Otic drug delivery

What is otic drug delivery?

Drug delivery to the ear canal

Why may drugs need to be delivered to the ear?

Treatment of infections, pain or inflammation

What are most otic drugs comprised of?

Aqueous - purified water - or oily - mineral oils solutions 

What formulations are mostly associated with removing earwax?

Lipophilic formulations 

What normally affects vehicle choice in otic drug delivery?

Drug solubility in aqueous/lipophilic media

Why is glycerol used in otic drugs delivery?

Hygroscopic nature helps to reduce inflammation and remove exudate from inflamed tissues

Why do otic preparations need preservatives?

Usually multi-dose preparations so need preservatives 

What preservatives are used in otic drug delivery?

Similar to nasal/ocular - chlorobutanol 0.5% w/w, various parabens 0.2% w/w, benzalkonium chloride 0.002-0.02% w/v, thimerosal 0.002-0.005% w/v

When are the preservatives benzalkonium chloride and thimerosal used in otic drug delivery?

In combined otic preparations

When are preservatives not often required in otic drug delivery?

When formulation has a low water content 

How can viscosity be modified in otic drug delivery for aqueous systems?

Hydrophilic polymers added

When are viscosity modifiers not necessary for otic drug delivery?

When the systems already cause an increase in viscosity e.g., using glycerol increases vehicles viscosity

Why may antioxidants be added to otic drug delivery?

Improve product stability - dependant on drug/vehicle choice 

What is the usual pH for otic drug solutions?

Usually acidic - pH of 3-4 which inhibits bacterial growth - favoured over viscosity modifiers