From the FDA Drug Label
Nausea, vomiting, dizziness, slurring of speech, blurring of vision, and visual hallucinations (including bright colors and strange designs) are among the early manifestations The vision side effects of Isoniazid (Isonicotinic Hydrazide) include:
- Blurring of vision
- Visual hallucinations, which may include seeing:
- Bright colors
- Strange designs There is no information in the provided drug label about vision side effects of Pyridoxine (Vitamin B6) when used in conjunction with Isoniazid 1.
From the Research
Isoniazid can cause vision problems, particularly optic neuritis, as a side effect, but vitamin B6 (pyridoxine) supplementation helps prevent this complication. When taking isoniazid for tuberculosis treatment or prevention, patients should take 25-50 mg of vitamin B6 daily to reduce the risk of neurological side effects, including vision changes. Isoniazid depletes pyridoxine in the body by forming hydrazones with pyridoxal phosphate, the active form of vitamin B6, which is essential for normal neurological function including visual pathways 2. Without adequate B6, patients may experience blurred vision, color vision changes, or even vision loss. These vision changes are typically reversible if caught early and if B6 supplementation is initiated. Certain populations are at higher risk for these side effects, including malnourished individuals, pregnant women, people with diabetes, HIV, alcoholism, or kidney disease.
Key Points to Consider
- The frequency of peripheral neuropathy, which can include vision problems, is higher among slow inactivators of isoniazid than among rapid inactivators 3.
- Pyridoxine supplementation has been shown to prevent peripheral neuropathy in patients receiving high-dosage isoniazid therapy 4, 5.
- A daily dose of 6 mg of pyridoxine has been found to be effective in preventing peripheral neuropathy in patients receiving high-dosage isoniazid therapy 5.
- Other vitamin B preparations, such as Tab. Aneurin. Co., have been found to be ineffective in preventing peripheral neuropathy 6.
Recommendations
- Patients taking isoniazid should receive pyridoxine supplementation to prevent neurological side effects, including vision changes.
- The recommended daily dose of pyridoxine is 25-50 mg.
- Patients should be monitored for signs of peripheral neuropathy, including vision changes, and should contact their healthcare provider immediately if any symptoms occur.