Side Effects

Most of the significant side effects of the OBBs are thought to be explained by beta blockade. While not every adverse effect has been reported with every drug, this discussion does not associate specific events with specific drugs unless there is a unique relationship reported between one drug and the effect.

3.6.1 Local Adverse Effects. Corneal anesthesia was a significant adverse effect associated with topical propranolol. No significant corneal anesthesia effect has been observed with current OBBs in the majority of patients.14 However, individual patients can have a significant corneal anesthesia effect that may exacerbate existing ocular surface disease.15,16

Discomfort upon instillation (burning and stinging) is an adverse effect associated with every drug used to lower IOP. This effect is a function of several factors: active molecule, pH, preservative, and vehicle. There has been a higher incidence of transient discomfort associated with betaxolol solution and with metipranolol than with timolol.17-19 The betaxolol suspension appears to be better tolerated than the solution.20

Almost all OBBs have benzalkonium chloride (BAK) as their preservative (table 3.1). Sensitivity to BAK is not uncommon. Patients may become symptomatic, particularly if they are taking multiple medications with BAK. The branded preparations of carteolol, levobunolol, and metipranolol have lower concentrations of BAK than do branded betaxolol and timolol maleate solution. Timolol maleate is available without preservatives. Timoptic-XE has benzododecinium bromide as a preservative. An awareness of the preservatives may help the clinician choose a tolerable OBB for the BAK-sensitive patient.

Timolol use has been associated with decreased tear production and decreased goblet cell density.21,22 These alterations may result in dry eye symptoms. Use of

Table 3.1 Available Ophthalmic Beta-Blockers

Drug Comment Concentration (%) Supplied (mL) Preservative

Table 3.1 Available Ophthalmic Beta-Blockers

Drug Comment Concentration (%) Supplied (mL) Preservative

Timolol

Maleate generic

0.25,

0 0

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