NASYA

KARMUKATHA

The respiratory tract, which includes the

nasal mucosa hypopharynx large airways & small airways

provides a relatively large mucosal surface area of approx. 100 m (in normal adult) for drug absorption

Cross-sectional view

Pathways for nasal absorption

Nasal site of drug spray & absorption

CROSS-SECTIONAL VIEW

a – nasal vestibule d – middle turbinate

b – palate e – superior turbinate (olfactory mucosa)

c – inferior turbinate f – nasopharynx

Site of drug

spray &

absorption

Pathways for nasal

absorption Absorption through the olfactory neurons

- transneuronal absorption. Olfactory epithelium is

considered as a portal for substances to enter CNS

Absorption into the cerebrospinal fluid

Absorption through the supporting cells & the

surrounding capillary bed

- venous drainage

Transneuronal absorption

Olfactory nerve – 1st cranial sensory nerve

Venous drainage

•Nasal secretion of adult : 5.5-6.5

•Infants and children: 5-6.7

•It becomes alkaline in conditions such as acute rhinitis, acute sinusitis.

•Lysozyme in the nasal secretion helps as antibacterial and its activity is diminished in alkaline pH

Nasal pH

Factors

affecting

drug

absorption

Drug concentration

Vehicle of drug delivery

Mucosal contact time

pH of the absorption site

Size of the drug molecule

Relative lipid solubility

Degree of drug’s ionization

Physiological effects

- Drug metabolism in the respiratory tract &

reduction of systemic effect

- Mucociliary transport causing

increased or decreased drug residence

time

- Protein binding

Physiological effects....

- Local or systemic effects of propellants,

preservatives, or carriers

- Local toxic effects of the drug

Eg., edema, cell injury, or altered tissue

defenses

1. Effect of particle size

2. Effect of molecular size

3. Effect of solution pH

5. Effect of drug concentration

4. Effect of drug lipophilicity

1.Effect of particle size (aerodynamic size distribution)

- Access to distal airways is a function of particle size

- Large particles (> 7 microns) will be lost in the

gastrointestinal tract

- Intermediate particles (3 to 7 microns) reach the

actual site of action

- Small particles (< 3 microns) will be lost in exhaled

breathe

2. Effect of molecular size

- A good systemic bioavailability can be achieved for

molecules with a molecular weight of up to 1000

Daltons when no absorption enhancer is used

- Higher the molecular size, lower the nasal absorption

2. Effect of molecular size.....

Absorption enhancers: Polyacrylic acid

Sodium Glycocholate

Sodium Deoxycholate

Polysorbate 80 etc.

- With the assistance of absorption enhancer, a good

bioavailability can be extended to a molecular

weight of at least 6000 Daltons

3. Effect of solution pH

- Nasal absorption is pH dependent

- Absorption is lower as the pH increases beyond

the dissociation constant

- Absorption is higher at a pH lower than the

dissociation constant (pKa) of the molecule

4. Effect of drug

lipophilicity- Polar (water soluble) drugs tend to remain on the

tissues of the upper airway

- Lipid soluble drugs are absorbed more rapidly

than water soluble drugs

- Non-polar (lipid soluble) drugs are more likely to

reach distal airways

5. Effect of drug

concentration

- The absorption follows first-order kinetics

- Absorption depends on the initial concentration of

the drug

Nasya dravya karmukata

Nasya dravya karmukata

Substances which produces smell uaually have certain characterstics.

1.Volatile

2.they are atleast slightly water soluble

3.they are usually highly lipid soluble. The cilia of olfactory cellls and the portions of the body of the

olfactory cells relatively contains large quantities of lipoid materials.

A substance which is lipid soluble can cause marked stimulation of an olfactory cell.

The substance which is given through the nostrils can irritate the mucosa of the nose and drains the accumulated phlegm through the nostrils.(in teekshna nasya)