From the Guidelines
Tizanidine, melatonin, and prazosin can all potentially cause blurred vision as a side effect, though with varying frequencies. Tizanidine, a muscle relaxant, commonly causes blurred vision in many patients due to its effects on the central nervous system and its ability to lower blood pressure, as noted in the study 1. Prazosin, an alpha-blocker used for hypertension and PTSD-related nightmares, can cause blurred vision particularly when starting treatment or increasing doses because it reduces blood pressure which may temporarily decrease blood flow to the eyes, as seen in the guidelines 1. Melatonin, a sleep aid, less commonly causes blurred vision but some users report this effect, possibly due to its sedative properties affecting visual processing. Some key points to consider when prescribing these medications include:
- Monitoring blood pressure and adjusting doses as needed to minimize the risk of hypotension and subsequent blurred vision
- Being aware of the potential for blurred vision as a side effect and advising patients to report any visual disturbances
- Considering alternative medications or adjusting the timing of medication administration to minimize the impact of visual side effects on daily activities
- Regularly reviewing medication regimens in older adults to minimize the risk of polypharmacy and adverse drug reactions, as recommended in the review by the European Society of Cardiology Working Group on Cardiovascular Pharmacotherapy 1. If you experience persistent blurred vision while taking any of these medications, you should contact your healthcare provider promptly. The visual disturbances are typically temporary and resolve when the medication is discontinued or the dose is adjusted. For people who need these medications but experience vision problems, taking them at bedtime rather than during the day may help minimize the impact of visual side effects on daily activities.
From the FDA Drug Label
Adverse Events Reported in Controlled Studies ... Amblyopia (blurred vision) <1 3
- Tizanidine can cause blurred vision, as it is listed as amblyopia (blurred vision) in the adverse events reported in controlled studies, with an incidence of 3% in the tizanidine group compared to less than 1% in the placebo group 2.
- There is no information in the provided drug label about melatonin or prazosin.
- The FDA drug label does not answer the question for melatonin or prazosin.
From the Research
Tizanidine
- The most common adverse effects associated with tizanidine are dry mouth and somnolence/drowsiness 3
- There is no mention of blurred vision as a side effect of tizanidine in the provided studies 3, 4
Melatonin
- Melatonin is used to treat rapid eye movement sleep behavior disorder (RBD) 5
- There is no mention of blurred vision as a side effect of melatonin in the provided studies 5, 6, 7
Prazosin
- Prazosin is a centrally active alpha-1 adrenergic receptor antagonist used to treat posttraumatic stress disorder (PTSD) and RBD 5, 6, 7
- Prazosin can cause dizziness and lightheadedness, which may increase the risk of falls, but there is no direct mention of blurred vision as a side effect 6, 7
- However, it is worth noting that prazosin can cause orthostatic hypotension, which may lead to blurred vision in some cases, although this is not explicitly stated in the provided studies 6, 7