Naphazoline applications

Vasoconstriction. Local application of a-sympathomimetics can be employed in infiltration anesthesia (p. 204) or for nasal decongestion (naphazoline, tetra-hydrozoline, xylometazoline pp. 90, 324). Systemically administered epinephrine is important in the treatment of anaphylactic shock for combating hypotension. 

Vasoconstriction induced by an a-sympathomimetic is followed by a phase of enhanced blood flow (reactive hyperemia, A). This reaction can be observed after the application of a-sympa-thomimetics (naphazoline, tetrahydro-zoline, xylometazoline) to the nasal mucosa. Initially, vasoconstriction reduces mucosal blood flow and, hence, capillary pressure. Fluid exuded into the interstitial space is drained through the veins, thus shrinking the nasal mucosa. 

Figure 4 presents an example of rapid pKa measurement using a pressure-assisted system in combination with a photodiode array (PDA) detector. The migration time of DMSO (EOF marker) was measured at 220 nm, whereas the migration time of the analyte, naphazoline, was measured at 270 nm. The CE run time as well as data analysis time was drastically reduced. Consequently, this system allows the analysis of more than 96 compounds in one day. The limitation of this method is the application to drugs without UV chromophore at more than 250 nm. In some cases, it was effective to remove DMSO by evaporation under vacuum followed by the addition of methanol or acetonitrile as a neutral marker. 

Compounds like naphazoline and xylometazoline are relatively selective agonists, which on topical application produce local vasoconstriction. They are used as nasal decongestants and have longer duration of action. Prolonged use can produce atrophic rhinitis and anosmia. 

Disposition in the Body. Systemic absorption has been reported following topical application of solutions of naphazoline. It is not used systemically but is readily absorbed from the gastrointestinal tract. 

The synthetic adrenergic agonists—phenylephrine, naphazoline, oxymetazoline, and tetrahydrozoline—are available as ocular decongestants (Table 13-2). After topical application to the eye, constriction of conjimcti-val blood vessels occurs at drug concentration levels that generally do not cause pupillary dilation. These agents provide only palliative therapy, because they have no effect on the conjimctival response to antigen. 

A 71-year-old Japanese man, who was using an over-the-counter formulation, Makiron, for minor wounds, developed an itchy rash with seropapules and erosions on his right leg at the site of application (5). Makiron contains 0.1% cinchocaine hydrochloride and chlorphe-namine maleate as well as naphazoline hydrochloride and benzethonium chloride. On patch testing, he was positive to both chlorphenamine and cinchocaine. 

A selective CZE microassay was developed for the determination of dexa-methasone phosphate and its major metabolite, dexamethasone, in tears (325). An internal standard, indoprofen, was used for quantitation. The limits of detection and quantification were 0.5 and 2.0 pg/mL, respectively. The quantitative method was essential for the in-vivo determination of the dexamethasone concentration-time profiles in tears after the application of the anti-inflammatory drug. Two examples of rapid and simple drug analysis in pharmaceutical formulations using capillary electrophoresis can be found in the methods described for the separation of naphazoline, dexamethasone, and benzalkonium in nose drops (326). 

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