Drugs online research references
Agents Actions. 1985 Dec;17(2):229-42.
Metal ion-tetracycline interactions in biological fluids. Part 5. Formation of zinc complexes with tetracycline and some of its derivatives and assessment of their biological significance.
Brion M, Lambs L, Berthon G.
A series of studies was previously devoted to the dependence of the bioavailability of various tetracyclines on their coordination with calcium and magnesium ions. Several clinical investigations have also shown zinc to interfere with the gastrointestinal absorption of the drug in humans. On the other hand, the administration of tetracycline to rats was reported to result in the increase of the elimination rate of zinc, which could originate in zinc-tetracycline interactions in blood plasma. Formation constants for zinc complexes with tetracycline, oxytetracycline, doxycycline, minocycline, chlortetracycline and demethylchlortetracycline were thus determined at 37 degrees C in NaCl 0.15 mol. dm-3 aqueous medium. Computer simulations were then carried out to investigate the drug influence on the distribution of the low-molecular-weight fraction of zinc in human blood plasma. Zinc-tetracycline interactions in the gastrointestinal fluid were also simulated, using clinical data relative to fasting subjects as taken from the literature. No significant effect can be expected from tetracyclines on the distribution of zinc in plasma at the usual therapeutic levels. However, zinc-tetracycline interactions have been found to be determining factors for the bioavailabilities of the metal as well as of the antibiotic in the gastrointestinal fluid.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4096307&dopt=Abstract
Arch Oral Biol. 2000 Apr;45(4):257-65.
The effect of minocycline on the metabolism of androgens by human oral periosteal fibroblasts and its inhibition by finasteride.
Soory M, Tilakaratne A.
Department of Periodontology, GKT Dental Institute, King's College, Caldecot Road, London, UK.
The antimicrobial minocycline has matrix-stimulatory effects on connective tissue and bone. The aim here was to study the effect of minocycline on 5alpha reduction of androgen substrates to 5alpha-dihydrotestosterone (DHT) in periosteal fibroblasts and the influence of the antiandrogen finasteride on this conversion. Confluent cultures of periosteal fibroblasts established from oral periosteum isolated from the bone surface were incubated in duplicate in multiwell dishes with two androgen substrates, [(14)C]-testosterone/[(14)C]-4-androstenedione, in the presence or absence of serial concentrations of minocycline or the antiandrogen finasteride or the two in combination for 24 h. The metabolites formed were solvent-extracted with ethyl acetate, separated by thin-layer chromatography and quantified using a radioisotope scanner. Both androgen substrates were metabolized to DHT and 4-androstenedione or testosterone. Minocycline stimulated the synthesis of DHT from these substrates by 75-83% at 20-30 microg/ml (n=4; p<0.01). Finasteride inhibited the 5alpha-reductase activity of these substrates by 3-5-fold at 1 microg/ml and 40-80% at 0.01 and 0.1 microg/ml (n=4; p<0.01), with little change in 17beta-hydroxysteroid dehydrogenase activity. Minocycline and finasteride in combination showed an intermediate response with one substrate. As finasteride inhibits the type 2, 5alpha-reductase isoenzyme associated with anabolic functions, these findings demonstrate target-tissue androgen metabolic activity in periosteal fibroblasts at baseline and in response to minocycline. This has implications for the reparatory potential of the diseased periodontium during adjunctive treatment with minocycline.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10708666&dopt=Abstract
J Infect Dis. 1978 Mar;137(3):238-44.
The effect of chemoprophylactic use of rifampin and minocycline on rates of carriage of Neisseria meningitidis in army recruits in Finland.
Sivonen A, Renkonen OV, Weckstrom P, Koskenvuo K, Raunio V, Makela PH.
During an epidemic caused by sulfonamide-resistant group A Neisseria meningitidis (A SuR strain), rifampin (600 mg per day for four days) or minocycline (100 mg every 12 hr for five days) was administered as chemoprophylaxis to 1,540 unvaccinated recruits in the Finnish Armed Forces. Rates of carriage of all strains of N. meningitidis were initially reduced by 78% (from 60% to 13%) in the 389 men receiving rifampin and by 62% (from 70% to 26%) in the 1,151 men receiving minocycline but rose to approximately 30% in both groups four weeks after prophylaxis. The carriage of A SuR strains was similarly reduced. An individual follow-up of 636 trainees demonstrated a high rate of new infections. It is suggested that the long-term inefficiency of rifampin and minocycline is due to their inability to reduce the carriage rates enough to prevent further spread of infection after prophylaxis is descontinued. However, no new cases appeared among the men receiving the prophylaxis. Five strains highly resistant to rifampin were found after the use of rifampin (minimal inhibitory concentration, greater than or equal to 100 microgram/ml), but no minocycline-resistant strains were encountered. No unpleasant side effects were seen in subjects receiving either drug.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=416147&dopt=Abstract
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