TETRACYCLINE HCL

Chemistry - An antibiotic obtained from Streptomyces aureofaciens, or derived semisyntheticallyfrom oxytetracycline, tetracycline HCl occurs as a moderately hygroscopic, yellow, crystallinepowder. About 100 mg/ml is soluble in water and 10 mg/ml soluble in alcohol. Tetracycline basehas a solubility of about 0.4 mg per ml of water and 20 mg per ml of alcohol. Commerciallyavailable tetracycline HCl for IM injection also contains magnesium chloride, procaine HCl andascorbic acid.

Storage, Stability, Compatibility

Unless otherwise instructed by the manufacturer, tetracyclineoral tablets and capsules should be stored in tight, light resistant containers at room temperature(15-30°C). The oral suspension and powder for injection should be stored at room temperature.
Avoid freezing the oral suspension.
After reconstituting the IM product, it may be stored at room temperature but should be usedwithin 24 hours of reconstitution. After reconstituting the intravenous product with sterile water to aconcentration of 50 mg/ml, the preparation is stable for 12 hours at room temperature. If furtherdiluted in an appropriate IV fluid, use immediately.
Tetracycline HCl for intravenous injection is reportedly compatible with the following IV fluidsand drugs: 0.9% sodium chloride, D5W, D5W in normal saline, Ringer's injection, lactated
Ringer's injection, 10% invert sugar, dextrose-Ringer's and lactated Ringer's combinations, ascorbic acid, cimetidine HCl, colistimethate sodium, corticotropin, ephedrine sulfate, isoproterenol
HCl, kanamycin sulfate, lidocaine HCl, metaraminol bitartrate, norepinephrine bitartrate, oxytetracycline HCl, oxytocin, potassium chloride, prednisolone sodium phosphate, procaine HCl, promazine HCl, and vitamin B complex with C.
Drugs that are reportedly incompatible with tetracycline, data conflicts, or compatibility isconcentration/time dependent, include: amikacin sulfate, aminophylline, ampicillin sodium, amobarbital sodium, amphotericin B, calcium chloride/gluconate, carbenicillin disodium, cephalothinsodium, cephapirin sodium, chloramphenicol sodium succinate, dimenhydrinate, erythromycingluceptate/lactobionate, heparin sodium, hydrocortisone sodium succinate, meperidine HCl, morphine sulfate, methicillin sodium, methohexital sodium, methyldopate HCl, oxacillin sodium, penicillin G potassium/sodium, phenobarbital sodium, sodium bicarbonate, thiopental sodium, andwarfarin sodium. Compatibility is dependent upon factors such as pH, concentration, temperatureand diluents used. It is suggested to consult specialized references for more specific information(e.g., Handbook on Injectable Drugs by Trissel; see bibliography).
Pharmacology/Uses, Indications - Refer to the oxytetracycline monograph just preceding this onefor information for tetracycline.

Pharmacokinetics - TETRACYCLINE HCL

Both oxytetracycline and tetracycline are readily absorbed after oral administration to fasting animals. Bioavailabilities are approximately 60-80%. The presence of food ordairy products can significantly reduce the amount of tetracycline absorbed, with reductions of 50%or more possible. After IM administration, tetracycline is erratically and poorly absorbed withserum levels usually lower than those attainable with oral therapy.
Tetracyclines as a class, are widely distributed to heart, kidney, lungs, muscle, pleural fluid, bronchial secretions, sputum, bile, saliva, urine, synovial fluid, ascitic fluid, and aqueous and vitreoushumor. Only small quantities of tetracycline and oxytetracycline are distributed to the CSF, andtherapeutic levels may not be achievable. While all tetracyclines distribute to the prostate and eye, doxycycline or minocycline penetrate better into these and most other tissues. Tetracyclines crossthe placenta, enter fetal circulation and are distributed into milk. The volume of distribution oftetracycline is approximately 1.2 - 1.3 L/kg in small animals. The amount of plasma protein bindingis about 20 - 67% for tetracycline.
Both oxytetracycline and tetracycline are eliminated unchanged primarily via glomerular filtration.
Patients with impaired renal function can have prolonged elimination half-lives and may accumulatethe drug with repeated dosing. These drugs apparently are not metabolized, but are excreted into the
GI tract via both biliary and nonbiliary routes and may become inactive after chelation with fecalmaterials. The elimination half-life of tetracycline is approximately 5-6 hours in dogs and cats.
Contraindications, Precautions, Reproductive Safety/
Adverse Effects, Warnings/ Overdosage, Acute Toxicity/Drug Interactions/-Drug-Laboratory Interactions - Refer to the oxytetracycline monograph preceding this one for information for tetracycline.