Interacting drugs - summary
             
Metaraminol +

Guanethidine

 antihypertensive effects of guanethidine may be partially or totally
 reversed by the mixed-acting sympathomimetics

+Metaraminol

Digitalis  glycosides

 use metaraminol with caution in digitalised patients, because
 the combination of digitalis and sympathomimetics amines may
 cause etopic arrhythmias

Halogenated hydrocarbon anesthetics

halogenated hydrocarbon anesthetics may sensitise the effects of
catecholamines. Use of vasopressors may lead to serious  
arrthythmias, use with extreme caution

Monoamine oxidase inhibitors    

MAOIs increase the pressor response to mixed-acting vasopresors. Possible hypertensive crisis and intracranial  hemorrhage may occur. This interaction may also occur with
 furazolidone, an antimicrobial with MAOI activity. Avoid this combination                                                          

Oxytocic drugs 

 if vasopressor drugs are used in obstertics to correct hyoptension
 or added to local anesthetic solution, some oxytocic drugs may
 cause severe persistent hypertension

Tricyclic antidepressants

 the vasopressor response of the mixed-acting vasopressors may
 be  decreased by tricyclic antidepressants, a higher dose of the
 sympathomimetic may be necessary


 

Acute hypotensive states

VASSOPRESSORS USED IN SHOCK-  include-

Inotropic effects -
Isoproternol, Dobutamine, Dopamine, Ephinephrine,

Mixed  effects-
Norephinephrine, Ephedrine, Mephentermine

Pressors effects-
Metaraminol
Methoxamine
Phenylephrine


 

Cardiovascular- Sympathomimetics amines may cause sinus or ventricular tachycardia or arrhythmias,  especially in patients with MI. Hypertension, hypotension following cessation of the drug  cardiac arrhythmias, cardiac arrest and palpitations have occured.

Miscellaneous- Headache, flushing, sweating, tremors, dizziness, nausea, apprenhension, abcess  formation, tissue necrosis., sloughing at injection site.

 

Use with cyclopropane or halothane anesthesia, unless clinical circumstances demand such use.

Special precautions:
Use with caution in heart and thyroid disease, hypertension or diabetes.

Hypovolemia- not a substitute for replacement of blood, plasma, fluids, and electrolytes, which
should be restored promptly when l0ss has occured.

Vasoconstriction- may prevent expansion of circulating volume andmay perputuate the shock state.
Therefore, employ blood or plasma volume expanders when circulating volume is decreased

Hypertension- avoid excessive blood pressure response.  

Cirrhosis-  treat patients cautiousl and with adequate restoration of electrolyes if diuresis ensures.

Cumulative effects- because of its prolonged action, a cummulative effect is possible. It is important to make frequent assesesment of the blood pressure, particularly when administering IV.

Extravasation- excercise care when selecting the site of administration of this drud, particularly  when giving by the IV route.

Malaria- sympathomimetic amines may provoke a relapse in patients with a history of malaria.

Warnings-

Cardiac effects- metaraminol may cause cardiac arrhythmias. This may be particularly dangerous  in patients with myocardial infarction or in patients who have received anesthetics which sensitize  the heart to catecholamines ie cyclopropane,halothane

Pregnancy- give metaraminol to a pregnant woman only if clearly needed.

Lactation- excercisecaution when giving metaraminol to a nursing woman.

Children- safety and effectiveness in children have not been established.

Indications:
Acute hypotensive states

Dosage:
May be given IM,Sc or IV-  recommended dose is 2 to 10mg.

Overdosage-  Symptoms                                                               

Overdosage with metaraminol may cause convulsions, severe hypertension, headache, constricting sensation in the chest, nausea, vomiting, euphoria, disphoresis, pulmonary edema, tachycardia, bradycardia, sinus arrhythmia artial or ventricular arrhythmias, myocardial infarction, cardiac arrest, cerebral hemorrhage or cardiac arrhythmias
Patients with hyperthyroidism or hypertension are particularly sensitive to these effects.  
                      

Treatment

1. An appropiate antiarrhythmic agent may be required.

Missed dose-
1. If you are using this medicine regularly and you miss a dose, use it as soonas possible.
2. Then use the remaining dose fotbthat day at regularly spaced intervals.
3. Do not double doses.

VASSOPRESSORS USED IN SHOCK-  include-

Inotropic effects -
Isoproternol, Dobutamine, Dopamine, Ephinephrine,

Mixed  effects-
Norephinephrine, Ephedrine, Mephentermine

Pressors effects-
Metaraminol
Methoxamine
Phenylephrine

Pharmacology:
A potent sympathomimetic amine that increase both systolic and diasystolic blood pressure, primarily by vasoconstriction

Pharmacokinetics:
The pressor effect begins 1 to 2 minutes after IV infusion. The effect lasts for about 20 minutes to 1 hour.

 

Pregnancy:
Give to a pregnant woman only if needed.

Lactation:
Drug is secreted in breast milk. Administer with caution

Children-
Safety and effectiveness in children have not been established.