Treatment of Recurrent Urinary Tract Infection Symptoms with Urinary Antiseptics Containing Methenamine and Methylene Blue: Analysis of Etiology and Treatment Outcomes

Abstract

Purpose
Urinary antiseptics including methenamine and methylene blue are used in the symptomatic treatment of urinary tract infections (UTIs).

Patients and Methods
This was a prospective, double-blind, randomized, double-dummy safety and efficacy study of 2 urinary antiseptic combinations in the symptomatic treatment of recurrent cystitis: methenamine 120mg + methylene blue 20mg (Group A) versus acriflavine 15mg + methenamine 250mg + methylene blue 20mg + Atropa belladonna L. 15mg (Group B). All subjects underwent pretreatment urine culture and antibiotic sensitivity tests prior to 3-day oral treatment with study drug, followed by 3 days of antibiotic therapy (based on urine culture) + study drug treatment. Efficacy was evaluated using the Urinary Tract Infection Symptoms Assessment Questionnaire (UTISA). The primary endpoint was the percentage of patients presenting improvement in cystitis manifestations on the UTISA domain “Urination Regularity” at Visit 2. The primary safety variable was the incidence of treatment-related adverse events.

Results
A total of 144 subjects were randomized per group and 272 completed the study. Primary endpoint analysis demonstrates homogeneity between treatment groups, with 69.4% and 72.2% subjects, respectively, showing improvement in the score of the urinary regularity UTISA domain after 3 days of treatment (p= 0.87). At Visit 2, incidence of treatment-related adverse events was higher in Group B (Group A: n= 11, Group B: n= 31, p= 0.0057).

Conclusion
Both treatments were effective in reducing UTI symptoms assessed by UTISA questionnaire after 3 days of treatment. The two regimens were comparable in incidence of adverse events, but the combination of methenamine + methylene blue resulted in fewer treatment-related adverse effects.

Full text

ORIGINAL RESEARCH
Treatment of Recurrent Urinary Tract Infection
Symptoms with Urinary Antiseptics Containing
Methenamine and Methylene Blue: Analysis of
Etiology and Treatment Outcomes
This article was published in the following Dove Press journal:
Research and Reports in Urology
Carlos Romualdo Barbosa
Gama
1
Manoel Antônio Gonçalves
Pombo
1
Carlos Pereira Nunes
1
Gustavo Falcão
Gama
1
Spyros GE Mezitis
2
Mendel Suchmacher Neto
3
Oscar Roberto Guimarães
1
Mauro Geller
1,4
Lisa Oliveira
4
Adenilson de Souza da Fonseca
1
Aline Sitnoveter
1
Gerson Goldwasser
3
Karin Soares Cunha
5
Luiz Guilherme Darrigo
Junior
6
1
UNIFESO Medical School, Rio de Janeiro,
Brazil;
2
New York-Presbyterian Hospital/
Weill-Cornell Medical Center, New York,
NY, USA;
3
Santa Casa de Misericórdia do
Rio de Janeiro, Rio de Janeiro, Brazil;
4
Universidade Federal do Rio de Janeiro
(UFRJ), Rio de Janeiro, Brazil;
5
Pathology
Department, Faculdade de Medicina -
Universidade Federal Fluminense (UFF),
Niterói, Brazil;
6
Ribeirão Preto Medical
School, University of São Paulo, Ribeirão
Preto, Brazil
Purpose: Urinary antiseptics including methenamine and methylene blue are used in the
symptomatic treatment of urinary tract infections (UTIs).
Patients and Methods: This was a prospective, double-blind, randomized, double-dummy
safety and efcacy study of 2 urinary antiseptic combinations in the symptomatic treatment
of recurrent cystitis: methenamine 120mg + methylene blue 20mg (Group A) versus acri-
avine 15mg + methenamine 250mg + methylene blue 20mg + Atropa belladonna L. 15mg
(Group B). All subjects underwent pretreatment urine culture and antibiotic sensitivity tests
prior to 3-day oral treatment with study drug, followed by 3 days of antibiotic therapy (based
on urine culture) + study drug treatment. Efcacy was evaluated using the Urinary Tract
Infection Symptoms Assessment Questionnaire (UTISA). The primary endpoint was the
percentage of patients presenting improvement in cystitis manifestations on the UTISA
domain “Urination Regularity” at Visit 2. The primary safety variable was the incidence of
treatment-related adverse events.
Results: A total of 144 subjects were randomized per group and 272 completed the study.
