// Material Select Initialization
$(document).ready(function() {
$('.mdb-select').materialSelect();
});

input[type="text"]:not(.browser-default){
  text-align: right;
  margin-right: 10px;
}

.caret {
  margin-left: 10px;
}

.select-wrapper input.select-dropdown {
 padding-right: 15px!important;
}

.input-group-tex {
  z-index: -1;
  position: absolute;
  top: 50%;
  left: 15px;
  transform: translateY(-50%);
}

.prov {
  position: relative;
}

<!-- Font Awesome -->
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.11.2/css/all.css">
<!-- Bootstrap core CSS -->
<link rel="stylesheet" href="https://motustrength.it/MDB4.19.1-PRO/css/bootstrap.min.css">
<!-- Material Design Bootstrap -->
<link rel="stylesheet" href="https://motustrength.it/MDB4.19.1-PRO/css/mdb.min.css">

  <!-- Start your project here-->  
<div class="prov">
  <span class="input-group-tex">Sesso</span>
  <select class="mdb-select" id="inputGroupSelect03" > 
    <option class="seleziona" selected value="0">Seleziona</option>
    <option id="sexuomo" name="radios" value="Male"  required class="sexbtn">Uomo</option>
    <option id="sexdonna" name="radios" value="Female" form="bmrcalc" required class="sexbtn">Donna</option>
  </select>
</div>  
  <!-- End your project here-->

  <!-- jQuery -->
  <script type="text/javascript" src="https://motustrength.it/MDB4.19.1-PRO/js/jquery.min.js"></script>
  <!-- Bootstrap tooltips -->
  <script type="text/javascript" src="https://motustrength.it/MDB4.19.1-PRO/js/popper.min.js"></script>
  <!-- Bootstrap core JavaScript -->
  <script type="text/javascript" src="https://motustrength.it/MDB4.19.1-PRO/js/bootstrap.min.js"></script>
  <!-- MDB core JavaScript -->
  <script type="text/javascript" src="https://motustrength.it/MDB4.19.1-PRO/js/mdb.min.js"></script>