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      Drugs & Diseases

      methenamine/hyoscyamine (Discontinued)

      Brand and Other Names:Prosed DS, Darpaz, more...Urogesic Blue
      • Print

      Dosing & Uses

      AdultPediatricGeriatric

      Dosage Forms & Strengths

      methenamine/hyoscyamine

      tablet

      • 81mg/0.12mg

      tablet, capsule

      • 120mg/0.12mg

      Urinary Tract Irritative Voiding Symptoms

      1 tablet/capsule PO q6hr with liberal fluid intake

      Use only after eradication of UTI by other appropriate antibiotic

      Methenamine: Indicated for prophylaxis/suppression for chronic recurring UTIs when long-term therapy is required

      Hyoscyamine: Adjunctive treatment for lower urinary tract hypermotility and spasm

      Dosage Forms & Strengths

      tablet

      • 81 mg/0.12mg

      tablet, capsule

      • 120 mg/0.12mg

      Urinary Tract Infection Prophylaxis

      <16 years: Safety/efficacy not established

      ≥16 years: 1 tablet/capsule PO q6hr with liberal fluid intake

      Use only after eradication of UTI by other appropriate antibiotic

      Methenamine: Indicated for prophylaxis/suppression for chronic recurring UTIs when long-term therapy is required

      Hyoscyamine: Adjunctive treatment for lower urinary tract hypermotility and spasm

      Avoid hyoscyamine except in short-term situations to decrease secretions; high incidence of anticholinergic effects (Beers criteria)

      Next:

      Interactions

      Interaction Checker

      and methenamine/hyoscyamine

      No Results

         activity indicator 
        No Interactions Found
        Interactions Found

        Contraindicated

          Serious - Use Alternative

            Significant - Monitor Closely

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                 activity indicator 

                Contraindicated (0)

                  Serious - Use Alternative (12)

                  • acetazolamide

                    acetazolamide, methenamine. Other (see comment). Contraindicated. Comment: This combination may form an insoluble precipitate in the urine, decreasing the effects of both agents.

                  • cholera vaccine

                    methenamine, cholera vaccine. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Avoid coadministration of cholera vaccine with systemic antibiotics since these agents may be active against the vaccine strain. Do not administer cholera vaccine to patients who have received oral or parenteral antibiotics within 14 days prior to vaccination.

                  • glucagon

                    glucagon increases toxicity of hyoscyamine by Other (see comment). Avoid or Use Alternate Drug. Comment: Coadministration of anticholinergic drugs and glucagon increase the risk of gastrointestinal adverse reactions due to additive effects on inhibition of gastrointestinal motility. .

                  • glucagon intranasal

                    glucagon intranasal increases toxicity of hyoscyamine by Other (see comment). Avoid or Use Alternate Drug. Comment: Coadministration of anticholinergic drugs and glucagon increase the risk of gastrointestinal adverse reactions due to additive effects on inhibition of gastrointestinal motility. .

                  • glycopyrronium tosylate topical

                    glycopyrronium tosylate topical, hyoscyamine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration of glycopyrronium tosylate topical with other anticholinergic medications may result in additive anticholinergic adverse effects.

                  • pramlintide

                    pramlintide, hyoscyamine. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Synergistic inhibition of GI motility.

                  • revefenacin

                    revefenacin and hyoscyamine both decrease cholinergic effects/transmission. Avoid or Use Alternate Drug. Coadministration may cause additive anticholinergic effects.

                  • secretin

                    hyoscyamine decreases effects of secretin by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Concomitant use of anticholinergic drugs may cause a hyporesponse to stimulation testing with secretin. Discontinue anticholinergic drugs at least 5 half-lives before administering secretin.

                  • sulfadiazine

                    methenamine, sulfadiazine. Other (see comment). Contraindicated. Comment: This combination may form an insoluble precipitate in the urine, decreasing the effects of both agents.

                  • sulfamethoxazole

                    methenamine, sulfamethoxazole. Other (see comment). Contraindicated. Comment: This combination may form an insoluble precipitate in the urine, decreasing the effects of both agents.

                  • sulfisoxazole

                    methenamine, sulfisoxazole. Other (see comment). Contraindicated. Comment: This combination may form an insoluble precipitate in the urine, decreasing the effects of both agents.

