Questions about Atrial Fibrillation? Get answers from our expert.

Isoxsuprine (Systemic)


VA CLASSIFICATION
Primary: CV500
Secondary: GU900

Commonly used brand name(s): Vasodilan.

Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).



Category:


Vasospastic therapy adjunct—

senility symptoms treatment adjunct—

labor (premature) inhibitor—

antidysmenorrheal—

Indications

Note: Bracketed information in the Indications section refers to uses that are not included in U.S. product labeling.

Accepted

Cerebrovascular insufficiency (treatment) or
Vascular disease, peripheral (treatment)1—FDA has classified isoxsuprine as being possibly effective for its labeled indications, which include relief of symptoms associated with cerebrovascular insufficiency and peripheral vascular disease, i.e., arteriosclerosis obliterans, thromboangiitis obliterans (Buerger's disease), and Raynaud's disease. This classification requires the submission of adequate and well-controlled studies in order to provide substantial evidence of effectiveness.

[Labor, premature (prophylaxis and treatment)]—Isoxsuprine is also used for management of threatened premature labor in pregnancies of 20 or more weeks' gestation. Use is not recommended prior to the 20th week of pregnancy. In order for isoxsuprine to be most effective, it is recommended that therapy be started as soon as the diagnosis of preterm labor is confirmed. Efficacy in advanced labor has not been established. Use in patients with ruptured membranes must be weighed against the risk of intrauterine infection.

[Dysmenorrhea (treatment)]1—Isoxsuprine has been used in the treatment of dysmenorrhea.

1 Not included in Canadian product labeling.



Pharmacology/Pharmacokinetics

Physicochemical characteristics:
Molecular weight—
    337.85

Mechanism of action/Effect:

Vasospastic therapy adjunct and senility symptoms treatment adjunct—Isoxsuprine produces peripheral vasodilation by a direct effect on vascular smooth muscle, primarily within skeletal muscle with little effect on cutaneous blood flow. Its effects were once thought to be due to beta-adrenergic receptor stimulation but are not reversed by beta-adrenergic blocking agents.

Labor (premature) inhibitor and antidysmenorrheal—Isoxsuprine produces uterine relaxation through a direct effect on smooth muscles {02}.


Other actions/effects:

Isoxsuprine-induced cardiac stimulation leads to increases in heart rate and cardiac output.

Isoxsuprine-induced peripheral vasodilation leads to decreased peripheral vascular resistance.

Absorption:

Isoxsuprine is well absorbed from the gastrointestinal tract.

Biotransformation:

Partially conjugated in the blood.

Half-life:


Adults:

Approximately 1.25 hours.



Neonates (following maternal administration [to inhibit premature labor]):

Near term: 1.5 to 3 hours.

Less mature: 6 to 8 hours.


Onset of action:

Oral—1 hour.

Intravenous—10 minutes.

Elimination:
    Primarily in the urine; fecal excretion insignificant.


Precautions to Consider

Pregnancy/Reproduction

Pregnancy—
Isoxsuprine crosses the placenta. Maternal isoxsuprine administration for prevention of premature labor has been associated with tachycardia, hypoglycemia, hypocalcemia, ileus, and hypotension in the neonate. Incidence of toxicity is related directly to neonatal blood concentrations of isoxsuprine, which are affected by both gestational age and the interval between administration of isoxsuprine and delivery (with regard to rate of elimination of the drug).

Breast-feeding

Problems in humans have not been documented.

Geriatrics


No information is available on the relationship of age to the effects of isoxsuprine in geriatric patients. However, the risk of isoxsuprine-induced hypothermia may be increased in elderly patients.

Drug interactions and/or related problems
The following drug interactions and/or related problems have been selected on the basis of their potential clinical significance (possible mechanism in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):

Smoking, tobacco    (concurrent heavy use may interfere with the therapeutic effects of isoxsuprine because nicotine constricts blood vessels)



Laboratory value alterations
The following have been selected on the basis of their potential clinical significance (possible effect in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):

With physiology/laboratory test values
Free fatty acids, serum and
Glucose, blood and
Insulin, serum    (concentrations may be transiently increased during intravenous infusion but usually return to pretreatment values within 24 to 72 hours, even with continued infusion)


Potassium, serum    (concentrations may be decreased during intravenous infusion; related to changes in glucose and insulin)


Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).


Except under special circumstances, this medication should not be used immediately postpartum or when the following medical problems exist:

For use in management of premature labor only:
» Cardiac disorders, especially those associated with arrhythmias, or
» Hyperthyroidism, maternal{02}    (isoxsuprine may precipitate arrhythmias or heart failure; occult cardiac disease may be unmasked)


» Chorioamnionitis (intrauterine infection) or
» Hemorrhage or
» Intrauterine fetal death or known abnormality{02}    (immediate delivery required)


» Eclampsia (toxemia) and severe pre-eclampsia{02}
» Pulmonary hypertension{02}
Risk-benefit should be considered when the following medical problems exist

For all indications:
Bleeding disorders
» Cerebrovascular disease, severe, or
Myocardial infarction, recent, or
» Obliterative coronary artery disease, severe    (a ``steal effect'' may occur, since isoxsuprine has a greater effect on peripheral than on cerebral and coronary vessels, leading to a further decrease in flow to ischemic areas)


Glaucoma
» Hypotension—for parenteral administration only; intravenous administration not recommended
Sensitivity to isoxsuprine
» Tachycardia—for parenteral administration only; intravenous administration not recommended
For use in management of premature labor only (in addition to the above):
Asthma being treated with beta-adrenergic stimulants and/or steroids
» Diabetes mellitus{02}    (may be aggravated)


Hypertension
» Pre-eclampsia, mild to moderate

Patient monitoring
The following may be especially important in patient monitoring (other tests may be warranted in some patients, depending on condition; » = major clinical significance):


For all indications
Blood pressure measurement in lying, sitting, and standing positions    (recommended at periodic intervals to detect hypotension in patients receiving isoxsuprine)


For use in premature labor only
» Blood glucose concentrations and
» Fluid and electrolyte status    (should be monitored carefully during prolonged intravenous administration, especially in diabetic patients or those receiving adrenocorticoids, potassium-depleting diuretics, or digitalis glycosides)


Fetal heart rate and
Maternal heart rate and blood pressure and
Uterine activity    (should be monitored frequently during intravenous administration)




Side/Adverse Effects

Note: A potentially serious maternal pulmonary edema has occurred with intravenous administration of isoxsuprine for premature labor. Although the exact cause is unknown, it may be related to fluid overload and has sometimes occurred with concurrent corticosteroid administration.

The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:

Those indicating need for medical attention
Incidence rare
    
Allergic reaction (skin rash)
    
chest pain
    
hypotension (dizziness; fainting)—low blood pressure
    
pulmonary edema (shortness of breath)
    
tachycardia (fast heartbeat)

Note: Incidence of hypotension and tachycardia may be increased with higher doses and with parenteral administration, and may occur in both mother and baby during use for delay of premature labor.




Those indicating need for medical attention only if they continue or are bothersome
Incidence less frequent
    
Nausea or vomiting

Note: Nausea or vomiting may occur more frequently with parenteral administration.






Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Isoxsuprine (Systemic).

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):

Before using this medication
»   Conditions affecting use, especially:
Sensitivity to isoxsuprine

Pregnancy—Risk of tachycardia, hypoglycemia, hypocalcemia, ileus, and hypotension in the neonate





Use in the elderly—Increased risk of isoxsuprine-induced hypothermia
Other medical problems, especially cerebrovascular disease, coronary artery disease, diabetes mellitus (for use in premature labor), hyperthyroidism (for use in premature labor), or other cardiac disease (for use in premature labor)

Proper use of this medication
» Taking with meals, milk, or antacids to reduce gastrointestinal irritation

» Proper dosing
Missed dose: Taking as soon as possible; not taking if almost time for next dose; not doubling doses

» Proper storage

Precautions while using this medication
Checking with physician before discontinuing medication since it may take some time to work

Avoiding smoking (nicotine constricts blood vessels)

» Caution when getting up from a lying or sitting position, when climbing stairs, or if dizziness occurs

For use in premature labor
» Checking with physician immediately if contractions begin again or water breaks


Side/adverse effects
Signs of potential side effects, especially allergic reaction, chest pain, pulmonary edema, hypotension, and tachycardia


General Dosing Information
It is recommended that isoxsuprine therapy be discontinued if skin rash occurs.

Isoxsuprine may be administered with meals, milk, or antacids to reduce gastrointestinal irritation.

For use in premature labor
For inhibition of premature labor, isoxsuprine has been administered by intravenous infusion at an initial rate of 200 mcg (0.2 mg) to 1 mg per minute followed by 100 to 300 mcg (0.1 to 0.3 mg) per minute until 1 to 1.5 hours after contractions have been abolished. This is usually followed by oral administration of 5 to 20 mg every 3 to 6 hours until term.

In order to prevent toxicity in the neonate, isoxsuprine should be discontinued when it becomes apparent that delivery is imminent.


Oral Dosage Forms

ISOXSUPRINE HYDROCHLORIDE TABLETS USP

Usual adult dose
Vasospastic therapy adjunct
Oral, 10 to 20 mg three or four times a day.


Strength(s) usually available
U.S.—


10 mg (Rx) [Vasodilan][Generic]


20 mg (Rx) [Vasodilan][Generic]

Canada—


10 mg (Rx) [Vasodilan]


20 mg (Rx) [Vasodilan]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a tight container.



Parenteral Dosage Forms

ISOXSUPRINE HYDROCHLORIDE INJECTION USP

Usual adult dose
Labor (premature) inhibitor
Intramuscular, 5 to 10 mg two or three times a day.


Usual adult prescribing limits
Because of the risk of hypotension and tachycardia, single intramuscular doses greater than 10 mg are not recommended, although repeated administration of 5 to 10 mg at suitable intervals is considered acceptable.

Strength(s) usually available
U.S.—
Not commercially available.

Canada—


5 mg per mL (Rx) [Vasodilan]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Protect from freezing.

Preparation of dosage form:
An intravenous infusion is prepared by dilution of the injection in an appropriate quantity of 5% dextrose injection, 5% dextrose in 0.45% sodium chloride injection, or 5% dextrose in 0.23% sodium chloride injection. Dilution in 0.9% sodium chloride injection is not recommended because of the risk of pulmonary edema.



Revised: 07/15/1994



References

Note: All references used in the development and earlier revisions of this monograph have not yet been incorporated into the computer database and, therefore, are not listed below. Citations for information not yet referenced in the monograph will be provided upon request.

  1. Vasodilan package insert (Mead Johnson—US), Rev 2/91, Rec 4/92.
  1. Vasodilan product information (Bristol—Canada), Rev 10/81, Rec 4/92.
  1. Caritis SN, Edelstone DI, Mueller-Heubach E. Pharmacologic inhibition of preterm labor. Am J Obstet Gynecol 1979; 133: 557-78.

Questions about Atrial Fibrillation? Get answers from our expert. Watch Video

Close
Hide
(web5)