Small Animal Dermatology, 3rd edition

APPENDIX B DRUG FORMULARY 793

Methotrexate (MTX,Mexate, Folex,Rheumatrex, andgeneric)

Anticancer agent. Usedfor various carcinomas,leukemia, andlymphomas. Action is viaantimetabolite action.Analogue of folic acidthat binds dihydrofolatereductase. Inhibits DNA,RNA, and proteinsynthesis. In people,methotrexate is alsocommonly used forautoimmune diseases,such as rheumatoidarthritis.

Anticancer drugs causepredictable (andsometimes unavoidable)side effects that includebone marrowsuppression, leukopenia,and immunosuppression.Hepatotoxicity has beenreported in people frommethotrexate therapy.Drug interactions

:

Concurrent use withNSAIDs may cause severemethotrexate toxicity. Donot administer withpyrimethamine,trimethoprim, orsulfonamides.

Use in animals has beenbased on experimentalstudies. There is onlylimited clinical informationavailable. Consult specificanticancer protocols forprecise dosage andregimen.

2.5 mg tablets; 2.5or 25 mg/mLinjection.

2.5–5 mg/m

2

q48h po

(dose depends on specificprotocol).Dog: 0.3–0.5 mg/kgonce/week IV.Cat: 0.8 mg/kg IV every2–3 weeks.

Methylprednisolone(Medrol)

Glucocorticoidantiinflammatory drug.Compared toprednisolone,methylprednisolone is1.25

×

more potent.

Same as for otherglucocorticoids.Manufacturer suggeststhat methylprednisolonecauses less PU/PD thanprednisolone.

Use ofmethylprednisolone issimilartothatofothercorticosteroids. Doseadjustment should bemade to account fordifference in potency (seedose section.)

1, 2, 4, 8, 18, 32 mgtablets.

0.22–0.44 mg/kgq12–24h po.

(continued

)