Introduction
Dexmedetomidine hydrochloride is a white or almost white powder that is freely soluble in water and has a pKa of 7.1. Dexmedetomidine hydrochloride is a potent α2-adrenoceptor agonist, which produces and analgesia, about 8 times higher selective affinity for the α2/α1-adrenoceptor than clonidine. Its structure is showed below:
Fig. 1 Structure of dexmedetomidine hydrochloride
Used as sedative
- Application
Since the first approval was acquired in the US in 1999, dexmedetomidine hydrochloride has been widely used in sedation. Dexmedetomidine hydrochloride is notable for its ability to provide sedation without risk of respiratory depression (unlike other commonly used drugs such as propofol and fentanyl) and can provide cooperative or semi-rousable sedation.
- Intensive Care Sedation
Dexmedetomidine hydrochloride can be used as a sedative (calming agent) if adults need to be calm or sleepy in the Intensive Care Unit whilst they are being ventilated (on a breathing machine). It may be given as an infusion up to 24 hours.
- Procedural Sedation
Dexmedetomidine hydrochloride can be given to adults prior to an operation if they are not on a ventilator (breathing machine) if it is required for the procedure or surgery that they be sleepy and calm.
Fig. 2 Used in sedative injection
- Mechanism of action
Dexmedetomidine hydrochloride selectively binds to and activates presynaptic alpha-2 adrenoceptors located in the brain, thereby inhibiting the release of norepinephrine from synaptic vesicles. This leads to an inhibition of postsynaptic activation of adrenoceptors, which inhibits sympathetic activity, thereby leading to analgesia, sedation and anxiolysis. Physiology of the α 2-adrenoceptor agonists receptor is showed in figure 3 [1].
Fig. 3 Physiology of the α 2-adrenoceptor agonists receptor
- Applied Case
One hundred and two pregnant women who underwent cesarean section were selected from August 2016 to July 2017 in People's Hospital of Zhangqiu District and randomly divided into control group and observation group. Control group was anesthetized with bupivacaine hydrochloride, and morphine + ropivacaine hydrochloride were given postoperatively. Observation group received intraoperative anesthesia with bupivacaine hydrochloride and Dex, and Dex + ropivacaine hydrochloride were given for postoperative analgesia. Hemodynamic factors were compared between the two groups. Postoperative Ramsay sedation score, the incidence of adverse reactions and the incidence of transient neurological syndrome (TNS) were compared between the two groups. Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) scoring were performed to evaluate the cognitive function of the two groups. The use of Dex anesthesia in cesarean section can achieve more stable hemodynamic conditions during perioperative period and more obvious analgesic effect after operation. It also reduced the incidence of postoperative TNS and cognitive dysfunction and had important clinical significance [2].
- Side effects
Treatment-emergent adverse reactions occurring at an incidence of >2% are provided in Table 1[3]. The most frequent adverse reactions were hypotension, bradycardia and dry mouth.
| Adverse Event | All Dexmedetomidine Injection (N = 1007) (%) | Randomized Dexmedetomidine Injection (N = 798) (%) | Placebo (N = 400) (%) | Propofol (N = 188) (%) |
| Hypotension | 25% | 24% | 12% | 13% |
| Hypertension | 12% | 13% | 19% | 4% |
| Nausea | 9% | 9% | 9% | 11% |
| Bradycardia | 5% | 5% | 3% | 0 |
| Atrial Fibrillation | 4% | 5% | 3% | 7% |
| Pyrexia | 4% | 4% | 4% | 4% |
| Dry Mouth | 4% | 3% | 1% | 1% |
| Vomiting | 3% | 3% | 5% | 3% |
| Hypovolemia | 3% | 3% | 2% | 5% |
| Atelectasis | 3% | 3% | 3% | 6% |
| Pleural Effusion | 2% | 2% | 1% | 6% |
| Agitation | 2% | 2% | 3% | 1% |
| Tachycardia | 2% | 2% | 4% | 1% |
| Anemia | 2% | 2% | 2% | 2% |
| Hyperthermia | 2% | 2% | 3% | 0 |
| Chills | 2% | 2% | 3% | 2% |
| Hyperglycemia | 2% | 2% | 2% | 3% |
| Hypoxia | 2% | 2% | 2% | 3% |
| Post-procedural Hemorrhage | 2% | 2% | 3% | 4% |
Table 1: Adverse Reactions with an Incidence >2%-Adult Intensive Care Unit Sedation Population<24 hours
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References
- Ralph Gertler. Dexmedetomidine: A Novel Sedative-Analgesic Agent. Proceedings (Baylor University. Medical Center) 14(1):13-21.
- Dehua Kong, Jianhua Bai, Suqiao Ma, et al. Effects of dexmedetomidine hydrochloride on hemodynamics, postoperative analgesia and cognition in cesarean section. Experimental and Therapeutic Medicine, June 27, 2018: 1778-1783.
- Dexmedetomidine Hydrochloride Injection. Medically reviewed by Drugs.com. Jan 1, 2021.
