You may help to ease your pet's symptoms with the use of some over-the-counter medicines.  However, it's never a good idea to just assume a human medication will be a safe and effective treatment for your pet.  Contact your veterinarian before starting any medical therapy, to discuss your options.  Always let the veterinarian know your pet's symptoms and what you have been treating it with.  As with all illnesses, persistent symptoms warrant a trip to the doctor's office.
Acetaminophen(Tylenol) and Ibuprofen (Advil, Motrin IB) are toxic to both cats and dogs, even in small doses.  Many medications can be highly toxic to cats, including Pepto Bismol, Kaopectate and aspirin.

Here is a list of over-the-counter medications that can be safely used for your pet.  Please read everything before administering an OTC medication to your pet.  If it is not on this list -- do not give it!

IMODIUM (loperamide):
Can be given to some dogs and cats for diarrhea.  WARNING: Certain dog breeds related to Collies may have adverse reactions to Imodium (loperamide).  Do not give this medicine to Collies, Shelties, Australian Shephards and Long-haired Whippits. See this site for more detailed information.  (Thanks to Ken Brookner for this correction.)

For those animals for which this medicine is appropriate give 1 teaspoon for every 20 pounds.  This dosage can be repeated every 4-6 hours until symptoms begin to resolve, not to exceed 24 hours.

Can be administered to dogs (never cats!) with upset stomach or vomiting.  Give one teaspoon per 20 pounds of weight every 4-6 hours for 24 hours, or until symptoms begin to resolve.

Benadryl is an antihistamine that helps relieve swellings and itching from allergic reactions and is used long-term to treat allergies.  The dose is one milligram for every pound given twice daily.  (Although safe to use, Benadryl is not very effective in cats, and other antihistamines are more commonly prescribed.)

Benadryl Dosage
Twice daily
(1 mg per pound)
12 lbs12 milligrams
(pediatric dose)
25 lbs25 milligrams
(1 adult capsule)
50 lbs50 milligrams
(2 adult capsules)

Can be given short term to dogs (never cats!) to help relieve inflammation and pain.  Buffered Aspirin (Bufferin) is easier on the stomach but regular (non-coated) aspirin can also be used.  Aspirin may be given once or twice a day.  Always give aspirin with food.

Aspirin has potent blood thinning properties, and continued usage may be dangerous in some animals. For long term pain relief there are safer veterinary-specific alternatives.

Aspirin Dosage
Once or twice a day, with food
less than 10 lbs ½ baby aspirin   NEVER!  
10-30 lbs 1 baby aspirin
30-50 lbs ½ regular aspirin
50-100 lbs 1 regular aspirin
over 100 lbs 2 regular aspirin

DRAMAMINE (Dimenhydrinate):
Dramamine is an antihistamine that works well at preventing motion sickness in both cats and dogs.  This drug works best if given at least ½ hour prior to travel. 

Dramamine Dosage
½ hour prior to travel
small12.5 milligrams 12.5 milligrams
medium25 milligrams
large50 milligrams

TAGAMET (Cimetidine),  PEPCID-AC (Famotidine),  ZANTAC (Ranitidine):
Reduces the amount of stomach acids and can be dispensed to dogs and cats suffering from ulcers, acid reflux or belly ache. Sometimes they are used to prevent ulcers in animals taking other medications. These medications are given once to twice daily. It's best to discuss the exact dosage with your veterinarian.

Tagamet/Pepcid-AC/Zantac Dosage
one or twice daily
less than 20 lbs¼ tablet ¼ tablet
20-60 lbs½ tablet
over 60 lbs1 whole tablet

Can help to relieve itchy, raw or irritated skin. It can be used topically to reduce itching from hives, hot spots, and insect bites and stings. Apply a small amount up to two times daily.

GAS-X (Simethicone):
Simethicone is used in dogs to help with unusual flatulence or gas discomfort. Any dog suspected of Bloat should get 2 doses immediately before transport to the Emergency Clinic.

GAS-X Dosage
small¼ adult dose ¼ adult dose
medium½ adult dose
large1 adult dose

Glucosamine (and glucosamine in combination with chondroitin sulfate) is used to treat joint pain associated with arthritis. This is a long term treatment and its effects may not be immediately noticeable.

Glucosamine Dosage
total per day
under 25 lbs500 milligrams 500 milligrams
25-50 lbs1000 milligrams
over 50 lbs1500 milligrams

Are helpful in the treatment of small wounds, bites or minor infections.  Always thoroughly clean the wound with soap and water first.

Can be use to clean any wound or injury.

1 - 10 teaspoons given orally can be used to induce vomiting in dogs.  (See toxicities.)  Never induce vomiting unless being directed to by a veterinarian.  If you think that your pet may have ingested a potentially poisonous substance, call the Animal Poison Control Center at 888-426-4435.  Hydrogen peroxide is not as effective to clean wounds as antibacterial soap and water.

Saline nasal spray and pediatric nasal sprays (Little Noses) can be given in kittens, cats, puppies, and dogs to alleviate dryness and nasal congestion associated with a cold.  No other type of OTC nasal medication should be used unless prescribed by your veterinarian.