What are the potential interactions with latanoprost (prostaglandin analogue)?

Latanoprost Drug Interactions

Latanoprost has minimal clinically significant drug interactions, with the primary concern being precipitation when mixed with thimerosal-containing eye drops, requiring 5-minute spacing between different topical ophthalmic medications. 1

Key Drug Interactions

Thimerosal-Containing Products

• In vitro studies demonstrate precipitation occurs when latanoprost is mixed with eye drops containing thimerosal, requiring administration at least 5 minutes apart 1
• This is the only documented chemical incompatibility with latanoprost 1

Multiple Topical Ophthalmic Medications

• All topical ophthalmic drugs should be administered at least 5 minutes apart to prevent washout and ensure proper absorption 2, 1
• This spacing applies to any combination therapy, including beta-blockers, carbonic anhydrase inhibitors, or other glaucoma medications 2, 1

Additive Therapeutic Effects (Not True Interactions)

Combination Therapy Benefits

• Latanoprost demonstrates significant additive IOP-lowering effects when combined with other glaucoma medications, particularly timolol 3, 4
• The fixed combination of latanoprost plus timolol provides superior IOP reduction compared to either component alone 3, 5
• Adding dorzolamide to latanoprost provides an additional 5.6% IOP reduction through complementary mechanisms 2

Contact Lens Considerations

• Latanoprost contains benzalkonium chloride, which is absorbed by contact lenses 1
• Contact lenses must be removed prior to administration and may be reinserted 15 minutes after instillation 5, 1

Clinical Cautions (Not Drug Interactions)

Conditions Requiring Careful Use

• Use with caution in aphakic patients, pseudophakic patients with torn posterior lens capsule, or those with known risk factors for macular edema, as cystoid macular edema has been reported 1, 6
• Avoid in patients with active uveitis due to the pro-inflammatory mode of action of prostaglandins 6
• Limited experience exists in angle closure, inflammatory, or neovascular glaucoma 1

Pregnancy and Lactation

• Pregnancy Category C rating; most ophthalmologists avoid prostaglandins during pregnancy due to theoretical risk of premature labor 3
• Unknown if excreted in human milk; caution advised during breastfeeding 1

Systemic Drug Interactions

• Latanoprost produces no systemic adverse effects and does not alter routine blood analyses because it is rapidly metabolized outside the eye 7, 8
• Unlike timolol, latanoprost lacks cardiopulmonary adverse effects, making it suitable for patients with contraindications to beta-blockers 4