                  • umeclidinium bromide/vilanterol inhaled

                    hyoscyamine, umeclidinium bromide/vilanterol inhaled. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Concomitant use with other anticholinergic-containing drugs may lead to additive anticholinergic adverse effects.

                  Monitor Closely (85)

                  • abobotulinumtoxinA

                    abobotulinumtoxinA increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Use of anticholinergic drugs after administration of botulinum toxin-containing products may potentiate systemic anticholinergic effects. .

                  • aclidinium

                    hyoscyamine and aclidinium both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • amantadine

                    hyoscyamine, amantadine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Potential for increased anticholinergic adverse effects.

                  • amitriptyline

                    hyoscyamine and amitriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • amoxapine

                    hyoscyamine and amoxapine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • anticholinergic/sedative combos

                    anticholinergic/sedative combos and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • aripiprazole

                    hyoscyamine decreases levels of aripiprazole by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of aripiprazole by pharmacodynamic antagonism. Use Caution/Monitor.

                    aripiprazole increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • atracurium

                    atracurium and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • atropine

                    atropine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • atropine IV/IM

                    atropine IV/IM and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • belladonna alkaloids

                    belladonna alkaloids and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • belladonna and opium

                    hyoscyamine and belladonna and opium both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • benperidol

                    hyoscyamine decreases levels of benperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of benperidol by pharmacodynamic antagonism. Use Caution/Monitor.

                    benperidol increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • benztropine

                    benztropine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor. Additive anticholinergic adverse effects may be seen with concurrent use.

                  • bethanechol

                    bethanechol increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • buprenorphine, long-acting injection

                    buprenorphine, long-acting injection increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Coadministration of buprenorphine with anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus.

                  • carbachol

                    carbachol increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • cevimeline

                    cevimeline increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • chlorpromazine

                    hyoscyamine decreases levels of chlorpromazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of chlorpromazine by pharmacodynamic antagonism. Use Caution/Monitor.

                    chlorpromazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • cisatracurium

                    cisatracurium and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • clomipramine

                    hyoscyamine and clomipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • clozapine

                    hyoscyamine decreases levels of clozapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of clozapine by pharmacodynamic antagonism. Use Caution/Monitor.

                    clozapine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • cyclizine

                    cyclizine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • cyclobenzaprine

                    cyclobenzaprine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • darifenacin

                    darifenacin and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • desipramine

                    hyoscyamine and desipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • dicyclomine

                    dicyclomine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • diphenhydramine

                    diphenhydramine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • donepezil

                    donepezil increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • donepezil transdermal

                    donepezil transdermal, hyoscyamine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.

                  • dosulepin

                    hyoscyamine and dosulepin both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • doxepin

                    hyoscyamine and doxepin both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • droperidol

                    hyoscyamine decreases levels of droperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of droperidol by pharmacodynamic antagonism. Use Caution/Monitor.

                    droperidol increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • echothiophate iodide

                    echothiophate iodide increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • fesoterodine

                    fesoterodine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • flavoxate

                    flavoxate and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • fluphenazine

                    hyoscyamine decreases levels of fluphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of fluphenazine by pharmacodynamic antagonism. Use Caution/Monitor.

                    fluphenazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • galantamine

                    galantamine increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • glycopyrrolate

                    glycopyrrolate and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • glycopyrrolate inhaled

                    glycopyrrolate inhaled and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • haloperidol

                    hyoscyamine decreases levels of haloperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of haloperidol by pharmacodynamic antagonism. Use Caution/Monitor.

                    haloperidol increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • henbane

                    henbane and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • homatropine

                    homatropine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • huperzine A

                    huperzine A increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • iloperidone

                    hyoscyamine decreases levels of iloperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of iloperidone by pharmacodynamic antagonism. Use Caution/Monitor.

                    iloperidone increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • imipramine

                    hyoscyamine and imipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • ipratropium

                    hyoscyamine and ipratropium both decrease cholinergic effects/transmission. Use Caution/Monitor. Due to the poor systemic absorption of ipratropium, interaction unlikely at regularly recommended dosages.

