How Do Ophthalmic Quinolones Work?

Ophthalmic quinolones are broad-spectrum antibiotic medications used to treat bacterial eye infections. Ophthalmic quinolones kill bacteria by preventing DNA synthesis and replication in bacterial cells. Ophthalmic quinolones work by inhibiting the activity of two enzymes known as type II topoisomerases in the bacterial cell.

The two bacterial topoisomerase enzymes, gyrase and topoisomerase IV, play essential roles in bacterial DNA replication. The enzymes break the DNA strands, remove knots, repair and recombine them to make perfect copies of the bacterial DNA.

Ophthalmic quinolones are referred to as topoisomerase poisons, because they use the DNA-breaking characteristic of gyrase and topoisomerase IV and convert them into cellular toxins, effectively killing the bacteria. Ophthalmic quinolones bind to the broken ends of the DNA strands and block the topoisomerases from recombining them. Ophthalmic quinolones:

• Prevent relaxation of the supercoiled DNA
• Prevent removal of knots and tangles in the DNA
• Promote breakage of DNA strands
• Prevent repair and recombination of DNA strands

Ophthalmic quinolones are effective against both gram-positive and gram-negative bacteria including mycobacteria and anaerobic bacteria which thrive in low oxygen conditions. The emergence of quinolone-resistant bacterial strains, however, is a matter of growing concern, globally.

Gram-positive and gram-negative bacteria are structurally different and are classified depending on whether they get stained or not by a violet dye used in laboratory tests known as the Gram stain test. Ophthalmic quinolones are used to treat eye infections caused by susceptible strains of bacteria such as:

• Haemophilus influenzae
• Staphylococcus aureus
• Staphylococcus epidermidis
• Streptococcus mitis group
• Streptococcus oralis
• Streptococcus pneumoniae

Ophthalmic quinolones are solutions or ointments topically administered on the surface of the eye to treat the following conditions caused by bacterial infections:

• Bacterial conjunctivitis: Inflammation of the conjunctiva, the clear membrane over the whites of the eye and the inner surface of eyelids
• Corneal ulcers (keratitis): Inflammation and ulcers in the cornea
• Blepharitis: Inflammation of the eyelids
• Meibomianitis: Inflammation of the oil-producing Meibomian glands in the eyelids
• Dacryocystitis: Inflammation of the lacrimal sac, a part of the tear drainage system

Side effects of ophthalmic quinolones may include:

Ocular side effects

• Blurred vision
• Conjunctival redness
• Eye irritation and discomfort
• Eye pain
• Eye itching (pruritus)
• Burning and stinging
• Quinolone-associated corneal deposits (precipitates)
• Conjunctival hyperemia (dilation of blood vessels in the conjunctiva)
• Crystal or scales on eyelashes
• Foreign body sensation
• Inflammation of the cornea (keratitis)
• Degeneration of cornea (keratopathy)
• Chemical conjunctivitis or keratitis
• Damage to corneal epithelial cells
• Eyelid margin crusting
• Corneal infiltrates (collection of inflammatory cells)
• Corneal staining
• Corneal edema
• Reduced visual acuity
• Eyelid edema
• Light sensitivity
• Tearing and discharge
• Hypersensitivity reactions
• Growth of quinolone-resistant organisms with prolonged use
• Conjunctival irritation
• Papillary conjunctivitis (conjunctivitis with small round bumps known as papillae)
• Conjunctival or subconjunctival hemorrhage (bleeding in the conjunctiva)
• Conjunctival edema (chemosis)
• Dry eye
• Red eye
• Inflammation of the eyelid (blepharitis)
• Hemorrhagic conjunctivitis with eyelid (palpebral) edema (rare)

Systemic side effects

• Headache
• Unpleasant taste
• Hypersensitivity reactions such as:
• Itching, rash and hives
• Allergic dermatitis
• Angioedema (swelling in the tissue below the skin or mucous membranes such as facial, oral or pharyngeal edema)
• Shortness of breath (dyspnea)
• Nausea
• Fever
• Inflammation of the pharynx (pharyngitis)
• Inflammation of the nasal passage (rhinitis)
• Increased cough
• Middle ear inflammation (otitis media)
• Infection

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of some ophthalmic quinolones include:

• Besifloxacin hydrochloride ophthalmic (Besivance)
• Ciprofloxacin hydrochloride ophthalmic (Ciloxan)
• Gatifloxacin ophthalmic (Zymar, Zymaxid)
• Levofloxacin ophthalmic
• Moxifloxacin hydrochloride ophthalmic (Vigamox, Moxeza)
• Ofloxacin ophthalmic (Ocuflox)