Methacycline hydrochloride

Litchman and Upton [192] reported the determination of triethyla-mine in streptomycin sulfate and in methacycline hydrochloride to levels as low as 0.05%. A weighed sample was treated with 1M sodium hydroxide solution at 60°C for 1 hr. A headspace sample was manually withdrawn and analyzed on a polystyrene column at 160°C using a flame-ionization detector. The levels of triethylamine found ranged from 0.15% to 0.36% for streptomycin sulfate and from 0.06% to 0.13% for methacycline hydrochloride. Recoveries were better than 94%. The precision of the determination, based on five replicate weighings of sample, was 2% for streptomycin sulfate and 5% for methacycline hydrochloride. 

Ametazole Hydrochloride Benzthiazide Chlordiazepoxide Dichlorphenamide Hydroxychloroquine Sulphate Methacycline Hydrochloride Phentolamine Hydrochloride Acetarsol... 

Hydrogen was introduced into a standard hydrogenation vessel containing 10 grams 6-deoxy-6-demethyl-6-methylene-5-oxytetracycline hydrochloride (methacycline), 150 ml methanol and 5 grams 5% rhodium on carbon. The pressure was maintained at 50 psi while agitating at room temperature for 24 hours. The catalyst was then filtered off, the cake washed with methanol and the combined filtrates were evaporated to dryness. The dry solids were slurried in ether, filtered and the cake dried. The resulting solids exhibited a bioactivity of 1,345 units per mg versus K. pneumoniae. 

The oral dosage for rapidly excreted tetracyclines, equivalent to tetracycline hydrochloride, is 0.25-0.5 g four times daily for adults and 20-40 mg/kg/d for children (8 years of age and older). For severe systemic infections, the higher dosage is indicated, at least for the first few days. The daily dose is 600 mg for demeclocycline or methacycline, 100 mg once or twice daily for doxycycline, and 100 mg twice daily for minocycline. Doxycycline is the oral tetracycline of choice because it can be given as a once-daily dose and its absorption is not significantly affected by food. All tetracyclines chelate with metals, and none should be orally administered with milk, antacids, or ferrous sulfate. To avoid deposition in growing bones or teeth, tetracyclines should be avoided in pregnant women and children less than 8 years of age. 

Miyazaki, S. Nakano, M. Arita, T. A comparison of bioavailability of free bases and hydrochloride salts of chlorte-tracycline, demethylchlortetracycline, and methacycline. 

Dmgs, as we have seen, must be in their molecular form before diffusional absorption processes take place. We would expect bases to be more soluble than acids in the stomach, but it is impossible to generalise in this way. Although the basic form of a dmg as its hydrochloride salt should be soluble to some extent in this medium, this is not always so. Indeed the free bases of, for example, chlor-tetracycline, dimethylchlortetracycline and methacycline are more soluble than their corresponding hydrochlorides in the pH range... 

---