Pharmachology Assignment

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AZITHROMYCINE

Generic name: Azithromycin

Trade (Brand) names: Zithromax
• Canadian trade name: Apo-Azithromycin

Available forms:
• Injection: 500 mg
• Powder for oral suspension: 100mg/5 ml, 200mg/5ml; 1,000 mg/Packet • Tablets: 250 mg, 500 mg, 600 mg

Drug classification:
• Pharmacoterapeutic: Macrolide
• Clinical: Antibiotic

Action:
Azithromycin prevents bacteria from growing by interfering with their protein synthesis. Azithromycin binds to the 50S subunit of the bacterial ribosome, and thus inhibits translation of mRNA. Nucleic acid synthesis is not affected. Pharmacokinetics:

Unlike erythromycin, azithromycin is acid-stable and can therefore be taken orally with no need of protection from gastric acids. It is readily absorbed; its absorption is greater on an empty stomach. Time to peak concentration in adults is 2.1 to 3.2 hours for oral dosage forms and 1 to 2 hours for intravenous (IV) forms. Due to the high concentration in phagocytes, azithromycin is actively transported to the site of infection. During active phagocytosis, large concentrations of azithromycin are released. The concentration of azithromycin in the tissues can be over 50 times higher than in plasma. This is due to ion trapping and the high lipid solubility. Azithromycin's half-life allows a large single dose to be administered and yet maintain bacteriostatic levels in the infected tissue for several days. The new "Zmax" formulation of azithromycin is an enteric-coated suspension that releases the drug in a single 2g dose once it has cleared the stomach, reducing the GI side-effects of high-dose Azithromycin. Half-Life: 6-8hr

Onset of action: Variable
Peak: 2.1 to 3.2 hr for oral dosages and 1to 2 hr for IV
Duration: Up to 24 hr
METABOLISM:
Following a single 500 mg dose, plasma concentrations of azithromycin declined in a polyphasic pattern with a mean apparent plasma clearance of 630 mL/min and a terminal elimination half-life of 68 hours. The prolonged terminal half-life is thought to be due to extensive uptake and subsequent release of drug from tissues. Biliary excretion of azithromycin, predominantly unchanged, is a major route of elimination. Over the course of a week, approximately 6% of the administered dose appears as unchanged drug in urine. CATIONS:

Mild to moderate infections of upper and lower respiratory (Tonsillitis Pharyngitis) –urethral, endocervical, or rectal infections, Skin infections, otitis media, HIV infection and PID (pelvic inflammatory disease).

ROUTE:
PO - IV

Dosage/Frequency:
• Po:
Adults, elderly: 500 mg single dose on the first day

250 mg daily (on days 2-5)

Children: 10-20mg/kg/day in divided doses up to

20-30mg/kg/day for severe infection. • IV:

Adults, elderly: 500 mg single daily dose (during: 2 days)

Interaction:

Drug-drug:

May increase metabolism of carbamazepine, cyclosporine and phenytoin. May increase effects of digoxin.With theophylline may increase risk of theophylline toxicity. Also increase effect of warfarin.

Drug-food:

Any food may decrease absorption of multidose oral suspension for mulation.Advise patient to take drug on empty stomach.

Drug-lifestyle:

Sun exposure may cause photosensitivity reaction. Advise patient to avoid excessive sunlight exposure.

Contraindications:

Major contraindication is hypersensitivity. Azithromycin is contraindicated in patients who are allergic to it. Caution should be used in any patient hepatic insufficiency because the ability to breakdown Azithromycin for excretion may be compromised. Caution should be exercised during pregnancy, biliary function, GI disease, and cardiac arrhythmias. Azithromycin should not be administered in...
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