Primary endpoint analysis demonstrates homogeneity between treatment groups, with 69.4%
and 72.2% subjects, respectively, showing improvement in the score of the urinary regularity
UTISA domain after 3 days of treatment (p= 0.87). At Visit 2, incidence of treatment-related
adverse events was higher in Group B (Group A: n= 11, Group B: n= 31, p= 0.0057).
Conclusion: Both treatments were effective in reducing UTI symptoms assessed by UTISA
questionnaire after 3 days of treatment. The two regimens were comparable in incidence of
adverse events, but the combination of methenamine + methylene blue resulted in fewer
treatment-related adverse effects.
Keywords: urinary tract infection; UTI, urinary antiseptics, UTISA, methenamine,
methylene blue
Introduction
Urinary tract infections (UTIs) are common bacterial infections occurring in both
hospital and community settings, affecting individuals of both sexes and in all age
ranges.
1
Among individuals under 50 years of age, the incidence of UTIs in males
is low, with women being up to 30 times more likely to develop a UTI.
2
The
increased risk among women is attributed to facilitated bacterial entry into the
urinary tract on account of anatomical factors including a shorter urethra and
urethral proximity increasing contact with vaginal and rectal pathogens, in addition
Correspondence: Mauro Geller
Av. Ataulfo de Paiva, 135 sl. 1104, Rio de
Janeiro, RJ 22440-901, Brazil
Tel +55 21 3875-6660
Fax + 55 21 2259-3395
Email maurogeller@gmail.com
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to incomplete voiding of the urinary bladder and exposure
to pathogens during intercourse.
2,3
Approximately 90% of
UTIs are caused by Escherichia coli bacteria, which can
be found in the stool and can colonize the urethra, causing
urethritis, the urinary bladder (cystitis), and eventually
reaching the kidneys (pyelonephritis).
1,3,4
Uropathogens
other than E. coli, including Klebsiella pneumoniae,
Enterobacter spp., P. aeruginosa, Proteus mirabilis, and
Enterococcus spp., are most often identied in UTIs
among patients under risk factors (RF) for complicated
UTIs.
2
RFs for UTIs among women include sexual activity,
diaphragm and spermicide use, genetic predisposition fac-
tors, change in sexual partner, previous UTIs, and post-
menopausal state.
2,4,5
Uncircumcised men present a higher
risk of a UTI compared to circumcised men, and have
a higher risk with advancing age due to prostatic
hypertrophy.
6
Other RFs include urinary catheterization,
surgery involving the urinary tract, anatomical alteration
or blockage of the urinary tract, inability to fully void the
bladder, pregnancy, diabetes, and aged over 65 years.
7–9
The European Association of Urology’s ORENUC
classication system straties UTIs according to clinical
presentation, RFs, and severity.
9
In this system, adults
presenting with uncomplicated UTIs are classied as
O (no known/associated RF), R (Recurrent UTI RF, but
no risk of severe outcome), and sometimes E (Extra-
urogenital RF, with risk of more severe outcome)
classes, while complicated UTIs are categorized as
N (Nephropathic disease, with risk of more severe out-
come), U (Urological RF, with risk of more severe out-
come, which can be resolved during therapy) and
C (Permanent urinary catheter and non-resolvable urolo-
gical RF, with risk of more severe outcome).
1,9
The
typical signs and symptoms of urethral and bladder
infection include pollakiuria, alguria and burning on
urination, suprapubic discomfort, vesical tenesmus,
malaise, cloudy urine or presence of blood, and low
fever.
1
In cases of pyelonephritis, the symptoms include
high fever, headache, chills and low back pain.
1,3
The
patient may also present a complete clinical picture of
UTIs, with cystitis and pyelonephritis.
4
Diagnosis is
usually based on history and physical examination, and
may be complemented with urinalysis and urine
culture.
9,10
UTI treatment objectives include alleviating symptoms
and eliminating the causative agent, thus preventing infec-
tion dissemination and the formation of parenchymatous
lesions.
7,11
The most commonly employed antibiotics
include trimethoprim sulfamethoxazole, uoroquinolones,
and cephalosporins.
4,7,12
Recurrence of UTIs is common, especially in female
patients.
5
Recurrent UTIs are associated with both perso-
nal (social and psychological impact negatively affecting
quality of life) and societal (clinical and economic) disease
burden.
2,10
Consultations for UTIs account for 1–6% of all
medical visits, with an annual cost of approximately US
$1.6 billion.
11
Preventive measures for UTI recurrence
include change of contraceptive method, increased uid
intake, urination after sexual activity, long-term antibiotic
therapy, consumption of cranberry juice and fruit products,
and urinary antiseptics.
7,13
Methenamine is a urinary antiseptic commonly used in
the prophylaxis and treatment of chronic and recurrent
uncomplicated lower UTIs.
