4 doctors agreed: Maybe not allergic: It's not unusual for pain medications such as morphine, demerol, or Dilaudid to be associated with some itching. They all can cause histamine release. This doesn't necessarily mean you are allergic to them. True allergy produces severe symptoms such as hives and trouble breathing. Sometimes Benadryl can help with itching. Or you can ask your doctor to try a different pain medication.
What is the most important electrolyte for the maintenance of osmotic pressure and volume in the extracellular fluid compartment? The most abundant positive ion or cation in the extracellular fluid  is sodium (Na+). Chloride (Cl-) is the most abundant negative ion  or anion.
1 Extracellular fluid is found in the following compartments: plasma, interstitial fluid, and trancellular fluid.  The cytosol is a complex mixture of substances including proteins, ions, and organelles dissolved in water.