Noradrenaline: What is it? Formula, Presentation, Indications, Dosage, Side Effects, Warnings and Interactions

Also known as norepinephrine, it is one of the main neurotransmitters in the sympathetic nervous system.

It increases the heart rate, increases blood pressure, dilates the bronchi, dilates the pupils, increases the contractility of the heart muscle, inhibits salivation and urination, and decreases blood flow to the digestive system.

It also increases blood flow to skeletal muscles, promotes glycogenolysis, gluconeogenesis, and lipolysis, increases mental alertness, and many other effects.

Chemical formula of norepinephrine

  • C8H11NO3.

Presentation

Concentrate for solution for infusion of Noradrenaline or Norepinephrine in a 1 mg / ml.

Indications of norepinephrine

Norepinephrine is used to treat sudden, life-threatening low blood pressure , that is, in the case of acute hypotension.

Mechanism of action

Norepinephrine normally produces effects such as increased heart rate, increased blood pressure, widening of the pupils, widening of the airways in the lungs, and narrowing of the blood vessels in non-essential organs.

This allows the body to function well in stressful situations.

Norepinephrine works by stimulating receptors called adrenoceptors, which are found throughout the body.

When injected into a vein, norepinephrine primarily acts on a type of adrenoceptor known as an alpha receptor. These are found in the muscle within the walls of the peripheral blood vessels.

Stimulating these alpha receptors causes the muscle to contract, which causes the blood vessels to narrow and constrict.

By narrowing the blood vessels in the extremities, norepinephrine redirects blood to essential organs such as the heart and brain .

It also produces a greater resistance for the heart to beat, and this increases blood pressure.

Dose

The concentration of the prepared infusion is 40 mg / liter of norepinephrine base (80 mg / liter of norepinephrine tartrate), the initial infusion rate, with a body weight of 70 kg, should be between 10 ml / hour and 20 ml / hour (0.16 to 0.33 ml / min).

Some clinicians usually start with a lower initial infusion rate of 5 ml / hour (0.08 ml / min), equivalent to 0.2 mg / hour of norepinephrine base or 0.4 mg / hour of norepinephrine tartrate.

Norepinephrine side effects

Some of the side effects that occur and are known to be associated with norepinephrine are:

  • General malaise and vomiting.
  • Lack of appetite.
  • Decreased supply of oxygen around the body (hypoxia), particularly in the tissues of the extremities (peripheral ischemia).
  • Palpitations and irregular heartbeats or cardiac arrhythmias.
  • Slower or faster heart rate (bradycardia or tachycardia).
  • High blood pressure (hypertension).
  • Short of breath.
  • Headache.
  • Difficulty to sleep.
  • Anxiety.
  • Tremors
  • Confusion.
  • Soft spot.
  • Difficulty urinating.
  • Elevated pressure in the eyeball ( angle-closure glaucoma ).

Warnings and Contraindications

This medicine should not be administered if the patient is allergic to any of its ingredients.

Elderly patients are found to be especially sensitive to the effects of norepinephrine.

Special caution should be exercised in patients with thrombosis in the artery supplying blood to the heart (coronary) and in the artery supplying blood to the intestines (mesenteric).

Also in one of the blood vessels in the extremities (peripheral vascular) because norepinephrine can increase ischemia and extend the area of ​​the infarction.

Similar caution should be exercised in patients with hypotension after myocardial infarction .

In patients with variant angina pectoris, not caused by exertion (Prinzmetal’s angina) and in patients with diabetes, hypertension or an overactive thyroid gland (hyperthyroidism).

Those with low levels of oxygen in the tissues ( hypoxia ), with an abnormally high amount of carbon dioxide in the blood ( hypercapnia ).

Norepinephrine can reduce the blood supply to the placenta. It should only be used during pregnancy in an emergency, where the expected benefit to the mother outweighs any possible risk to the developing baby.

There is not enough information available about the safety of this medicine for the baby during breastfeeding.

However, it is not well absorbed from the intestine so norepinephrine is unlikely to pass into breast milk and affect the nursing infant.

High intravenous doses of the drug can reduce or decrease milk production. However, you should consult your doctor or stop breastfeeding.

Norepinephrine interactions

There may be an increased risk of high blood pressure or effects on heart rhythm if this medicine is used concomitantly in people taking any of the following medicines:

  • Beta blockers like propranolol.
  • General anesthetics.
  • Linezolid.
  • Antidepressants such as phenelzine.
  • Rasagiline or selegiline for parkinson’s disease.
  • Tricyclic antidepressants such as amitriptyline.