Acepromazine or Dexmedetomidine?

9 de September de 20249 de September de 2024 Adriano Carregaro

It seems like everything nowadays leads to conflict and polarization, doesn't it? We've seen a debate about using acepromazine or dexmedetomidine in pre-anesthetic medication for dogs and cats. Well, this debate is somewhat baseless because these drugs aren't really "comparable." What we aim to achieve with one is not always what we aim to achieve with the other.

As we discussed in the video lesson on phenothiazines, from the "Anesthesia is Basic" playlist, acepromazine was one of the most commonly used drugs for pre-anesthetic medication, especially in dogs. For cats, we mentioned that its effect is not very interesting... (click here to find out more, ok ?). However, recently dexmedetomidine has been prioritized in premedication for both dogs and cats. It’s true that it is somewhat better than xylazine, as we discussed in the video lesson on alpha-2 adrenergic agonists, but is it really better than acepromazine? Let’s “try to compare these two drugs” to see if this discussion makes sense or not…

Tranquilization vs Sedation

The first point we need to understand is that acepromazine is a tranquilizer. Therefore, in appropriate doses, it promotes tranquilization. Even if high doses are administered, acepromazine will not induce sedation. So, if we are looking for sedation, acepromazine is not the best option.

Dexmedetomidine, on the other hand, is a sedative. So, in appropriate doses, it promotes sedation. However, in lower doses, it can promote only tranquilization. This way, we can "adjust" the impact of dexmedetomidine on depression according to the dose. This is undoubtedly an advantage!

Analgesia

Here, there’s not much room for debate... acepromazine does not cause analgesia, unlike dexmedetomidine, which is considered a good analgesic. However, when we use acepromazine in pre-anesthetic medication, we typically combine it with an opioid, promoting neuroleptoanalgesia. This changes everything! In this case, we will have sedation and analgesia; this is because the combination of acepromazine with an opioid leads to greater central nervous system depression, causing sedation, while the analgesia will come from the opioid. Depending on the combination, we might achieve sedation as intense or more intense than dexmedetomidine, and the same goes for analgesia. Think about that!

Cardiovascular Impact

This point might be the most important in this "comparison." As we have seen in the videos about pre-anesthetic medication, both acepromazine and dexmedetomidine cause cardiovascular changes. However, the effects of dexmedetomidine are certainly much more intense.

Acepromazine causes a decrease in blood pressure due to its effect on alpha-1 receptors and a reduction in myocardial contractility. This can lead to a compensatory effect of increased heart rate, at least in dogs. However, this effect might be subtle when using clinical doses, between 0.02 and 0.03 mg/kg.

Dexmedetomidine, on the other hand, causes more intense changes in cardiovascular parameters. The main effect is hypertension, resulting from the activation of alpha-2 arterial receptors. This leads to an increase in peripheral vascular resistance and, due to vagal stimulation, will result in reflex bradycardia.

Therefore, both of these medications cause considerable changes, although dexmedetomidine’s effects are more intense. Ideally, we should avoid both drugs in patients with heart conditions, especially when these animals show clinical symptoms.

Other effects

Other important effects to consider are that acepromazine can cause temporary splenomegaly due to sequestration of red blood cells, block the thermoregulatory center, and has no antagonist; that is, we need to wait for its effects to wear off, which can last up to 6 hours. On the other hand, dexmedetomidine reduces antidiuretic hormone levels, leading to increased urination in the animal, and raises blood glucose levels, which should be considered in diabetic patients, for example.

Another important point is the cost of dexmedetomidine, which can be between 10 and 20 times more expensive than acepromazine. Since we can use both medications, this factor should also be considered.

Given all this, we see that each medication has its advantages and disadvantages. What we need to understand is what we want from the medication, what benefits it can offer us, and also the undesirable effects, especially with the aim of providing the best care for our patient.

So, can you choose now?

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Find out more:
– Carregaro AB. Medicação pré-anestésica. In: Massone F. Anestesiologia Veterinária – Farmacologia e Técnicas. Ed Guanabara Koogan. 7a ed. 2019, 15-20.
– Cortopassi SRG, Fantoni DT. Medicação pré-anestésica. In: Fantoni DT, Cortopassi SRG. Anestesia em Cães e Gatos. 2a ed. Editora Rocca, 2010. 217-227.
– Monteiro ER, Campagnol D, Parrilha LR, Furlan LZ. Evaluation of cardiorespiratory effects of combinations of dexmedetomidine and atropine in cats. J Fel Med Surg, 11: 783-792, 2009.

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