azithromycin

General

Pronunciation:
aye-zith-roe-mye-sin

Trade Name(s)

• Zithromax
• Zmax

Ther. Class.
agents for atypical mycobacterium
anti-infectives

Pharm. Class.
macrolides

Indications

• Treatment of the following infections due to susceptible organisms:
  • Upper respiratory tract infections, including streptococcal pharyngitis, acute bacterial exacerbations of chronic bronchitis and tonsillitis,
  • Lower respiratory tract infections, including bronchitis and pneumonia,
  • Acute otitis media,
  • Skin and skin structure infections,
  • Nongonococcal urethritis, cervicitis, gonorrhea, and chancroid.
• Prevention of disseminated Mycobacterium avium complex (MAC) infection in patients with advanced HIV infection.

Unlabeled Use(s):

• Prevention of bacterial endocarditis.
• Treatment of cystic fibrosis lung disease.
• Treatment and post-exposure prophylaxis of pertussis in infants.

Action

Inhibits protein synthesis at the level of the 50S bacterial ribosome.

Therapeutic Effect(s):

Bacteriostatic action against susceptible bacteria.

• Active against the following gram-positive aerobic bacteria:
  • Staphylococcus aureus,
  • Streptococcus pneumoniae,
  • S. pyogenes (group A strep).
• Active against these gram-negative aerobic bacteria:
  • Haemophilus influenzae,
  • Moraxella catarrhalis,
  • Neisseria gonorrhoeae.
• Also active against:
  • Bordetella pertussis
  • Mycoplasma,
  • Legionella,
  • Chlamydia pneumoniae,
  • Ureaplasma urealyticum,
  • Borrelia burgdorferi,
  • M. avium.
• Not active against methicillin-resistant S. aureus.

Pharmacokinetics

Absorption: Rapidly absorbed (40%) after oral administration. IV administration results in complete bioavailability.

Distribution: Widely distributed to body tissues and fluids. Intracellular and tissue levels exceed those in serum; low CSF levels.

Protein Binding: 7–51%.

Metabolism and Excretion: Mostly excreted unchanged in bile; 4.5% excreted unchanged in urine.

Half-life: 11–14 hr after single dose; 2–4 days after several doses.

TIME/ACTION PROFILE (serum)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity to azithromycin, erythromycin, or other macrolide anti-infectives;
• History of cholestatic jaundice or hepatic dysfunction with prior use of azithromycin;
• QT interval prolongation, hypokalemia, hypomagnesemia, or bradycardia;
• Concurrent use of quinidine, procainamide, dofetilide, amiodarone, or sotalol.

Use Cautiously in:

• Severe hepatic impairment (dose adjustment may be required);
• Severe renal impairment (CCr <10 mL/min);
• Myasthenia gravis (may worsen symptoms);
• Geri:  May have ↑ risk of QT interval prolongation;
• OB:   Use only if potential maternal benefit justifies potential fetal risk;
• