Ammonium chloride is used off label and given by mouth to treat metabolic alkalosis, struvite stones, and certain toxicities occasionally in small animals and more often in large animals. The most common side effects include pain at the injection site or stomach upset if given by mouth. Do not use in pets with severe liver, kidney, heart, or lung disease. If a negative reaction occurs, please call your veterinary office.

Amlodipine is given by mouth and is used on and off label to treat high blood pressure in cats and dogs. Common side effects include vomiting, diarrhea, lack of appetite, sleepiness, or gingival (gum) overgrowth. Do not use in pets that are allergic to it, are in shock, have aortic stenosis, or are in liver failure. If a negative reaction occurs, please call your veterinary office.

Amitriptyline is used off label and given by mouth to treat behavioral and pain disorders in dogs, cats, and occasionally birds. Common side effects include sedation, dry mouth, constipation, and urinary retention. This medication should not be used in pets sensitive to TCAs, seizures, or pets currently using MOIs or flea collars. If a negative reaction occurs, call your veterinary office.

Amitraz is a topical solution in the form of a medicated dip, spot-on treatment, or collar used to treat demodectic mange or for the prevention of flea and tick infestations. Common side effects include sedation, incoordination while walking, slow heart rate, gastrointestinal effects, skin irritation, and temporary high blood sugar. This medication is contraindicated in very young animals, and used with caution in old, debilitated, diabetic, or small-breeds. While animals may exhibit signs of sedation, contact your veterinary office if your pet cannot be aroused from sleep or if the sedation lasts for more than 72 hours. Amitraz is toxic if swallowed.

Amantadine is an antiviral medication given by mouth in the form of a tablet, capsule, or liquid, that is mainly used off label for its pain control effects in pets. Common side effects include agitation and gastrointestinal effects. It should not be used in pets that are allergic to it, or that have untreated glaucoma. It should be used with caution in pets with liver, kidney, or heart disease, or in pets with eczema or seizures. If a negative reaction occurs, please call your veterinary office.