Tadalafil entfaltet seine Wirkung über eine selektive Hemmung der PDE5, wodurch die Konzentration von cGMP im glatten Muskelgewebe stabil bleibt. Diese biochemische Modulation resultiert in einer langanhaltenden Relaxation der Gefäßwände. Der Wirkstoff wird nach oraler Einnahme effizient resorbiert, mit einer Bioverfügbarkeit von rund 80 %. Seine Halbwertszeit von bis zu 36 Stunden ist innerhalb dieser Substanzklasse außergewöhnlich. Abgebaut wird er in der Leber, hauptsächlich durch CYP3A4, mit anschließender biliärer Exkretion. Typische unerwünschte Wirkungen entstehen durch eine verstärkte Vasodilatation, etwa Kopfschmerzen oder Flush. Pharmakologisch wird cialis generika vor allem durch die verlängerte Wirkungsdauer charakterisiert.

Antimicrobials

Peptide Antibiotics
– Inhibit or compromise PGN or Outer Membrane (O.M.) – Bactericidal – Narrow Spectrum : Gram-positives or Gram –negatives – NOT absorbed from GIT (Gastrointestinal tract) – Resistance “generally” rare • Topical generally • Systemic toxicity – nephrotoxic, neurotoxic, ototoxic • Otitis externa, keratitis, dermatitis (ears, eyes, skin)
• “Last-resort” antibiotic - Vancomycin (humans primarily)
Peptide Antibiotics
• Bacitracin : inhibits peptidoglycan synthesis – Bacillus subtilis
– Topical (skin, eye, ear)
• Triple-Abx : with Polymyxin B and Neomycin – Bacitracin replaces Penicillins as topical (Staph) • Allergic contact sensitivity with Penicillins Peptide Antibiotics
• Polymyxins (Types A through E) – Damage Outer Membrane – Bacillus polymyxa
– Polymyxin B and E (called Colistin) – Gram –ves including PSA

• Topical (otitis, keratitis, dermatitis) : recall Surolan®
• Dogs/cats
• Horses - intra-uterine for Pseudomonas/Klebsiella

• Binds LPS - Endotoxin A
– Reduces LPS-reduced pyrexia at sub-MIC levels Peptide Antibiotics
• Glycopeptides: Gram-positives only – Inhibit PGN – Vancomycin largely reserved as “last-resort” drug in humans
• MRSA, Multi-drug resistant (MDR) Clostridium difficile or – E.U. ban on Avoparcin growth promoter in feed 1996 • VRE’s frequency in poultry dropped immediately • Not swine ? • Reason – Co-selection of Vancomycin/Macrolide resistance • Tylosin (Macrolide) was being used as growth promoter in feed • VRE in N.A. - arisen from hospitals Antimicrobial Drugs
• Inhibitors of Protein Synthesis
– Aminoglycosides/Aminocyclitols (ie. Streptomycin, Spectinomycin) – Lincosamides (i.e Lincomycin) – Chloramphenicol and Florfenicol Tetracyclines: Bacteriostatic
– Chlortetracycline (1944) – Oxytetracycline, Tetracycline – Semisynthetics – G+ve, G-ve, anaerobes – FIPs (Brucella, Listeria) – Obligate intracellular (Chlamydophila, – Efflux pumps – PSA, Proteus mirabilis, most – Enterobacteriaceae (E. coli, Salmonella, Klebsiella, Enterobacter) and Clostridia Tetracyclines
• Dogs/Cats - Tet, Oxytet, Doxycyline, Minocycline • Horses/Ruminants/ Swine - Oxytetracycline – Potomac Horse Fever (Neorickettsia), Leptospirosis
– Parenteral (I.V., I.M), oral (p.o.) in dogs, cats and “monogastric” food – Water/food admin – TeracyclineJ (water soluble tetracyline powder) – TerramycinJ (oxytetracycline in feed) Tetracyclines
• Dysbiosis in GIT (biliary excretion, passive diffusion into large – Predispose to enterocolitis (Salmonella, Candida, Clostridium spp. ) – Equine risk, other hindgut fermenters (Guinea pigs in particular) • Not recommended for young animals (bone, teeth) • Cardiac effects – Ca+2 binding during rapid I.V. admin Aminoglycosides(AMGs): Bactericidal
– Streptomycin/Dihydrostreptomycin
– Neomycin
– Kanamycin, Amikacin, Apramycin,
Tobramycin; Gentamicin
– Spectinomycin

Aminoglycosides: Bactericidal
• Potency/Spectrum/resistance to resistance mechanism(s) – Tobramycin>Amikacin/Gentamicin>Neomycin/Kanamycin>Streptomycin – No GIT uptake • Streptomycin/Dihydrostreptomycin: Dog, Cattle, poultry (i.m.) – Leptospirosis (with a Penicillin – this is off-label in N.A.) – Resistance has reduced use – Triple-Mix Antibiotics (skin, eye) with : Bacitracin and Polymyxin B – Otitis externa (Tresaderm®) – Oral route as well • dog/cat • Calves: oral colibacillosis – most nephrotoxic Aminoglycosides: Bactericidal
• Kanamycin (parent compound) used little due to widespread resistance • Amikacin, Gentamicin or Tobramycin are excellent options for PSA – Amikacin: Dog/Cat/Horse/Cattle (route – parenteral) – Tobramycin: ’d PSA activity (combine with ticarcillin) – Apramycin: licensed for swine (Canada, not U.S.) • enteritis (E. coli) p.o
Aminoglycosides: Bactericidal
– Gentamicin: Dog/Cat/Horse/Cattle/chicks/piglets (parenteral) or water
• Gentocin® : dog, cat, piglet (i.m.), horse ,dog, cow (intrauterine), chick (s.q.)
• 1 day old chicks, 3 day old piglets (long withdrawal time - kidney
residues)
• Gram negative sepsis (including foals, ferrets, rabbits, rodents) – I.V.
• Opthalmic spray for pinkeye (US), bacterial dermatitis in dogs (Canada)
• Spectinomycin: Narrow spectrum, little nephro- or ototoxicity but – Mycoplasma’s (poultry), colibacil osis (swine) and swine dysentery (Brachyspira) and porcine proliferative enteropathy (Lawsonia) in combination with Lincomycin (Lincosamide)

Source: http://people.upei.ca/bdespres/Antimicrobials-II-10.pdf