HISTAMINE SENSITIVITY IN THE NASAL-MUCOSA DURING LONG-TERM USE OF XYLOMETAZOLINE IN THE DOUBLED RECOMMENDED DOSE

It has been suggested that the severity of rhinitis medicamentosa is d ependent on the length of time the drug has been used, on how frequent ly it is used, and on the amount administered. It has been reported th at a 4-week use of oxymetazoline in the recommended dose induced a reb ound swelling and an increased histamine sensitivity as a sign of rhin itis medicamentosa and nasal hyperractivity. In order to study the imp act of an increased amount of vasoconstrictor on the histamine sensiti vity, nine healthy subjects had xylometazoline nasal spray in the doub led recommended dose (1.0 mg/mL; 0.28 mL in each nostril three times d aily) for 30 days. After 10 days on the drug the histamine sensitivity was slightly increased, and after another 20 days the sensitivity was significantly increased compared to that before the start of the medi cation (P<0.01). When comparing the results from this study with the c orresponding ones from the oxymetazoline study, no difference in the h istamine sensitivity was seen. One month after the medication was fini shed three subjects still had an increased sensitivity to histamine. I t was concluded that the doubled recommended dose of xylometazoline di d not further increase the elevated histamine sensitivity seen followi ng vasoconstrictor used in recommended dose. The results also indicate that the increased histamine sensitivity was not caused by the preser vatives. Finally, the subjects achieved a drug-induced non allergic na sal hyperreactivity (NANH) that in some subjects persisted for a long time.