                  • levodopa

                    hyoscyamine, levodopa. Other (see comment). Use Caution/Monitor. Comment: Anticholinergic agents may enhance the therapeutic effects of levodopa; however, anticholinergic agents can exacerbate tardive dyskinesia. In high dosage, anticholinergics may decrease the effects of levodopa by delaying its GI absorption. .

                  • lofepramine

                    hyoscyamine and lofepramine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • loxapine

                    hyoscyamine decreases levels of loxapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of loxapine by pharmacodynamic antagonism. Use Caution/Monitor.

                    loxapine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • loxapine inhaled

                    loxapine inhaled increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                    hyoscyamine decreases levels of loxapine inhaled by pharmacodynamic antagonism. Use Caution/Monitor.

                  • maprotiline

                    hyoscyamine and maprotiline both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • meclizine

                    hyoscyamine and meclizine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • methscopolamine

                    hyoscyamine and methscopolamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • metoclopramide intranasal

                    hyoscyamine will decrease the level or effect of metoclopramide intranasal by Other (see comment). Use Caution/Monitor. Coadministration of metoclopramide intranasal with drugs that impair GI motility may decrease systemic absorption of metoclopramide. Monitor for reduced therapeutic effect.

                  • neostigmine

                    neostigmine increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • nortriptyline

                    hyoscyamine and nortriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • olanzapine

                    hyoscyamine decreases levels of olanzapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of olanzapine by pharmacodynamic antagonism. Use Caution/Monitor.

                    olanzapine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • oliceridine

                    hyoscyamine increases toxicity of oliceridine by Other (see comment). Use Caution/Monitor. Comment: Anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Monitor for signs of urinary retention or reduced gastric motility if oliceridine is coadministered with anticholinergics.

                  • onabotulinumtoxinA

                    onabotulinumtoxinA and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • orphenadrine

                    hyoscyamine and orphenadrine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • oxybutynin

                    hyoscyamine and oxybutynin both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • oxybutynin topical

                    hyoscyamine and oxybutynin topical both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • oxybutynin transdermal

                    hyoscyamine and oxybutynin transdermal both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • paliperidone

                    hyoscyamine decreases levels of paliperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of paliperidone by pharmacodynamic antagonism. Use Caution/Monitor.

                    paliperidone increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • pancuronium

                    hyoscyamine and pancuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • perphenazine

                    hyoscyamine decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor.

                    perphenazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • physostigmine

                    physostigmine increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • pilocarpine

                    pilocarpine increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • pimozide

                    hyoscyamine decreases levels of pimozide by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of pimozide by pharmacodynamic antagonism. Use Caution/Monitor.

                    pimozide increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • prabotulinumtoxinA

                    hyoscyamine, prabotulinumtoxinA. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Use of anticholinergic drugs after administration of botulinum toxin-containing products may potentiate systemic anticholinergic effects.

                  • pralidoxime

                    hyoscyamine and pralidoxime both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • prochlorperazine

                    hyoscyamine decreases levels of prochlorperazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of prochlorperazine by pharmacodynamic antagonism. Use Caution/Monitor.

                    prochlorperazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • promethazine

                    hyoscyamine decreases levels of promethazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of promethazine by pharmacodynamic antagonism. Use Caution/Monitor.

                    promethazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • propantheline

                    hyoscyamine and propantheline both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • protriptyline

                    hyoscyamine and protriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • pseudoephedrine

                    methenamine decreases effects of pseudoephedrine by unknown mechanism. Use Caution/Monitor. Urinary excretion of indirect acting alpha/beta agonists (eg, pseudoephedrine) may increase when administered concomitantly with urinary acidifying agents, resulting in lower serum concentrations.

                  • pyridostigmine

                    pyridostigmine increases and hyoscyamine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.

                  • quetiapine

                    hyoscyamine decreases levels of quetiapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of quetiapine by pharmacodynamic antagonism. Use Caution/Monitor.

                    quetiapine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • rapacuronium

                    hyoscyamine and rapacuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • risperidone

                    hyoscyamine decreases levels of risperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.

                    hyoscyamine decreases levels of risperidone by pharmacodynamic antagonism. Use Caution/Monitor.

                    risperidone increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

                  • rocuronium

                    hyoscyamine and rocuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • scopolamine

                    hyoscyamine and scopolamine both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  • sodium picosulfate/magnesium oxide/anhydrous citric acid

                    methenamine decreases effects of sodium picosulfate/magnesium oxide/anhydrous citric acid by altering metabolism. Use Caution/Monitor. Coadministration with antibiotics decreases efficacy by altering colonic bacterial flora needed to convert sodium picosulfate to active drug.