13,14
Its bactericidal properties
are due to the release of formaldehyde by hydrolysis in
acid pH environments, to which most Gram-positive and
Gram-negative bacteria are susceptible.
13
Methylthioninium hydrochloride, also known as methy-
lene blue, is a thiazine dye related to the monoamine oxidase
inhibitor group that exhibits urinary antiseptic action upon
oral administration following reduction to leukomethylene
blue.
15
Repeated and long-term use of both methenamine
and methylthioninium hydrochloride as urinary antiseptics is
considered attractive since there is no bacterial resistance
development.
16
In this study, we sought to investigate use of
the combination of methenamine and methylene blue, avail-
able in commercially available oral formulations in Brazil
(Sepurin
®
and Cystex
®
), in the symptomatic relief of cystitis
prior to initiation of antibacterial treatment.
Patients and Methods
Study Design
This was a double-blind, randomized, double-dummy,
comparative study in parallel groups of patients with
recurrent cystitis (dened as ≥2 episodes within the last
6 months) performed at UNIFESO in the State of Rio de
Janeiro, Brazil. The primary objective of this study was to
evaluate the use of the combination of methenamine and
methylene blue in the treatment of recurrent cystitis. The
secondary objectives were to evaluate safety and efcacy
of the combination of methenamine and methylene blue in
the treatment of cystitis symptoms, and to compare the
efcacy and safety of the combination of methenamine
and methylene blue versus the combination of acriavine
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+ methenamine + methylene blue + Atropa belladonna
L. in the treatment of cystitis symptoms.
Written informed consent was obtained from each
patient. The protocol was conducted in accordance with
the Declaration of Helsinki and Good Clinical Practice
guidelines. The study protocol and related documents
received approval from the institution’s ethical committee
(Comitê de Ética em Pesquisa do UNIFESO approval no.
2.434.612) and the study was registered at ClinicalTrials.
gov under the number NCT03379389.
Patient Population
Inclusion criteria specied age ≥18 years, recurrent cysti-
tis, and required that female patients be neither pregnant
nor breastfeeding and used birth control during the treat-
ment period. Subjects presenting history of nephritis or
renal calculi, diabetes, open-angle glaucoma or anatomical
changes contributing to recurrent cystitis (as evidenced by
imaging exams) were not included in the study. Subjects
with urine culture identifying Proteus spp. and
Pseudomonas spp. were withdrawn at Visit 2.
Study Procedures
After obtaining informed consent and screening for inclu-
sion and non-inclusion criteria, subjects were randomized
into one of two treatment groups in order of arrival to
study center.
The randomization list was generated using a random-
allocation software. Randomization was generated sequen-
tially, at a ratio of 1:1 for two treatment groups, in blocks of
10. Table 1 summarizes the schedule of study procedures. At
Visit 1, randomized subjects underwent pretreatment assess-
ments (medical history, physical exam, vital signs, cystitis
history), and urine was collected for culture and antibiotic
sensitivity tests. Visit 2 occurred at the end of 3 days of
treatment with the urinary antiseptics; patients returned to
the study center for evaluations, and antibiotic therapy was
initiated based on the urine culture/bacterial sensitivity
result. Visit 3/Final Study Visit occurred after 3 additional
days of treatment with antibiotic and study medication.
Efcacy was evaluated using the Urinary Tract Infection
Symptoms Assessment Questionnaire (UTISA).
17
Using this
questionnaire, the patient assessed the degree of severity and
bothersomeness on a scale of 0–3 (0= absence of symptom;
3= most severe/bothersome) of the following 7 UTI symp-
toms: urgency of urination, frequency of urination, pain or
burning when passing urine, urinary retention, pressure in
the lower abdomen or pelvic area, lower back pain, and
blood in the urine. The UTI symptoms scored with the
UTISA are divided into four domains: urination regularity,
problems with urination, pain associated with UTIs and
hematuria. The questionnaire also includes an overall rating
of UTI severity on a scale of 0 (no symptoms) to 3 (severe
symptoms). Follow-up UTISA includes two questions
regarding improvement from previous evaluation, (0=
about the same; 1= better; 2= worse), and how much
improvement from previous evaluation, on a scale of 1–6
(1= a little better; 6= a very great deal better).
The investigating physician also evaluated patient global
condition on a 10-point scale with 1 point representing the
worst possible evaluation and 10 the best possible global
condition. Overall efcacy and tolerability were evaluated by
the investigating physician during the nal study visit, who
classied both as “Very Good,” “Good,” “Fair” or “Poor.”
