Macrolide antibiotics include

Azithromycibn. clarithromycin, dirithromycin, erythromycin and troleandomycin

Interacting drugs- summary

Azithromycin +

Antacids decr aluminium and magnesium -containing antacids reduce the peak serum levels but not extent of azithromycin absorption

Tacrolimus - azithromycin increase the plasma levels of tacrolimus increasing the risk of toxicity

Theophylline azithromycin did not affect the plasma levels or pharmacikinetics of theophylline administered as a single IV dose. The effect of azithromycin on multiple doses is not known. however concurent use of macrolides and theophylline has been ssociated with increase in serum concentrations of theophylline. Therefore carefully monitor theophylline levels in patients receiving azithromycin and theophylline concurrently.

Warfarin azithromycin did not affect the prothrombin time (PT) response to a single dose of warfarin. However concurent use of macrolides and warfarin has been associated with increased anticoagulant effects. Carefully monitor PT in all patients treated with azithromycin and warfarin concomittantly

Drug/Food interactions

Food decreases absorption of azithromycin capsules, reducing maximum concentrations by 52% and bioavailability by 43%. When azithromycin suspension was administered with food to 28% healthy adult males, the rate of absorption (Cmax) increased by 58% while the extent of absorption (AUC) was unchanged .

Take 1 hour before or 2 hours after a meal. Do not take with food

Rare serious allergic reactions including angioedema and anaphylaxis,have been reported with azithromycin therapy Most side effects are mild to moderate in severity and are reversible upon discontinuatiuon of the drug. Mild to moderate nausea,vomiting, abdominal pain, diarrhoea. Angioedema. Cholestatic hepatitis(rare).

Cardiovascular- Chest pain

GI- dyspepsia, constipation,anorexia,flatulance, gastritis

CNS-headache, hyperkinesia, dizziness, agitation, nervousness, insomnia. Hypersensitivity- rash

Special senses- conjuntivitis

Lab test abnormalities- elevated serum creatine phosphatase, potassium ALT, GGT, and AST, leukopenia, neutropenia, decreased platelet counts and elevated serum alkaline phosphatase, bilirubin, BUN< creatinine, blood glucose

Hypersens to the drug or other macrolides.

Special precautions:

Impaired liver & renal function.pregnancy & lactation. Children.

Superinfection- Use of antibiotics (especially for prolonged or repeate therapy) may result in bacterial or fungal overgrowth of nonsusceptible organisams. Such overgrowth may lead to secondary infection.

Photosentization- may occur, therfore patients advised to take protective measures against exposure to sunlight or ultraviolet light.

Warnings

Pneumonia- azithromycin is only safe and effective in the treatment of community acquired pneumonia of mild severity due to S pneumoniae and H influenzae in patients appropiate for out patient oral therapy. Do not use in patients with pneumonia who are judged to be inappropiate for out patient oral therapy because of moderate to severe illness or known risk factors.

Gonorrhea or syphilis- azithromycin at the recomended dose should not be be relied upon to treat gonorhea or syphilis. Antimicrobial agents used in high doses for short time to treat non-gonococccal urethritis may mask or delay the symptoms of incubating gonorrhea or syphilis.

Pseudomembranous colitis- has been reported with nearly all bacterial agents and may range in severity to mild life threatening. Therefore it is important to consider this diagnosis in patients who present with diarrhea and subseqent to the adminisatration of antibacterial agents.

Cardiac effects- Ventricular arrhythmias including ventricular tachycardia and torsade de pointes , in individuals with prolonged QT intervals have not been reported in clinical trials with azithromycin.

Hypersensitivity reactions- Rare serious allergic reactions including angioedema and anaphylaxis have been reported on azithromycin therapy. When symptomatic therapy was discontinued the allergic symptoms recurred soon thereafter in some patients without further further azithromycin exposure.

Renal/hepatic function impairment- because azithromycin is prinicipally eliminated via the liver, excercise caution when azithromycin is administered to patients with impaired hepatic function.

Elderly- dosage adjustment does not appear to be necessary for older patients with normal renal and hepatic function receiving treatment with this dosage regimen Pregnancy- use during pregnancy only ifclearly needed.

Lactation- Excercise caution when administering to a nursing woman.

Children- safety and efectiveness in children < 6 months of age have not been established

Azithromycin was approved by the FDA in November 1991

Skin and soft tissue infection Respiratory tract infection

Dosage: Adiminister at least 1 hour before or 2 hours after a meal. Mild to moderate infections- more than 16 years- 500mg as a single dose on the first day followed by 250mg once daily on 2 through 5 for a total dose of 1.5g.

Missed dose-

1. If you miss a dose of this medicine, take it as soon as possible.

2. However, if it is almost time for next dose, skip the missed dose and go back to your regular dosing schedule.

3. Do not double doses.

1.Caution patients to take azithromycin at least 1 hour before or 2 hours after a meal. Azithromycin should not be mixed or taken with food.

2. Caution patients not to take aluminium and magnesium containing antacids and azithromycin simutaneously.

3. Patients should discontinue azithromycin immediately and contact a physician if any signs of an allergic reaction occur.

Pharmacology:

Azithromycin is an azalide antibiotic, a subclass of macrolides. Azithromycin is derived from erythromycin; however it differs chemically from eryhtromycin in that a methyl-substituted nitrogen atom is incorporated in the lacone ring. Azithromycin acts by binding to the 50 S ribosomal subunit of susceptible organisms and thus interfering with the microbial protein synthesis. Nulceic acid synthesis is not affected.

Pharmacokinetics:

Rapidly absorbed and widely distributed throughout the body. Biliary excretion of azithromycin, predominantly as unchanged drug is a major route of elimination

Food decreases absorption of azithromycin capsules, reducing maximum concentrations and bioavailability Take 1 hour before or 2 hours after a meal. Do not take with food

Pregnancy:

There are no adequate and well controlled studies in pregnant women. Use during pregnancy only if clearly needed.

Lactation:

Not known whether azithromycin is excreted in breast milk. Excercise caution while administering to a nursing woman

Children- Safety and effectiveness in children < 6 months of age have not been established