APPENDIX B DRUG FORMULARY 759
Chloramphenicol andchloramphenicolpalmitate(Chloromycetin,generic forms)
Antibacterial drug.Mechanism of action is viainhibition of proteinsynthesis via binding toribosome. Broad spectrumof activity.
Bone marrow suppressionis possible with high dosesor prolonged treatment(especially in cats). Avoiduse in pregnant orneonatal animals.
Druginteractionswith otherdrugs (e.g., barbiturates)possible becausechloramphenicol willinhibit hepatic microsomalenzymes.Chloramphenicolpalmitate requires activeenzymes and should notbe administered to fasted(or anorectic) animals.Note:
Some forms ofchloramphenicol are nolonger available in the US.30 mg/mL oralsuspension(palmitate), 250 mgcapsules, and 100,250, and 500 mgtablets.
Dog: 40–50 mg/kg q8hpo.Cat: 50 mg/cat q12h po or12.5–20 mg/kg q12h po.
Chlorpheniraminemaleate(Chlor-Trimeton,Phenetron, and others)Antihistamine (H1blocker). Blocks action ofhistamine on receptors.Also may have directantiinflammatory action.Used most often toprevent allergic reactions.Used for pruritus therapyin dogs and cats.Sedation is most commonside effect. Antimuscariniceffects (atropine-likeeffects) also are common.Chlorpheniramine isincluded as ingredient inmany OTC cough/coldand allergy medications.4, 8 mg tablets.Dog: 4–8 mg/dog q12hpo(uptoamaximumof0.5 mg/kg q12h).Cat: 2 mg/cat q12h po.Cimetidine (Tagamet[OTC and prescription])Histamine-2 antagonist(H2 blocker). Blockshistamine stimulation ofgastric parietal cells todecrease gastric acidsecretion. Used to treatulcers and gastritis.Adverse effects usuallyseen only with decreasedrenal clearance. In people,CNS signs may occur withhigh doses.Druginteractions:May increaseconcentrations of otherdrugs used concurrently(e.g., theophylline)because of inhibition ofhepatic enzymes.Precise doses needed totreat ulcers have not beenestablished.100, 200, 300, 400,800 mg tablets;60 mg/mL oralsolution; 6 mg/mLinjection.10 mg/kg q6–8h IV, IM,po (in renal failure,administer 2.5–5 mg/kgq12h IV, po).(continued)