Modes
- 1. Topic instillation into the conjunctival
- Eye drops= most common and simplest , immediate action but is quickly diluted and
- Eye ointment: increases availability as it is longer in contact with the tissue as it is broken down slower but it blurs vision thus best for bed time
- Gels= prolonged contact, less blurry ; costly &difficult to prepare
- Ocusters=drug deliver across membrane placed in upper or lower fornix and lasts up to a week such as pilocarpine controlling long term primary open-angle glaucoma by keeping IOP low constantly
- Soft contact lenses = very good for delivering high concentration of drugs in emergency treatment e.g. pilocarpine and also for antibiotics and antiviral drugs in patients with corneal ulcers
They all mainly work by penetration through the cornea which has two important and relevant layers a lipophilic outer layer (epithelium) and a hydrophilic endothelium hence non polar bass through the first easily while polar done but the opposite is the case for the endothelium.
Thus the best drugs are the ones that are soluble in both or a prodrug that is lipophilic first and then become hydrophilic.