Flavoxate Hydrochloride

AHFS Class: Genitourinary Smooth Muscle Relaxants (86:12)

ATC Class: G04BD02
VA Class: GU201

View the associated Essentials monograph.

Introduction

Flavoxate hydrochloride, a derivative of flavone, is a genitourinary antispasmodic.

Uses

Flavoxate hydrochloride is used as an antispasmodic to provide symptomatic relief of dysuria, urgency, nocturia, suprapubic pain, frequency, and incontinence that may occur in patients with cystitis, prostatitis, urethritis, urethrocystitis, or urethrotrigonitis. Flavoxate therapy is not indicated as definitive treatment of these conditions but is compatible with drugs used for the treatment of urinary tract infections. Flavoxate has not been shown to be more effective in the treatment of these conditions than antimuscarinic agents.

Dosage and Administration

Administration

Flavoxate hydrochloride is administered orally.

Dosage

The usual dosage of flavoxate hydrochloride for patients older than 12 years of age is 100–200 mg 3 or 4 times daily. Dosage may be reduced as symptoms improve.

Cautions

Adverse Effects

Adverse effects of flavoxate hydrochloride include nausea and vomiting, dry mouth and throat, nervousness, vertigo, headache, drowsiness, blurred vision, increased ocular tension, disturbance in ocular accommodation, urticaria and other dermatoses, mental confusion (especially in geriatric patients), dysuria, tachycardia and palpitation, hyperpyrexia, and eosinophilia. Rarely, abdominal pain and difficulty in concentration may occur. Constipation has been reported in patients receiving 800 mg to 1.2 g of flavoxate hydrochloride daily. One case of leukopenia which was reversible following discontinuance of the drug has been reported.

Precautions and Contraindications

Because of possible drowsiness, vertigo, and ocular disturbances, flavoxate should be administered with caution to patients performing hazardous tasks requiring mental alertness or physical coordination. Flavoxate hydrochloride should also be administered with caution to patients with suspected glaucoma. The drug is contraindicated in patients with pyloric or duodenal obstruction, obstructive intestinal lesions or ileus, achalasia, GI hemorrhage, or obstructive uropathies of the lower urinary tract.

Pediatric Precautions

Safety and efficacy of flavoxate hydrochloride in children younger than 12 years of age have not been established.

Mutagenicity and Carcinogenicity

Studies to determine the mutagenic and carcinogenic potentials of flavoxate hydrochloride have not been performed.

Pregnancy, Fertility, and Lactation

Pregnancy

There are no well-controlled studies using flavoxate hydrochloride in pregnant women, and the drug should be used during pregnancy only when clearly needed.

Fertility

Reproduction studies in rats and rabbits using flavoxate hydrochloride doses up to 34 times the human dose have not revealed evidence of harm to the fetus or impaired fertility.

Lactation

Since it is not known whether flavoxate hydrochloride is distributed into milk, the drug should be used with caution in nursing women.

Pharmacology

Flavoxate hydrochloride exerts a direct spasmolytic (papaverine-like) action on smooth muscle. In vitro, the spasmolytic effect has been demonstrated on the small intestine, gallbladder, uterus, seminal vesicle, and colon of various animals. The peripheral dilator activity of the drug in animals is several times less than that of papaverine. Flavoxate hydrochloride has been reported to produce an increase in urinary bladder capacity in patients with evidence of bladder spasticity, possibly as a result of the action of the drug on the detrusor muscle. In animal studies, the drug was shown to have antihistaminic action. In contrast to papaverine, flavoxate also exhibited local anesthetic and analgesic action. The drug did not exhibit mydriatic or antisialagogue activity.

Pharmacokinetics

Based on animal studies, flavoxate hydrochloride appears to be well absorbed from the GI tract. In rats, peak plasma flavoxate concentrations were achieved approximately 2 hours following oral administration of the drug. In one study in healthy males, the onset of action was 55 minutes and the peak effect occurred at 112 minutes. It is not known whether the drug is distributed into milk. The manufacturer reports that 57% of a dose of flavoxate hydrochloride is excreted in urine within 24 hours after oral administration. It is not known whether the drug is dialyzable.

Chemistry and Stability

Chemistry

Flavoxate hydrochloride is a derivative of flavone. The drug occurs as an off-white powder and is freely soluble in water at 80°C and slightly soluble in alcohol at 18°C.

Stability

Flavoxate hydrochloride tablets should be stored at 15–30°C. The tablets have an expiration date of 3 years following the date of manufacture.

Preparations

Flavoxate Hydrochloride

Routes	Forms	Strengths	Brand Names	Manufacturer
Oral	Tablets, film-coated	100 mg*	Urispas®	Ortho-McNeil

* available by nonproprietary name

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. For the most current and up-to-date pricing information, please visit www.drugstore.com.

Urispas 100MG Tablets (MCNEIL): 28/$51.99 or 84/$132.97

Selected Revisions October 2007, © Copyright, October 1971, American Society of Health-System Pharmacists, Inc. 7272 Wisconsin Avenue, Bethesda, MD 20814.