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Generic name: hyoscyamine sulfate, methenamine, phenyl salicylate, sodium phosphate, monobasic, monohydrate and methylene blue
Dosage form: capsule
Drug class: Urinary antispasmodics

Medically reviewed by Last updated on Nov 23, 2020.

Disclaimer: This drug has not been found by FDA to be safe and effective, and this labeling has not been approved by FDA. For further information about unapproved drugs, click here.

Phosenamine Description

Each capsule for oral administration contains:
Hyoscyamine Sulfate .12 mg
Methenamine 120 mg
Phenyl Salicylate 36 mg
Sodium Phosphate Monobasic 40.8 mg
Methylene Blue 10 mg

Inactive Ingredients: Dicalcium Phosphate, FD&C Blue #1, FD&C Red #3, Gelatin, Magnesium Stearate, Microcrystalline Cellulose, Silicon Dioxide, Stearic Acid, Titanium Dioxide, Shellac, Propylene Glycol, Sodium Hydroxide, Povidone.

Indications and Usage for Phosenamine

Phosenamine is indicated for the relief of discomfort of the urinary tract resulting from irritative voiding, diagnostic procedures, hypermotility, inflammation, and/or certain types of lower urinary tract infections.

Phosenamine Dosage and Administration

Adults: One capsule 4 times per day by mouth, followed by liberal fluid intake.
Older Children: Dosage must be individualized by physician.
Not recommended for use in children younger than six years.


Phosenamine is contraindicated in patients hypersensitive to any of its ingredients. Risk benefits should be carefully considered when the following medical problems exist: achalasia of esophagus, atony of colon, diseases of cardiovascular system, gastrointestinal hemorrhage; claucoma; hemolytic anemia from pyruvate kinase and G6PD deficiencies, infected urolithiasis, myasthenia gravis, paralytic ileus, severe ulcerative colitis, toxic megacolon; acute urinary retention may be precipitated in obstructive uropathy (such as bladder neck obstruction due to prostatic hypertrophy).

Warnings and Precautions

Do not exceed recommended dosage. This drug may make you dizzy or drowsy or cause blurred vision; use caution while driving, using machinery, or doing any activity that requires alertness or clear vision. Limit alcohol consumption. Cross sensitivity and/or related problems: Patients intolerant of other belladonna alkaloids or other salicylates may be intolerant of this medication also. Delay in gastric emptying could complicate the management of gastric ulcers. There have been no studies to establish the safety or prolonged use of this product in humans. No known long-term animal studies have been performed to evaluate carcinogenic potential.

Pregnancy: Teratogenic Effects. Pregnancy Category C: Hyoscyamine Sulfate and Methenamine cross the placenta. Studies have not been done in animals or humans. It is not known whether Phosenamine capsules cause fetal harm when administered to a pregnant woman or can affect reproduction. Phosenamine capsules should be given to a pregnant woman only if clearly needed.

Nursing Mothers: Problems in humans have not been documented; however, Methenamine and traces of Hyoscyamine Sulfate are excreted in breast milk.
Phosenamine capsules should be given to a lactating woman only if clearly needed.
Discuss the risks and benefits with your doctor.

Pediatric Use: Infants and young children are especially susceptible to the toxic effect of the belladonna alkaloids (Hyoscyamine Sulfate). This product contains salicylate, which is related to aspirin. Children and teenagers should not take aspirin, aspirin-containing or aspirin-related medications if they have chickenpox, influenza, or any undiagnosed illness without first consulting a doctor. A rare but serious illness known as Reye’s syndrome may occur. This medication is not recommended for children younger than 6 years.

Geriatric Use: Use with caution in elderly patients as they may respond to usual doses of Hyoscyamine Sulfate excitement, agitation, drowsiness or confusion.

Adverse Reactions

Cardiovascular: rapid heartbeat, flushing
Central Nervous System: blurred vision dizziness, drowsiness
Genitourinary: difficulty urinating, acute urinary retention
Gastrointestinal: dry mouth, nausea and vomiting
Respiratory: shortness of breath or trouble breathing

Serious allergic reactions to this drug are rare. Seek immediate medical attention if you notice symptoms of a serious allergic reaction, including itching rash, severe dizziness, swelling or trouble breathing.

This medication can cause urine and sometimes stools to turn blue-green. This effect is harmless and will subside after medication is stopped.

Call your doctor or physician for medical advice about side effects. The following number does not provide medical advice, but in the U.S. you may report suspected side effects to the FDA at 1-800-FDA-1088.

Drug Interactions

This drug should not be used with the following medications because very serious interactions may occur: live influenza virus vaccine, pramlintide. Because of this product’s effect on gastrointestinal motaility and gastric empyting, it may decrease the absorption of other oral medications during concurrent use such as: urningary alkalizers; thiazide diuretics (may cause the urine to become alkaline reducing the effectiveness of Methanamine by inhibiting its conversion to formaldehyde); antimuscarinics (concurrent use may intensify antimuscarinic effects of Hyosaymine Sulfate because of secondary antimuscarinic activities of these medications); antacids/antidiarrheals (may reduce absorption of Hyoscymine Sulfate, concurrent use with antacids may cause urine to become alkaline reducing effectiveness of Methenamine by inhibiting its concersion to formaldehyde. Doses of these medications should be spaced 1 hour apart from doses of Hyoscymine Sulfate; antimyasthenics (concurrent use with Hyoscyamine Sulfate may further reduce intestinal motility); ketoconazole); monoamine oxidase (MAO) inhibitors (concurrent use may intensify antimuscarinic side effects), opioid (narcotic analgesics may result in increased risk of severe constipation); sulfonamides (these drugs may precipitate with formaldehyde in the urine, increasing the danger of crystalluria). This is not a complete list of all drug interactions. Tell your doctor or pharmacist of all prescription medications prior to use.

