Contact the veterinarian if the pet has abdominal pain, tenderness, or discomfort; bloody, black or tarry stools or blood in vomit; unexplained weight gain; water retention; fatigue or lethargy; skin rash; itching; yellowing of eyes; unusual bruising or bleeding as these symptoms could indicate serious side effects. If any of the following serious side effects occur, stop giving Previcox and seek emergency veterinary medical attention; an allergic reaction (difficulty breathing; swelling of the lips; tongue or face; hives). Other less serious side effects may occur. Continue giving Previcox and talk to your veterinarian if your pet experiences flatulence or diarrhea; dizziness; headache; or insomnia. Other side effects may also occur. Talk to your veterinarian about any side effect that seems unusual or bothersome to your pet.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine .