ACLS and Vasopressin

ACLS and Vasopressin

Vasopressin is a primary drug used in the pulseless arrest algorithm. In high concentrations, it raises blood pressure by inducing moderate vasoconstriction, and it has been shown to be more effective than epinephrine in asystolic cardiac arrest (Wenzel V, Krismer AC, Arntz HR, Sitter H, Stadlbauer KH, Lindner KH (January 2004). “A comparison of vasopressin and epinephrine for out-of-hospital cardiopulmonary resuscitation”. N. Engl. J. Med. 350 (2): 105–13. doi:10.1056/NEJMoa025431. PMID 14711909.)

One major indication for vasopressin over epinephrine is its lower risk for adverse side effects when compared with epinephrine. With epinephrine, some studies have shown a risk of increased myocardial oxygen consumption and post arrest arrhythmias because of an increase in heart rate and contractility (beta 1 effects). Vasopressin also is thought to cause cerebral vessel dilation and theoretically increase cerebral perfusion.

Trivia: Another name for vasopressin is antidiuretic hormone (ADH).


Vasopressin may be given IV/IO or by endotracheal tube.


40 units of vasopressin IV/IO push may be given to replace the first or second dose of epinephrine, and at this time, there is insufficient evidence for recommendation of a specific dose per the endotracheal tube.
In the ACLS pulseless arrest algorithm, vasopressin may replace the first or second dose of epinephrine.

Return to main ACLS Pharmacology page.


  1. Pradeep Pathak says

    Hi Jeff,
    I like the contents on this website very much. I would like to ask is that 1st dose of Amiodarone is given after the 3rd shock, so the 2nd dose is given after the 4th shock or 5th shock?

    I mean to say that the Algorithm is 1st shock- 2nd shock – Epinephrine-3rd shock – Amiodarone- 4th shock-Amiodarone or after 4th shock it is Epinephrine and Amiodarone after 5th shock.


    • says

      The second dose of amiodarone can be given after the fourth or fifth shock. It is really up to the discretion of the provider whether they give the amiodarone after the fourth or fifth shock.

      Kind regards,

  2. MACKY says

    Vasopressin can replace the first or second dose of epinephrine. My question is why are we giving it in the initial phase of resuscitation only( First or Second dose of epinephrine)? Why can’t we give it in replacement of subsequent doses of epinephrine?

    • says

      The half-life of epinephrine is 2 minutes. This is why you give the medication every 3-5 minutes.
      It is the same with vasopressin. The half-life of vasopressin is 20 minutes. This is why it can be given only one time during a code as a replacement for the first or 2nd dose of epinephrine.
      Kind regards,

  3. Michael says

    Why is the 1st epinephrine given after the 2nd shock? If circumstances are right, say in a hospital or in the middle of transport, and an IV is already in place, why not give the epinephrine after the 1st shock?

    • says

      The algorithm is designed to start at the very beginning with no IV access and no drugs available. It is given after the 2nd shock of the algorithm so as to emphasize the CPR and shocks which are the only interventions that have been shown to improve survival to hospital discharge. This algorithm is not all inclusive and can be “tweaked” if the situation allows. The algorithm itself is generic and does not take into consideration many of the variables that can exist in a real code setting.
      AHA states that health care providers can tailor the sequence of events to the situation at hand. Very often, I have seen epinephrine given very early in a code when extra hands were available and an IV was already in place. If you only have two people available, the pushing of medications will not be of primary importance and will not take place before the 2nd shock because the two people will be performing other more critical interventions.

      Kind regards,

    • Louis says

      Epinephrine is also naturally released by the body during defibrillation and so is not always necessary until after the second shock. My personal choice is vasopressin over epinephrine anyway as some studies have shown it to cause less side effects and theoretically iincreass cerebral perfusion .

  4. Elizabeth Novotny says

    In the pre-course assessment for the AHA on-line it asks the question…in pulseless vtach a patient has received one dose of epinephrine and two shocks, the next medication to expect should be amiodarone. I do not understand why vasopressin is not the correct medication . Could you explain this to me? I cannot thank you enough for this course, and your help! It has been wonderful!
    Thank you and God bless,

    • says

      Epinephrine is given after the second shock. Any subsequent doses of epinephrine are given every 3 to 5 minutes. Epinephrine is basically on it’s own timetable after the initial dose.
      The first dose of Amiodarone is always given after the third shock. Any subsequent dose of amiodarone is given after the first dose has had adequate time to circulate. This usually occurs any time after the fourth shock, but always during CPR.

      Kind regards,

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