Melengestrol is a steroidal progestin and antineoplastic agent which was never marketed. An acylated derivative, melengestrol acetate, is used as a growth promoter in animals. Melengestrol acetate (MGA) is one of six steroidal hormone growth promoters approved for use in Canada and USA. These products are used to improve growth rate and feed efficiency, as well as to suppress estrus in beef heifers (CFIA 2008). They are not approved for use in any species other than beef cattle meant for slaughter. MGA is the only drug of its kind that is administered in animal feed, and its labelled dose in Canada is 0.4mg per heifer per day (CFIA 2008). A mandatory withdrawal of 2 days before slaughter is applied to any animal that is administered MGA.

Deslorelin is an GnRH agonist used in veterinary. It effects contraception by temporarily suppressing the reproductive endocrine system and preventing production of pituitary (FSH and LH) and gonadal hormones (estradiol and progesterone in females and testosterone in males). The observed effects are similar to those following ovariectomy or castration, but are reversed after the hormone content of the implant is depleted or the implant is removed. As an agonist, deslorelin first stimulates the reproductive system, which can result in estrus and ovulation in females or temporary enhancement of testosterone and semen production in males. Then, down-regulation follows the initial period of stimulation. Although deslorelin can also be an effective contraceptive in males of some species, manufacturer recommends its use primarily in females, since monitoring efficacy in females by suppression of estrous behavior or of gonadal steroids in feces is more straightforward than ensuring continued absence of sperm in males, since most institutions cannot perform regular semen collections. It can, however, be used to ameliorate aggression in males of some species, but higher dosages are usually needed. While the major application of deslorelin was initially male contraception, due to its two differing actions, either the stimulation of oestrus or the sterilization of fertility, its use has been increasing in the bitch as well. SUPRELORIN® F (deslorelin acetate) Implant is a once-yearly, subcutaneous implant that assists in the management of adrenal disease in ferrets.

Nifurpipone is a nitrofuran with a large antimicrobial spectrum. Nifurpipone was shown to be a useful antibacterial agent in urinary tract infections.

Ornithine is an amino acid produced in the urea cycle by the splitting off of urea from arginine. It is a central part of the urea cycle, which allows for the disposal of excess nitrogen. Ornithine is also a precursor of citrulline and arginine. Arginine stimulates the pituitary release of growth hormone. Burns or other injuries affect the state of arginine in tissues throughout the body. As de novo synthesis of arginine during these conditions is usually not sufficient for normal immune function, nor for normal protein synthesis, ornithine may have immunomodulatory and wound-healing activities under these conditions (by virtue of its metabolism to arginine).

Enzacamene, ( )-[Bicyclo[2.2.1]-heptan-2-one, 1,7,7-trimethyl-3-[(4-methylphenyl)methylene]-, (1R,3E,4S)-] is one of enantiomer of Enzacamene (4-MBC) -- organic sunscreen components, that protects against UV radiation and may therefore help in the prevention of skin cancer. Enzacamene can exist as a cis-(Z)- and trans-(E)-isomer due to the exocyclic carbon-carbon (styrene) double bond. A commercial Enzacamene from a major supplier of UV filters showed the presence of only the (E)-isomer However, it is known that, upon exposure to light, (E)-4-Enzacamene is photochemically isomerized reversably to (Z)-4-Enzacamene. Both (E)- and (Z)-Enzacamene are chiral and thus consist of enantiomers (optical isomers). In a technical material and in a major brand sun lotion, Enzacamene was shown to consist entirely (>99%) of (E)-isomers and to be racemic. Wastewater showed the presence of both (E)- and (Z)-Enzacamene with a clear excess of (E)-isomers (E >Z). Untreated wastewater showed a nearly racemic composition suggesting that most if not all commercial Enzacamene is racemic. Treated wastewater indicated some excess of (R)- or (S)-stereoisomers ikely as a result of some enantioselective (bio)degradation in wastewater treatment plants. Enantiomers may show different biological behavior with respect to uptake, metabolism, and excretion and often differ in toxicity and other biological effects.

Ornithine is an amino acid produced in the urea cycle by the splitting off of urea from arginine. It is a central part of the urea cycle, which allows for the disposal of excess nitrogen. Ornithine is also a precursor of citrulline and arginine. Arginine stimulates the pituitary release of growth hormone. Burns or other injuries affect the state of arginine in tissues throughout the body. As de novo synthesis of arginine during these conditions is usually not sufficient for normal immune function, nor for normal protein synthesis, ornithine may have immunomodulatory and wound-healing activities under these conditions (by virtue of its metabolism to arginine).

Tiamulin is a diterpene antimicrobial with a pleuromutilin chemical structure similar to that of valnemulin. The activity of tiamulin is largely confined to gram-positive micro-organisms and mycoplasma. Tiamulin acts by inhibiting protein synthesis at the ribosomal level. In veterinary medicine, tiamulin is used for treatment and prophylaxis of dysentery, pneumonia and mycoplasmal infections in pigs and poultry. Tiamulin is available as a 2, 10 or 20% premix for pigs and poultry, a 12.5% solution or 45% water soluble powder for addition to drinking water for pigs and poultry, or a 10% injectable formulation for pigs. Tiamulin inhibits protein synthesis by targeting the 50S bacterial ribosomal subunit and binding to peptidyl transferase, the enzyme responsible for forming peptide bonds between amino acids.

Tilmicosin is a macrolide antibiotic was prepared by chemical modifications of desmycosin, and is used in veterinary. It is recommended for treatment and prevention of pneumonia in cattle, sheep and pigs, associated with Pasteurella haemolytica, P. multocida, Actinobacillus pleuropneumoniae, mycoplasma species and other microorganisms found sensitive to this compound. Tilmicosin belongs to 16-membered ring group of class macrolides. The antimicrobial mechanism seems to be the same for all of the macrolides. They interfere with protein synthesis by reversibly binding to the 50S subunit of the ribosome. They appear to bind at the donor site, thus preventing the translocation necessary to keep the peptide chain growing. The effect is essentially confined to rapidly dividing bacteria and mycoplasmas. Macrolides are regarded as being bacteriostatic but demonstrate bactericidal activity at high concentrations.

Domperidone is a peripherally selective D2 receptor antagonist. It acts as an antiemetic and a prokinetic agent through its effects on the chemoreceptor trigger zone and motor function of the stomach and small intestine. Domperidone was not approved in USA due to risks of cardiac arrhythmias, cardiac arrest, and sudden death, but is available in other countries. However, FDA allows access to Domperidone through an expanded access investigational new drug application (IND) to patients with gastroesophageal reflux disease with upper GI symptoms, gastroparesis, and chronic constipation. As an “off-label” use, domperidone is prescribed to breastfeeding women to enhance their milk production.