Potential Side Effects of Commonly Prescribed Medications

Antibiotics

Side effects tend to be uncommon and mild. They usually involve GI upset (vomiting, diarrhea, poor appetite). Administering antibiotics with food can help.

Pain Relievers/Anti-inflammatories

Never give more than one NSAID at a time or an NSAID and a corticosteroid at the same time, this can cause bleeding GI ulcers.

Non-Steroidal Anti-Inflammatories NSAIDs:
Meloxicam (Meloxidyl, Ostilox, etc.) – GI distress most common (still rare), kidney toxicity is low, but cats should be given lower dose. Not FDA approved for chronic use in cats but is approved in virtually every other country.
Carprofen (Rimadyl) – GI distress most common (still rare), rarely can cause liver failure- monitor via bloodwork

Corticosteroids
Prednisone – increased thirst/urination, increased appetite, panting, behavioral changes
Prednisolone – same as prednisone
Temaril-P – same as prednisone, also drowsiness

Opioids
Tramadol – drowsiness, well-tolerated

Gastrointestinal

Bethanechol – vomiting, diarrhea, drooling, anorexia
Famotidine –GI side effects, headache, dry mouth
Lactulose – flatulence, distended stomach, cramping, diarrhea
Maropitant (Cerenia) –continued vomiting, drooling, diarrhea, anorexia
Metronidazole – Rarely neurologic toxicity (seizures, abnormal behavior)
Sucralfate – extremely safe

Behavioral

Combinations of these drugs need to be carefully chosen by a doctor as some combinations can cause serotonin syndrome.

Acepromazine – hypotension, high heart rate, low heart rate, hypothermia, hyperthermia
Clomipramine – lethargy, anorexia, vomiting, diarrhea, increased liver enzymes, dry mouth, increased heart rate
Fluoxetine – lethargy, seizures, GI effects, anxiety, irritability, insomnia/hyperactivity, panting, aggressive behavior, anorexia (usually transient)
Trazadone – sedation, lethargy, ataxia, abnormal heart rhythm, increased anxiety, aggression

Hormone-Related

Estriol (Incurin) – anorexia, vomiting, increased thirst
Insulin (any type) – hypoglycemia, hyperglycemia, insulin resistance
Levothyroxine (Thyrovet, Thyro-tabs) – none at correct dose- monitor via bloodwork
Methimazole – vomiting, anorexia, lethargy
Trilostane (Vetoryl) – lethargy, inappetence, vomiting, electrolyte abnormalities, diarrhea, all typically self-limiting

Cardiac/Blood Pressure

Enalapril – poor appetite, diarrhea, vomiting
Furosemide (Lasix) – electrolyte abnormalities, dehydration
Pimobendan (Vetmedin) – GI side effects, cardiac arrhythmia

Anti-Parasitics

Fenbendazole (Panacur) – allergic reactions from dying parasites, drooling, vomiting, diarrhea
Ivermectin – potentially fatal if patient has heartworms, neurotoxicity esp. in animals with MDR1 gene defect
Praziquantel – poor appetite, vomiting, lethargy, diarrhea
Pyrantel (Strongid) – vomiting
Sulfadimethoxine (Albon) – urinary issues, dry eye, bone marrow depression, skin rash, inflamed retina, fever, vomiting, polyarthritis

Anti-Itch/Allergies

Apoquel – diarrhea, vomiting, poor appetite, lethargy
Cyclosporine (Atopica) – vomiting, poor appetite, diarrhea

Anti-Convulsants

Gabapentin – sedation, ataxia
Leviteracetam – lethargy
Phenobarbital – increased agitation, lethargy, increased thirst, increased appetite, ataxia, increased liver enzymes, rarely anemia, low platelets, low white blood cells
Potassium Bromide – lethargy, increased appetite, increased thirst
Zonisamide – sedation, ataxia, inappetence

Miscellaneous

Albuterol – increased heart rate, tremors, nervousness, dizziness (all typically transient)
Azathioprine – bone marrow suppression, GI upset, anorexia, poor hair growth, acute pancreatitis, liver toxicity
Hydroxyzine – sedation, rarely tremors, seizures, depression, behavioral changes
Ketoconazole/Fluconazole/Itraconazole – inappetence, rarely increased liver enzymes, liver toxicity
Meclizine/Mirataz – sedation, dry mouth, dry eyes, increased heart rate
Methocarbamol – sedation, salivation, vomiting, lethargy, weakness, ataxia
Proin – restlessness, irritability, hypertension, anorexia
Terbinafine – vomiting