Benadryl and Pepcid should be given for as long as your doctor instructs. This may be for a week, 6 months, 1 year, or indefinitely. These drugs rarely cause side effects. If you have questions or concerns about this, please discuss it with your oncologist.
Why do I need to give it?
Benadryl (diphenhydramine) and Pepcid (famotidine) are both anti-histamines. They block the action of histamines in the stomach—Pepcid, and systemically—Benadryl. Mast cell tumors have granules in them and these granules contain histamine amongst other chemicals. These medications are given to try to prevent side effects from excessive histamine release from the mast cell tumors.
How is it given?
Both medications are given orally.
What happens if I don't give it?
In most cases, your pet will be fine, but if you forget to give it for an extended period of time, please contact your veterinarian.
When does the drug start to work?
Both of these drugs start working immediately.
Where can I get these medications?
Both of these drugs can be purchased over the counter, meaning you do not need a prescription for them. Your veterinarian will write down the dosage for you and you can purchase these drugs at your local drug store (CVS, Walgreens, Wal-Mart, Costco, Rite-Aid, etc.)