The fine-thread method: lacrimation test for measuring ocular side-effects of drugs in the rat

Ocular toxicity of systemic asthma and allergy treatments

Systemic medications, such as antihistaminic and anti-inflammatory agents used in the treatment of asthma and allergy, may have adverse effects on the eye. The major adverse effects on the eye have included cataracts, glaucoma, and tear-film dysfunction (dry-eye syndrome). The use of inhaled corticosteroids (bronchial and nasal) has been associated with mild systemic effects when compared with oral corticosteroids. The development of cataracts and glaucoma has been more commonly associated with earlier "hard" oral and inhaled steroids that affected individuals with an inherent high susceptibility or those who used them for several years. Whereas oral antihistamines commonly have an effect on allergies within hours, they also may exacerbate dry-eye complaints that commonly complicate symptoms with various forms of tear film dysfunction or conjunctival hyperreactivity. Clinicians should be aware that other systemic agents may complicate their attempts to maximize the treatment of ocular allergies.

Effect of acetazolamide (Diamox) on tear secretion

The side effects of acetazolamide (Diamox) on lacrimation were measured in rats by means of the cotton-thread tear test. After a daily oral 1-mg dose (administered for five days), comparable to the dose used for adult humans on a drug-to-bodyweight basis, tear production remained unaffected but the lacrimal peroxidase secretion decreased by 60% of the baseline level. After withdrawal of acetazolamide the peroxidase secretion returned to the baseline level.

Cotton-thread tear test: an experimental study for testing drugs suspected of side effects on lacrimation

We tested tear fluid production and lacrimal peroxidase secretion in rats without and with drug consumption with the cotton-thread tear test. Twelve frequently prescribed drugs in patients were given in recommended therapeutic and excessive doses to rats. Daily oral doses during five days of Sudafed Plus (chlorpheniramine/pseudoephedrine combination), promethazine, atropine, timolol, aspirin, diazepam and furosemide equivalent to the doses used for adult humans on a drug-to-body-weight basis or excessive doses, resulted in about 20-60% reduction of tearing. Changes in lacrimal peroxidase secretion were found after administration of atropine, aspirin, furosemide, indomethacine and pilocarpine. Generally, tear production and lacrimal peroxidase secretion returned to baseline levels after withdrawal of the drugs.