*5.4.1* Α*-1 adrenergic receptor blockers*

The role of α-1 adrenergic receptor blockers in the treatment of children with DV is controversial, as the mechanism of action at the level of the external urethral sphincter is still insufficiently known [61]. The possible mechanism of action is traditionally assumed to be relaxation of the periurethral, prostatic and bladder neck smooth muscles. In the study of Yucel et al., it has been shown that the effects of α-1 adrenergic blockers in reducing post-void residual urine can be compared with the effect of biofeedback [62].

### *5.4.2 Muscle relaxants*

As DV is characterized by the inability of relaxation of the external urinary sphincter during urination, it was considered that muscle relaxant could be used in treatment.

Baclofen has been shown to be effective in reducing skeletal muscle spasticity, as well as in patients with striated sphincter dyssynergia [63]. However, the therapeutic effect is achieved only after the application of high doses. Serious adverse effects, especially after abrupt withdrawal, reduce its efficacy and safety in children with DV [64]. Therefore, tizanidine, a muscle relaxant used in many studies as a short-acting muscle relaxant due to spasmolytic action, was used. In a prospective, randomized study, 40 children with DV were divided into two groups [65]. The first group was treated with tizanidine (an imidazole derivative), while the

second group of children was treated with α-blocker (doxazosin). After 6 months of follow-up, both groups had similar improvement in symptoms and uroflowmetry parameters. In the doxazosin-treated group, urgency was the only symptom that showed a significant reduction after therapy. However, nocturnal enuresis, urgency, and daytime incontinence were significantly reduced in the tizanidine-treated group. Side effects were reported in 6 patients (15%). Epigastric pain was reported in two children (10%) receiving doxazosin. In the tizanidin group, loss of appetite was noted in two children (10%), epigastric pain in one (5%) and headache in one child (5%).
