## 1 Introduction  
The intranasal (IN) administration of drugs often appears as a valid alternative to oral route, that can experience limitations such as poor absorption in the gastrointestinal tract and hepatic first-pass effect, or the impossibility to administer the drug to unconscious patients, like in many emergency situations [1]. Due to the relatively large surface of nasal mucosa and the high level of vascularization, a drug administered intranasally can be quickly absorbed and distributed in the systemic circulation, thus offering a valid tool for the therapy of keen conditions, such as seizure or acute pain [2]. Furthermore, IN is a non-invasive way of administration, therefore encountering the favorable compliance of children and elderly patients. IN administration is currently proposed for a topical effect on the nasal mucosa (e.g., therapy of inflammation, allergies or nasal congestion) but also to exert a systemic effect, such as with hormones, analgesic and anti-inflammatory drugs, cardiovascular and antiviral agents [3]. More recently, the 'nose-to-brain' (N2B) route is under intense investigation as a strategy to overcome the blood-brain barrier and convey drugs directly in some brain districts [4; 5]. IN administration has been associated in the very last years with innovative drug delivery technologies. Micro- and nanosized drug delivery systems (DDS) can in fact modulate the rate or time of drug release in the nasal mucosa, thus definitely controlling drug local effect or its levels in the systemic circulation [6]. Among the clinical conditions in which a IN administration could support the therapy are inflammatory states, often associated with pain. Non-steroidal anti-inflammatory drug (NSAIDs) are undoubtedly the pharmacological class of drugs more used, especially in self-therapy. Most of these drugs are however also associated to gastrolesivity after oral administration, thus requiring technological approaches to modulate the time and site of release in the gastro-intestinal tract. Therefore, IN route could be an interesting alternative for this drug class, to reach both goals of a quick adsorption and a reduced irritant effect on the stomach mucosa [7]. A nasal spray based on ketorolac tromethamine even reached the market [8]. Diclofenac (2-[2-(2,6-dichloroanilineo)phenyl]acetic acid; DIC) is a phenylacetic derivative of propionic acid. It is a non-steroidal anti-inflammatory drug (NSAID), largely used, in different dosage forms, with the aim to reduce joint inflammations and pain [9]. It is characterized by a low water solubility, and it is thus often applied as a soluble sodium of potassium salt [10; 11]. Diclofenac epolamine (DIEP) (diclofenac N-(2-hydroxyethyl)-pirrolidine), is a salt form very soluble in water and polar solvents. High concentrations of DIEP aqueous solutions show a tenstole-like behavior [12]. Solubility and surfactant properties of DIEP enhance its permeability through the biological membranes [13]. The relatively high gastro-intestinal toxicity tolerability of DIC, in comparison with most other NSAIDs [14], makes it a valid pharmacological tool. Unfortunately, it shows an unpleasant pharmacokinetic profile, including a short plasma lifespan (1.1 h), that limits the clinical use [10; 15]. Encapsulation of DIC and its salts in nano- and microparticle systems that allow a prolonged release could therefore be a valid strategic approach to improve their efficacy [16; 17; 18; 19; 20; 21]. In this study we evaluated new colloidal systems for the IN delivery of DIC and DIEP. Eudragit(r) RS100 (RS) and RL100 (RL) are copolymers of poly(ethylacrylate, methyl-methacrylate and chlorotrimethyl-ammonioethyl methacrylate), containing an amount of quaternary ammonium groups between 4.5 and 6.8% and 8.8 and 12% for RS and RL, respectively. Both are insoluble at physiological pH values and capable of swelling [22], thus representing good materials for the dispersions of drugs [23; 24].