Safety evaluations throughout the treatment period
included adverse event monitoring, in terms of: occurrence,
Table 1 Schedule of Study Procedures
Study Visit Visit 1 Visit 2 Visit 3
Study Day Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6
Inclusion/Exclusion Criteria x
Randomization x
Physical Exam x x x
Laboratory Tests x x
Urine Culture + Bacterial Sensitivity x
UTISA Questionnaire x x x
Physician Assessment x x x
Adverse Event Monitoring x x x x x x x
Concomitant Medication Monitoring x x x x x x x
Oral Urinary Antiseptic Treatment x x x x x x
Oral Antibiotic Treatment x x x
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severity (mild/moderate/severe), duration and causality (rela-
tion to study medication) as well as monitoring of laboratory
tests performed at each study visit, including: CBC, fasting
blood glucose, AST, ALT, urea, uric acid, and creatinine.
Study Drugs
Urinary Antiseptics
Subjects were randomized into one of two treatment groups:
Group A or Group B. Group A received a combination of
120mg methenamine and 20mg methylthioninium at the
dose of 2 coated tablets, 3 times a day. Group B received
a combination of 15mg acriavine + 250mg methenamine +
20mg methylthioninium + 15mg Atropa belladonna L., at the
dose of 3 coated tablets, twice daily. Treatment duration with
urinary antiseptics lasted a total of six consecutive days. The
urinary antiseptics were administered in double-dummy
fashion in order to maintain double-blind evaluation between
the two treatments.
Antibiotic Therapy
At Visit 2, patients were prescribed open-label antibiotic
therapy based on the results of the urine bacterial sensitiv-
ity testing performed at Visit 1. Treatment duration was
determined on an individual basis, depending on the anti-
biotic prescribed according to the urine bacterial sensitiv-
ity test result.
Statistical Analysis
The primary study endpoint was the percentage of patients
presenting improvement in cystitis manifestations on the
UTISA domain “Urination Regularity” at Visit 2.
Secondary endpoints included Visit 2 evolution of the
total UTISA score, evolution of the remaining UTISA
domain scores, percentage of subjects with improvement
in UTISA question 9 (changes in UTI severity), and the
incidence of adverse events related to the study medication
in each treatment group.
Sample size determination was based on the primary
endpoint, estimating a difference between proportions with
a two-tailed test, with an alpha of 0.05 and power of
90.2%. The study n was determined with 109 patients
per treatment group, considering a maximum acceptable
difference between the treatment groups of 0.20. Based on
these parameters it would be possible to report the differ-
ence between proportions with an accuracy of approxi-
mately 0.12 points (95% condence interval). Taking
into account an estimated 30% loss rate (dropouts, loss
of follow-up and withdrawal of patients with positive
cultures for Proteus spp. and Pseudomonas spp.), the
total number of subjects required for this study was 284
evaluable patients.
Study data were analyzed using GraphPad Prism soft-
ware, version 8.4.3 for Windows (GraphPad Software, San
Diego, California USA, www.graphpad.com). Baseline
and demographic data were compared between groups
using unpaired t-test or Fisher’s exact test for continuous
and categorical variables, respectively. Primary and ef-
cacy endpoint analysis was performed using the Fisher’s
exact test for the intent-to-treat (ITT) population. For
analysis of continuous variables, data were analyzed for
the ITT population using mixed effects analysis followed
by Tukey’s multiple comparisons test. For comparisons of
categorical variables, we used the χ2 or Fisher’s test, or
mixed effects analysis for repeated measures.
Results
Subject Disposition
A total of 503 subjects were screened between March and
November 2018 and 288 subjects were randomized to
treatment, with 144 subjects in each treatment group
(Figure 1). Sixteen subjects were removed at the end of
Visit 2 for the following reasons: Adverse event (Group A:
n= 1; Group B n= 3); Urine culture positive for Proteus
spp., (Group A: n= 1; Group B: n= 1); Need for parenteral
antibiotics (Group A: n= 3; Group B n= 3); Withdrawn
consent (Group A: n= 3; Group B: n= 1). A total of 272
subjects completed the study, 136 per treatment group.
Baseline Characteristics
The demographic and pretreatment data are summarized in
Table 2. With the exception of mean participant age, where
there was a statistically signicant difference between the
two treatment groups, pretreatment and demographic char-
acteristics were comparable between groups. A majority of
patients in both treatment groups reported previous cystitis
treatment with antibiotics and half of all patients in both
treatment groups reported previous treatment with urinary
antiseptics.
Table 3 displays the UTISA total and domain scores at
each study visit. Mean pretreatment UTISA total domain
scores were comparable between treatment groups (19.0
and 17.8 in Group A and Group B, respectively; p= 0.11).
