Oxytetracycline calcium

Oxytetracycline occurs as yellow crystals or crystalline powder, has a bitter taste and is odorless. Oxytetracycline hydrochloride should have potency not less than 835 pg C22H24N2O9 per mg [1], whilst for oxytetracycline not less than 832 pg/g [1] or 95.0-102.0% as anhydrous substance [2] or not less than 88.0% of C22H24N2O9 calculated as anhydrous basis [3,4]. For oxytetracycline calcium, it should contain not less than 90.0% and not more than 100.5% [2], or 865 pg C22H24N2O9 per mg [1]. Oxytetracycline was produced by the growth of certain strain of Streptomyces rimosus or obtained by other means. 

Two identification tests for oxytetracycline hydrochloride are given in the USP 28 [1], one being an ultraviolet absorption test and the other a color test. European Pharmacopoeia [2], British Pharmacopoeia (BP) 2003 [4], International Pharmacopoeia [5], and Pharmacopoeia of the People s Republic of China [6] described a thin-layer chromatography and color tests for identification of oxytetracycline hydrochloride and oxytetracycline dihydrate. For identification of oxytetracycline calcium, USP 28 [1] used Method II under identification of tetracycline <193>, whilst BP 2003 [4] described a TLC, color test, and calcium test as the method of identification. 

A light to deep red color is produced when oxytetracycline hydrochloride, oxytetracycline dihydrate, or oxytetracycline calcium is dissolved in sulfuric acid [1-5], and the color becomes yellow after water is added to the solution [1,2,4-7]. 

Another set of conditions in which suspensions are recommended include those drugs that are chemically unstable when in soluble form (they can easily hydrolyze this is the case of, for example, oxytetracycline calcium salts see Ref. 9), or in which large specific surface areas are required. Let us mention, for instance, antacid or absorbent compounds, or radiological contrasts (8). As already discussed (sec Table I), suspending media need not be alway.s aqueous hence suspensions can still be used even with drugs that can degrade in aqueous solution. For example, fenoxymethylpenicillin can be dispersed in coconut oil to be administered as an oral suspension (8). 

Oxytetracycline can also be employed at low pH on calcium-containing layers [35]. 

Oxytetracycline and doxycycline are used in horses. Oxytetracycline is the drug of choice for Potomac horse fever, caused by Ehrlichia risticii, and equine ehrlichiosis, caused by Ehrlichia equi. It is also used to treat contracted flexor tendons in foals, where the effects may be caused by calcium chelation at the myotendinous junction resulting in the relaxation of the flexor tendons. Some clinicians use parenteral oxytetracycline or p.o. doxycycline to treat horses with EPM. 

The tetracyclines are amphoteric antimicrobial agents that can form salts with bases or acids (see Chs 1 and 2). Oxytetracycline is a bitter, yellow, odorless crystalline powder. The base is slightly water soluble and the hydrochloride is readily water soluble and is typically administered to horses by slow i.v. injection. It is effective at 5.5 mg/kg once daily for 2 days or more in the treatment of B. equi but is unlikely to completely clear this infection. It is, therefore, used for premunition. Rapid i.v. injection may cause a precipitous drop in blood pressure and collapse owing to the effects of calcium chelation on the myocardium. Intramuscular injection causes objectionable local reactions in horses and should be avoided. Oral administration may be more... 

The absorption of tetracyclines from the G1 tract is non-uniform. Up to 30% of chlortetracycline is absorbed. The absorption for tetracycline, oxytetracycline, and demeclo-cycline ranges between 60 and 80%, whereas as much as 90 to 100% of doxycycline and minocycline is absorbed. The absorption of tetracyclines is impaired by divalent cations (calcium, magnesium, and ferrous iron), by aluminum, and by extremely alkaline pHs. Tetracyclines are distributed widely throughout the body fluid, cross the placental barrier, and can accumulate in growing bones. The concentrations of chlortetracycline in spinal fluid are only one fourth of those in plasma. Minocycline, a more lipid-soluble tetracycline, reaches a high concentration in tears and saliva and can eradicate the meningococcal carrier state. The tetracyclines are metabolized in the liver and excreted mainly by the bile and urine. The concentrations of tetracyclines in the bile are ten times higher than those in serum. 

Concomitant use of tetracycline with antacids containing aluminum, calcium, or magnesium decreases absorption of oxytetracycline (because of chelation) concomitant use with food, milk or other dairy products, oral iron products, or sodium bicarbonate also impairs oral absorption. 

As tetracyclines have moderate to high lipophilic properties, the poor bioavailability associated with oral administration is somewhat surprising. Papich and Riviere suggest that causes may be multifactorial. As zwitterions, they are mainly ionized at pHs within GIT liquor. Moreover, feed reduces bioavailability, and tetracyclines chelate with polyvalent cations. Oxytetracycline absorption has been shown, experimentally, to be reduced by feed, dairy products, Ca +, Mg +, Al +, and Fe + ions and antacids. Even though doxycycline has a similar structure, affinity for metals is different from that of oxytetracycline with greater affinity for zinc and less for calcium. 

Terra Aiba 1, Terra Aiba F P, Terra alba Terra Aiba. See Calcium sulfate dihydrate Terracur P. See Fensulfothion Terra-Dry Freeze Dried Aioe Vera Powd. 100X. See Aloe barbadensis gel Terra japonica. See Black catechu Terramycin hydrochloride. See Oxytetracycline hydrochloride... 

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