What are the general causes of rhinitis and rhinorrhoea?

There are various causes of these conditions, including:

1. Allergens (allergic rhinitis)
2. The environment (non-allergic rhinitis in reaction to cold air)
3. Chemicals
4. Physical damage

• Which drug groups can be used for the treatment of rhinorrhoea? Name examples from each group.

1. Alpha1-agonists eg: oxymethazoline
2. Antihistamines eg: rupatadine
3. Corticosteroids eg: betamethasone
4. Mast cell stabilisers eg: ketotifen
5. Mucolytics eg: mesna
6. Antibiotics eg: neomycin
7. Diverse drugs eg: normal saline solutions

• How do the decongestants differ with respect to the mechanism of action and duration of action?  How are they administered typically?

Decongestants can be administered vie IV, orally or topically. The various administration forms  have different duration of actions. Their mechanism of actions also differ for example topical administrations have less side effects than those administered systemically. this is also the reason decongestants are applied topically in rhinitis  and rhinnorrheoa. 

• What is rhinitis medicamentosa?  How is it treated?

This is the severe drying of the nasal mucosa and is often caused by the prolonged us (more than 7days) of a topical decongestant. it is treated by cessation of the decongestant and rehydrating the patient.

• How does the first and second generations of antihistamines differ with respect to the mechanisms according to which rhinitis and rhinorrhoea are relieved?  What are the advantages of the second generation of antihistamines?  Why should they not be used to relieve cold rhinitis?

They 1st generation causes severe sedation as  well as antimuscarinic effects, which isn't seen nearly as prominantly in the 2nd generation antihistamines. the second generation antihistamines are used more often in allergic rhinitis for these drugs has the ability to prevent the release of histamine from mast cells, something that 1st generation drugs can not do.

• When are corticosteroids, anti-allergic drugs, mesna and normal salt solution valid and how are they administered? 

corticosteroids are used prophylactically and chronically (topically).

Anti-allergic drugs are used in allergic rhinitis where they prevent the release of inflammation mediators (topically)

Mesna is a mucolytic used when thick and tough mucus needs to be eliminated from the nasal cavity.

Normal saline solutions are ideal for they have no adverse effects. It should be used  to rinse the nasal cavity (topically.) it is ideal in children and geriatric patients seeing that they are more susceptible  to systemic decongestant's side effects.