Pretreatment patient overall UTI severity assessment was
comparable between groups (Group A: 15 patients with
score of 1, 80 patients with score of 2 and 49 patients with
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score of 3; Group B: 26 patients with score of 1, 67
patients with score of 2 and 51 patients with score of 3;
χ2= 4.141, df= 3; p= 0.247) Physician global evaluation
scores at pretreatment were also comparable between
treatment groups (p= 0.097).
Results at Visit 2 (3 Days of Treatment)
Study Drug Efcacy
Analysis of the primary endpoint (UTISA domain
“Urination Regularity” after 3 days of treatment) reveals
homogeneity between treatment groups (χ2= 0.278; df= 2;
p= 0.87), with 69.4% and 72.2% of patients in Group
A and Group B, respectively, showing signicant score
improvement after 3 days of treatment (mean reduction of
−6.778 in Group A and −8.813 in Group B; p<0.0001 for
both groups).
Table 3 displays the UTISA total and domain scores at
each study visit. In both treatment groups there was
a statistically signicant improvement in total UTISA scores
at Visit 2 (p<0.0001) in relation to pretreatment scores.
Figure 2 displays the results of the UTISA domains
“Urination Regularity,” “Problems with Urination,” “Pain
Associated with UTI,” and “Hematuria” at Visit 2 in rela-
tion to Visit 1. Analysis of the secondary endpoint evalu-
ating the scores of the remaining UTISA domains
(“Problems with Urination,” “Pain Associated with UTI,”
and “Hematuria”), showed there was no between-group
difference in the percentage of patients in each group
presenting improvement of scores in relation to pretreat-
ment in the domains “Problems with Urination” (93.8%
and 95.8% of patients presenting improvement in Group
A and Group B, respectively) and “Pain Related to UTI”
(63.9% and 68.1% of patients presenting improvement in
Group A and Group B, respectively). There was no change
in either treatment group in the “Hematuria” domain (no
patients reported hematuria during the study).
In the “Overall UTI Severity” evaluation of the UTISA
at Visit 2 (Figure 3), there was a statistically signicant
(p<0.0001) improvement observed in both treatment
groups in relation to pretreatment assessment, with no
signicant difference between treatment groups at Visit 2
(χ2= 3.245, df= 3; p= 0.3554).
In the evaluation of percentage of subjects with
improvement in UTISA question 9 (changes in UTI
Figure 1 Flowchart of patients through the study.
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severity), 88.2% of patients in Group A and 94.4% of
patients in Group B reported improvement in UTI symp-
toms, with no signicant between-group difference (p=
0.1087). The degree of improvement of UTI symptoms
did not vary between patient groups at Visit 2 (χ2= 3.170;
df= 5; p= 0.6737).
In both Group A and Group B, Physician Global
Assessment scores showed signicant improvement
(p<0.0001) at Visit 2 in relation to pretreatment values,
with no signicant between-group difference (χ2= 10.61;
df= 9; p= 0.304).
Urine Culture and Bacterial Sensitivity Results
Most of the patients in both treatment groups showed
E. coli growth in the urine culture. The results of the
urine cultures and bacterial sensitivity test result/antibiotic
prescribed are displayed in Table 4.
Results at Visit 3 (End-of-Study)
Efcacy Evaluations
Total UTISA scores at Visit 3 showed signicant
(p<0.0001) reduction as compared to pretreatment scores
in both Group A and Group B (mean reduction of −19,98
in Group A and −18,53 in Group B), with 114/136 and
101/136 patients in Group A and Group B, respectively,
reporting absence of all UTI symptoms on the UTISA
questionnaire (χ2= 4.497; df= 3; p= 0.213) and maximum
score of improvement in relation to pretreatment, with no
signicant between-group difference (χ2= 7.446; df= 4; p=
0.1141). Visit 3 UTISA scores for the domains of
“Urination Regularity,” “Problems with Urination,” and
“Pain Related to UTI” showed signicant improvement
in relation to pretreatment values (p<0.005 for all domains
in both treatment groups), with no signicant between-
group differences observed, while the “Hematuria” domain
did not vary from pretreatment (no patients reporting
hematuria). Physician Global Assessment scores at Visit
3 were signicantly improved in relation to pretreatment,
with no difference between Group A and Group B (χ2=
15.46; df= 9; p= 0.0792).
