It may occur as a result of colds, flu, sinusitis, rhinitis, hay fever, allergies, laryngopharyngeal acid reflux or throat disorders. Certain factors such as inhaling irritants (smog, perfume, dust or smoke), living in a dry environment, dairy products, coffee, alcohol and excessive use of nasal sprays may also contribute to post nasal drip. Also, post nasal drip has been known to be worse upon waking in the morning as gravity causes the mucous to drain down into the throat and lower respiratory passages whilst you are lying asleep.
In a pharmacokinetic study comparing flunisolide nasal solution (flunisolide nasal spray .025%) (29 mcg per spray) with flunisolide nasal solution (flunisolide nasal spray .025%) (25 mcg per spray), the original formulation, the two formulations were not bioequivalent. The total absorption of flunisolide nasal solution (29 mcg per spray) was 25% less than that of flunisolide nasal solution (25 mcg per spray), and the peak plasma concentration was 30% lower. The clinical significance of these differences is likely to be small, particularly since clinical efficacy is attributable to a local effect on nasal mucosa (see Pharmacodynamics ).
In animal studies corticosteroids have been shown to be teratogenic. There are no adequate studies in pregnant women. AU TGA pregnancy category B3: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans. US FDA pregnancy category C: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.