Clemastine fumarate should not be used in animals that are hypersensitive to it. Special care is required while administering this medication in animals with known prostate and bladder conditions, heart ailments and glaucoma. Extreme caution is needed while using this medicine on animals on sedatives or tranquilizers. Clemastine fumarate is thought to be safe for use in pregnant animals; however its traces will be present in mothers’ milk, so be cautious while using this medication in nursing pets. Overdose of this medication might result in dry mouth, blurred vision, rapid heart rate, urinary retention, fever and low pressure, which require urgent medical intervention.