                  • solifenacin

                    hyoscyamine and solifenacin both decrease cholinergic effects/transmission. Use Caution/Monitor.

                  Minor (3)

                  • dimenhydrinate

                    dimenhydrinate increases toxicity of hyoscyamine by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

                  • donepezil

                    donepezil decreases effects of hyoscyamine by pharmacodynamic antagonism. Minor/Significance Unknown.

                  • galantamine

                    galantamine decreases effects of hyoscyamine by pharmacodynamic antagonism. Minor/Significance Unknown.

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                  Adverse Effects

                  >10%

                  Hyoscyamine

                  • Dry skin

                  1-10%

                  Methenamine

                  • Dysuria
                  • Discoloration of urine (blue)
                  • Gastric upset
                  • Nausea
                  • Rash

                  Hyoscyamine

                  • Blurred vision
                  • Constipation
                  • Dysphagia
                  • Photosensitivity

                  <1%

                  Hyoscyamine

                  • Headache
                  • Orthostatic hypotension
                  • Tachycardia
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                  Warnings

                  Contraindications

                  Methenamine

                  • Hypersensitivity to methenamine or tartrazine (FD&C Yellow No. 5)
                  • Renal or severe hepatic insufficiency
                  • Concurrent sulfonamides or acetazolamide may form insoluble precipitate in urine

                  Hyoscyamine

                  • Hypersensitivity to hyoscyamine or related compounds
                  • Closed-angle glaucoma, myasthenia gravis, hemorrhage w/ cardiovascular instability, paralytic ileus, intestinal atony of elderly/debilitated pt, obstructive uropathy, toxic megacolon, GI obstruction, tachycardia secondary to cardiac insufficiency or thyrotoxicosis
                  • Breastfeeding

                  Cautions

                  Methenamine

                  • Large doses may cause bladder irritation, urinary frequency, albuminuria, and hematuria
                  • Maintain acidic pH of urine, esp. when treating urea-splitting organisms (eg, Proteus, Pseudomonas)
                  • Monitor LFTs, especially with history of liver impairment
                  • Safe use not established during pregnancy, especially 1st and 2nd trimester
                  • May precipitate uric acid stones in patients with gout

                  Hyoscyamine

                  • Renal/hepatic impairment, BPH, CHF, CAD, HTN, COPD, hiatal hernia, reflux esophagitis, mitral stenosis, brain damage or spastic paralysis in children, salivary secretion disorder, Down syndrome, autonomic neuropathy, hyperthyroidism, tachyarrythmia, toxin-mediated diarrhea
                  • Elderly
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                  Pregnancy & Lactation

                  Pregnancy Category: C

                  Lactation: hyoscyamine and methenamine excreted in human milk; caution in breastfeeding women

                  Pregnancy Categories

                  A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

                  B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

                  C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

                  D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

                  X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

                  NA: Information not available.

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                  Pharmacology

                  Mechanism of Action

                  Methenamine: Hydrolyzed in acidic urine to ammonia and formaldehyde, which are bactericidal agents; does not convert to formaldehyde in serum

                  Hyoscyamine: Elicits anticholinergic activity; decreases urinary spasms with cystitis

                  Additional ingredients in some products: Methylene blue (weak antiseptic properties); sodium phosphate monobasic (acidifier); phenyl salicylate (mild analgesic)

                  Absorption

                  Well absorbed; 10-30% hydrolyzed by gastric acid unless enteric coated tablet

                  Peak Urine Time: (formaldehyde) 2 hr for hippurate salt, 3-8 hr for mandelate salt

                  Metabolism

                  Liver (10-25%)

                  Elimination

                  Half-Life: 3-6 hr

                  Excretion: urine (90%)

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                  Images

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                  Patient Handout

                  A Patient Handout is not currently available for this monograph.
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                  Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.
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