Safety Evaluations
The primary safety variable was the incidence of adverse
events related to the study medication in each treatment
group. At Visit 2, 21 patients in Group A reported a total of
28 adverse events, while 32 patients in Group B reported
a total of 51 adverse events, with no difference between
treatment groups in the percentage of patients presenting
adverse events (p=0.746) (Table 5). However, there was
a greater incidence of adverse events considered to be related
to the study treatment among patients in Group B (11 adverse
events in Group A vs. 31 adverse events in Group B; χ2=
10,32; df= 2; p= 0.0057). No serious adverse events were
recorded during the treatment period.
There was no signicant change in the physical exam
and vital signs at Visit 2 and Visit 3 as compared to
pretreatment values in either patient group (p>0.05 for
Table 2 Demographic and Pretreatment Characteristics
Group A Group B Between-
Group
Difference
Gender (n) p= 0.317
Female 144 (100%) 143 (99.31%)
Male 0 (0%) 1 (0.35%)
Ethnicity (n) p = 0.28
Asian 3 (2.08%) 2 (1.39%)
Black 23 (15.97%) 21 (14.58%)
Caucasian 63 (43.75%) 79 (54.86%)
Mulatto 55 (38.19%) 42 (29.17%)
Age (years) 47.19 (±9.34) 44.21 (±11.46) p= 0.016
Weight (kg) 62.85 (±7.21) 62.01 (±6.97) p= 0.315
BMI (kg/cm
2
) 24.47 (±2.71) 24.15 (±2.45) p = 0.305
Blood pressure (mmHg)
Systolic 120.0 (±7.68) 120.4 (±8.94) p= 0.832
Diastolic 76.38 (±9.61) 78.38 (±9.42) p= 0.076
Heart rate (bpm) 69.69 (±6.18) 70.49 (±6.72) p= 0.295
Respiratory rate (ipm) 15.62 (±2.04) 15.95 (±1.80) p= 0.143
Cystitis duration (days) 6.35 (±2.56) 6.33 (±2.75) p= 0.947
Number of cystitis
episodes (last 6 months)
p= 0.387
2 104 (72.2%) 114 (79.2%)
3 35 (24.3%) 26 (18.1%)
4 5 (3.5%) 4 (2.8%)
Previous treatment with
antibiotics (n)
p= 0.143
Yes 117 (81.3%) 128 (89.9%)
No 6 (4.2%) 2 (1.4%)
Unsure 21 (15.6%) 14 (10.7%)
Previous treatment with
urinary antiseptics (n)
p= 0.878
Yes 72 (50.0%) 72 (50.0%)
No 42 (29.2%) 45 (31.3%)
Unsure 30 (20.8%) 27 (18.8%)
Note: Data are expressed as n(%) or mean and (±SD).
Abbreviations: bpm, beats per minute; cm, centimeter; ipm, inspiration
per minute; kg, kilogram; mmHg, millimeters of mercury.
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weight, BMI, blood pressure, heart rate, and respiratory
rate), and no between-group differences were observed at
Visit 2 or Visit 3 regarding these parameters.
Discussion
To our knowledge, this is the rst double-blind, randomized
study using a validated outcome measure to assess the efcacy
and safety of urinary antiseptics containing methenamine and
methylene blue in the treatment of cystitis. Previous studies on
the use of methenamine and methylene blue in cystitis have
focused primarily on prevention of recurrence, with favorable
results reported in otherwise healthy patients. Cronberg et al
(1987) reported superior prophylactic efcacy of methena-
mine over placebo, at the dose of 1g twice daily following
a 1-year randomized, double-blind, long-term, crossover study
with interchange between methenamine and placebo at 6
months.
18
Methenamine was superior to placebo in prevention
of recurrent UTIs in healthy pre- and postmenopausal women
over 6 and 12 months of treatment periods.
19–21
Use of methe-
namine hippurate was evaluated for UTI prevention in a 2002
Cochrane Review by Lee et al, and updated in 2004 and 2012.
The authors conclude that methenamine appears to be effec-
tive for UTI prevention in patients without renal tract abnorm-
alities, with a low rate of adverse effects. Following bacteriuria
resolution with antibiotic therapy, prophylactic administration
of methenamine could reduce the UTI re-incidence and con-
sequently the need for additional antibiotic therapy.
22
More
recently, a literature review by Chwa et al (2019) concluded
Table 3 UTISA Scores at Pretreatment (V1), Visit 2 (V2), and Visit 3 (V3), ITT Population
Treatment Group Visit Mean SD 95% CI Min Max Median Q1; Q3
Total UTISA Scores
Group A V1 19.0 6.2 [18.0; 20.0] 8 38 18 14.0; 23.0
V2 12.9 7.4 [11.7; 14.1] 0 42 13 8.0; 16.0
V3 0.76 2.2 [0.39; 1.1] 0 19 0 0.0; 0.0
Group B V1 17.8 6.6 [16.7; 18.9] 8 38 18 12.0; 22.0
V2 9.7 6.5 [8.6; 10.8] 0 30 8 4.0; 14.0
V3 0.85 1.6 [0.58; 1.1] 0 6 0 0.0; 1.5
UTISA Domain: Urination Regularity
Group A V1 7.7 2.6 [7.2; 8.1] 4 12 8 6.0; 10.0
V2 5.3 2.9 [4.8; 5.8] 0 12 6 0.0; 7.0
V3 0.3 0.9 [0.1; 0.4] 0 6 0 0.0; 0.0
Group B V1 7.0 2.5 [6.4; 7.3] 2 12 6.5 4.0; 8.0
V2 4.2 3.0 [3.7; 4.7] 0 12 4.0 2.0; 6.0
V3 0.2 0.7 [0.1; 0.4] 0 4 0 1.0; 0.0
UTISA Domain: Problems with Urination
Group A V1 6.7 2.6 [6.3; 7.1] 0 12 6 4.0; 8.0
V2 3.2 2.1 [2.9; 3.7] 0 9 3 2.0; 5.0
V3 0.3 0.9 [0.1; 0.4] 0 7 0 0.0; 0.0
Group B V1 6.6 2.6 [6.2; 7.1] 2 12 6 4.0; 8.0
V2 2.8 2.0 [2.4; 3.1] 0 9 3 2.0; 4.0
V3 0.5 1.2 [0.3; 0.7] 0 5 0 0.0; 0.0
UTISA Domain: Pain Associated with UTI
Group A V1 4.1 2.4 [3.7; 4.5] 0 12 4 2.0; 6.0
V2 2.6 2.0 [2.2; 2.9] 0 9 2 2.0; 4.0
V3 0.2 0.8 [0.1; 0.3] 0 6 0 0.0; 0.0
Group B V1 3.8 2.6 [3.3; 4.2] 0 12 4 2.0; 6.0
V2 1.6 1.9 [1.4; 2.0] 0 10 2 0.0; 2.0
V3 0.1 0.5 [0.0; 0.2] 0 3 0 0.0; 0.0
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that methenamine may be safe and effective for preventing
recurrent UTIs in adults aged 58 and older, including indivi-
duals submitted to genitourinary surgical procedures, and may
potentially benet patients in use of long-term
catheterization.
14
In 2008, Geller et al reported on the results of
a retrospective study assessing the use of the combination
of methenamine and methylene blue at the same concen-
trations used in the present study as prophylactics for
recurrent uncomplicated lower UTIs. Treatment periods
Figure 2 Evolution of UTISA domains (%) after 3 days of treatment with study medication (Visit 2) in relation to pretreatment scores.
Figure 3 Evolution of UTISA overall symptom severity evaluation at pretreatment (Visit 1), after 3 days of treatment with urinary antiseptics (Visit 2), and after 3 days of
treatment with urinary antiseptics + antibiotic (Visit 3).
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varied between 3–6 months, with daily oral doses of
methenamine ranging from 360–720mg and 60–120mg
of methylthioninium chloride. The authors reported signif-
icant reductions of UTI recurrence associated with treat-
ment using the combination of methenamine and
methylene blue.
23
Methenamine has also been reported to aid in preven-
tion of UTI recurrence among patients with related to co-
morbidities or following surgical procedures. Among
patients who underwent utero-vaginal prolapse surgery,
bacteriuria incidence was signicantly reduced with
prophylactic methenamine treatment.
24
Methenamine
together with acidication was reported to be superior to
placebo in preventing UTIs among patients with neuro-
genic bladder who underwent intermittent
catheterization.
25
Methenamine also reduced the incidence
of UTIs among patients with spinal cord injury-derived
neurogenic bladder.
26
When used prophylactically for pre-
vention of post-operative bacteriuria after gynecological
surgery, methenamine was reported to signicantly reduce
postoperative bacteriuria and UTIs.
27
Hydrolyzation of methenamine leads to formation of
ammonia and formaldehyde, which inhibits bacterial pro-
liferation and lacks bacterial resistance. Hamilton-Miller
and Brumtt (1977) reported a minimal inhibitory concen-
tration of formaldehyde of 13µg/mL. When in contact with
urinary pH of 5–6, methenamine may produce an antibac-
terial concentration of formaldehyde within 1 hour.
28
Urine containing 0.6–1mg/mL methenamine at pH ranging
from 5.7–5.85 reaches concentrations of formaldehyde
≥25µg/mL, and a measurable bacteriostatic effect is
observed after 2 hours.
29
Oral administration of 1g methe-
namine four times per day in healthy individuals was
associated with inhibition of urinary pathogen growth,
with urinary formaldehyde levels of 100–820mcg, free
formaldehyde of 3.2–16.6%, and urinary pH of 5.7–6.2.
30
The adverse events recorded during the treatment per-
iod were transitory and there were no serious adverse
events during the study. Previously reported adverse
events during treatment with the combination of methena-
mine and methylene blue included headache, diarrhea,
dyspepsia, epigastralgia, nausea, and cutaneous rash.
23,31
The combination of acriavine + methenamine + methy-
lene blue + Atropa belladonna L. may be associated with
decreased urine ow, gastrointestinal side effects including
nausea, vomiting, and diarrhea, as well as dry mouth,
dysphagia and speech difculties, decreased bronchial
secretion, pupil dilation, and skin redness and dryness.
There is also a risk for skin hypersensitivity reactions,
skin rash, eosinophilia, and anaphylaxis.
32
The efcacy of the two study treatment regimens was
equivalent in analysis of the primary and secondary end-
points. In the population evaluated in this study, the higher
dose of methenamine and co-administration of acriavine
and Atropa belladonna L. did not produce statistically
superior responses in patient or physician assessments
among the treated subjects. Both treatments
demonstrated efcacy in reducing the symptoms asso-
ciated with UTIs.
Table 4 Urine Culture and Bacterial Sensitivity Results
Bacterial Growth Antibiotic
Sensitivity
Group
A (n)
Group
B (n)
E. coli Ceftazidime 1 0
E. coli Cefuroxime 0 1
E. coli Ciprooxacin 133 128
E. coli Nitrofurantoin 1 0
E. faecalis Cefuroxime 0 1
Klebsiella Ciprooxacin 2 2
Klebsiella Gentamicin 1 0
Morganella Amikacin 0 1
Proteus Ampicillin 1 0
Proteus Ciprooxacin 0 1
Providência stuartii Trimethoprim/
sulfamethoxazole
1 0
Pseudomonas aeruginosa Amikacin 1 0
S. aureus Trimethoprim/
sulfamethoxazole
0 1
S. saprophyticus Ciprooxacin 2 9
Serratia marcescens Levooxacin 1 0
Table 5 Adverse Events by MedDRA System-Organ-Class
(SOC) at Visit 2
SOC Group
A (n)
Group
B (n)
Cardiac disorders 1 1
Gastrointestinal disorders 18 37
General disorders and administration site
conditions
1 0
Infections and infestations 1 0
Investigations 1 0
Metabolism and nutrition disorders 1 3
Nervous system disorders 3 5
Psychiatric disorders 0 2
Respiratory, thoracic and mediastinal
disorders
1 0
Skin and subcutaneous tissue disorders 0 3
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In light of the increasing concern over antibiotic resis-
tance, the results of this study support the suggestion that
the combination of methenamine and methylene blue may
be effective for symptomatic UTI relief while awaiting
urine culture and antibiotic sensitivity results, enabling
start of antibiotic treatment only after conrmed identi-
cation of bacterial species and most effective antibiotic on
an individual patient basis.
Conclusion
Both urinary antiseptic combinations were effective in
improving UTI symptoms, with comparable percentages
of subjects presenting improvements in cystitis manifesta-
tions on the UTISA domain “Urination Regularity” after 3
days of treatment (Visit 2). After 3 days of treatment,
signicant improvements in both treatment groups were
observed for total UTISA score and UTISA domain scores
“Problems with Urination” and “Pain Associated with
UTI,” and a comparable percentage of subjects had
improvement in UTISA question 9 (changes in UTI sever-
ity). The two treatments were also comparable in terms of
adverse event incidence, while patients treated with the
combination of methenamine and methylene blue pre-
sented fewer urinary antiseptic treatment-related adverse
effects, in the population evaluated in this study.
Data Sharing Statement
The authors agree to share study data upon request by
e-mail to the corresponding author, via e-mail (maurogel-
ler@gmail.com), to investigators whose proposed use of
the data has been approved by an independent review
committee or ethical committee and who agree to sign
a data access agreement. Data to be shared includes indi-
vidual deidentied participant data and study-related docu-
ments (i.e., study protocol, informed consent text, or other
study documentation requested), for a period of ve years
from the date of study publication.
Acknowledgments
The authors thank Silvia Maciel, Natalia Platenik, and
Thainá Zanon Cruz for study monitoring.
Disclosure
This study was sponsored by Laboratório Gross S.A. (Rio
de Janeiro, RJ, Brazil). The authors report no other con-
icts of interest in this work.
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