Drug Abuse and Dependence

A dependence on the use of Phosenamine has not been reported nor expected based on the pharmacology of the ingredients contained in Phosenamine.


By exceeding the recommended dosage of Phosenamine, symptoms related to the overdose most probably be manifested in the symptoms related to overdose of its individual active ingredients may be expected as follows:

Hyoscyamine Sulfate: Symptoms associated with overdosage of Phosenamine will most probably be manifested in the symptoms related to overdosage of alkaloid Hyoscyamine Sulfate. Such symptoms as dryness of mucous membranes; dilation of pupils, hot, dry, flushed skin; hyperpyrexia, tachycardia, palpitations; elevated blood pressure, coma; circulatory collapse and death from respiratory failure can occur due to overdosage of these alkaloids.

Methenamine: If large amounts of the drug (2-8g daily) are used over extended periods (3-4 weeks), bladder and gastrointestinal irritation, painful and frequent urination, albuminuria and gross hematuria may be expected.

Phenyl Slicylate: Symptoms of Phenyl Salicylate overdosage include burning pain in throat and mouth, white necrotic lesions in the mouth, abdominal pain, vomiting, bloody diarrhea, pallor, sweating, weakness, headache, dizziness and tinnitus. The symptoms, however, are not expected to be discernible from those associated with the other active ingredients in Phosenamine.

Sodium Phosphate Monobasic: Symptoms of Sodium Biphosphate overdosage may include diarrhea, dehydration, and electrolyte imbalances.

Methylene Blue: Symptoms of Methylene Blue overdosage associated with the overdosage of Phosenamine are not expected to be discernible from those associated with other active ingredients in Phosenamine.

Treatment: Emesis or gastric lavage. Slow intravenous administration of physostigmine in doses of 1 to 4 mg (0.5 to 1 mg in children), repeated as needed in one to two hours to reverse severe antimuscarinic symptoms.
Administration of small doses of diazepam or baclofen to control excitement and seizures. Artificial respiration with oxygen if needed for respiratory depression. Adequate re-hydration is required. Symptomatic treatment as determined by a doctor.

If overdose is suspected, contact your local poison center or emergency room immediately. US residents can contact the US National Poison Hotline at 1-800-222-1222.

Phosenamine - Clinical Pharmacology

Hyoscyamine Sulfate:
Hyoscyamine Sulfate is parasympatholytic drug which relaxes smooth muscles. Protein binding for Hyoscyamine sulfate is moderate. Biotransformation for Hyoscyamine sulfate is hepatic. It is well absorbed from the gastrointestinal tract. The majority of Hyoscyamine sulfate is excreted unchanged.

Methenamine, after oral administration, undergoes hydrolysis and generates formaldehyde, which provides bactericidal or bacteriostatic action. Methenamine is rapidly absorbed from the intestinal tract and is excreted, for the most part, unchanged in the urine at which point it is hydrolyzed if the urine is acidic. It is almost completely excreted (90%) in the urine within 24 hours; of this at a ph of 5, approximately 10-30% is converted to formaldehyde in the stomach.

Phenyl Salicylate:
Phenyl Salicylate, a form of salicylic acid, is a mild analgesic for pain relief.

Sodium Phosephate, Monobasic:
Sodium Phosephate, Monobasic increases urinary acidity helping to maintain an acid pH necessary for the degradation of methenamine.

Methylene Blue:
Methylene Blue is monoamine oxidase inhibitor with weak antiseptic properties. It is well absorbed by the intestinal tract and rapidly reduced to leukomethylene blue, which is stabilized in the urine. Approximately 70-80% is excreted unchanged in the urine.

How is Phosenamine Supplied

Phosenamine is available as a purple capsule imprinted “RE 293” bottles of 100 capsules, NDC 68032-293-10. Dispense in a tight, light-resistant container as defined in the USP/NF with a child resistant closure. Store at controlled room temperature 15-30C (59-86F). Keep in a cool, dry place.
WARNING: Keep this and all drugs out of reach of children.
Caution: Rx Only


Sample packaging:

hyoscyamine sulfate, methenamine, phenyl salicylate, sodium phosphate, monobasic, monohydrate, methylene blue capsule
Product Information
Product Type HUMAN PRESCRIPTION DRUG LABEL Item Code (Source) NDC:68032-293
Route of Administration ORAL DEA Schedule
Active Ingredient/Active Moiety
Ingredient Name Basis of Strength Strength
Inactive Ingredients
Ingredient Name Strength
Product Characteristics
Color purple Score no score
Shape CAPSULE Size 15mm
Flavor Imprint Code RE;293
# Item Code Package Description
1 NDC:68032-293-10 100 CAPSULE (CAPSULE) in 1 BOTTLE
Marketing Information
Marketing Category Application Number or Monograph Citation Marketing Start Date Marketing End Date
unapproved drug other 01/01/2009 03/31/2011
Labeler - River's Edge Pharmaceuticals, LLC (133879135)
River's Edge Pharmaceuticals, LLC

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