UTIs are not considered to be sexually transmitted infections (STIs), because their onset can follow different mechanisms. And yet, UTI-provoking bacteria can be shared between sexual partners and can be said to be sexually transmissible. Epidemiological research1 shows that that sexually active women have more UTIs than women who are not. People who practice insertive anal intercourse are at higher risk for UTI as compared to people practicing insertive vaginal intercourse only. Some sexual partners might share UTI-causing bacteria even in oro-genital relationships. Good hygiene of the perineum is therefore essential for all people before and after sex.
The perineum is the anatomical region located between the anus and the scrotum in males and the anus and the vulva in females. It is important to keep in mind that the perineum is inhabited by a variety of microorganisms, originating from the intestinal microbiome as well as from the vaginal microflora. Vaginal secretions are different in cis-women and in trans-women: in cis-women the vaginal microflora is mainly composed by lactobacilli and gardnerellae whereas in trans-women, porphyromonas, peptostreptococci and prevotellae are preponderant;2 this can modify the chances of the onset of UTIs. For instance, UTIs are more frequent in perimenopausal women, whose vaginal secretion have higher pH and favor the growth of a microflora composed mainly of Enterobacteriaceae, than in healthy young or adult cis-women whose low-pH vaginal secretions favor the growth of lactobacilli.
UTIs are less common in males. It has been pointed out that this is perhaps due to their anatomy: a penis has a long urethra and this means bacteria have farther to travel to reach the urinary tract system and cause infection.
Anecdotal recommendations to reduce the risk of urinary tract infections suggest drinking plenty of liquids, especially water or cranberry juice. Drinking water is expected to help dilute one’s urine and stimulate frequent urination, thus flushing bacteria from one’s urinary tract before an infection can begin. Perhaps more important is to wipe from front to back. Doing so after urinating or after a bowel movement might limit bacterial spreading from the perineum to the vagina. Feminine products with irritating detergents should be avoided. Good hygiene does not necessarily mean cleaning with harsh detergents! Using deodorant sprays or other feminine products in the genital area can unbalance the microflora and allow pathogens to colonize the perineal region.
An interesting observation that has been recently published3 points out that the use of soap and water to wash the perineum had a smaller effect on reducing the rate of UTI than using water alone. Washing with water seems to be “protective” whereas washing with soap and water seems to be “predisposing.” Washing with water probably also removes pathogenic microorganisms thereby preventing infections whereas washing with soap probably removes commensal organisms and favors the colonization by UTI-associated pathogens.
Methenamine in Personal Care
Since axillary malodors are the result of bacterial-induced digestion of long lipid chains, methenamine could be used in deodorants to kill bacteria and avoid volatile air-borne malodorant molecules.Methenamine can also be used against hyperhidrosis.4 In a gel stick formulation, methenamine decreased palmar and plantar sweating in 24 of 26 individuals in a double-blind, placebo-controlled study.
Interestingly enough, even though methenamine acts by the slow release of formaldehyde, one patient with formaldehyde sensitivity was able to use the methenamine gel stick without difficulty.
Approximately one third of the patients experienced some continuing relief for one to three weeks after discontinuing the trial medication. One can therefore conclude that methenamine is a safe, effective addition to the available types of topical therapy for essential hyperhidrosis. Indeed, methenamine is also used in antiperspirants to prevent sweating within the sockets of prosthetic devices for amputees.
All this seems to indicate that methenamine could be a safe and effective ingredient for personal care products. It is found on the “web” that methenamine is accepted for use by the European Economic Community (EEC) as a preservative at a concentration no greater than 0.15%. and that methenamine may also be added to cosmetic products at a concentration greater than 0.15% for other specific uses.
References
- Lema VM, Lema APV (2018) Sexual Activity and the Risk of Acute Uncomplicated Urinary Tract Infection in Premenopausal Women: Implications for Reproductive Health Programming. Obstet Gynecol Int J 9(1): 00303. DOI: 10.15406/ogij.2018.09.00303
- Birse, K.D., Kratzer, K., Zuend, C.F. et al. The neovaginal microbiome of transgender women post-gender reassignment surgery. Microbiome 8, 61 (2020). https://doi.org/10.1186/s40168-020-00804-1
- Lal D. Perineal hygiene in recurrent urinary tract infections - protective or predisposing? Antimicrob Resist Infect Control. 2015 Jun 16;4(Suppl 1):P263. doi: 10.1186/2047-2994-4-S1-P263. PMCID: PMC4475184.
- Cullen SI. Topical methenamine therapy for hyperhidrosis. Arch Dermatol. 1975 Sep;111(9):1158-60. PMID: 1167048.
Paolo Giacomoni, PhD
Insight Analysis Consulting
paologiac@gmail.com
516-769-6904
Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as executive director of research at Estée Lauder and was head of the department of biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents.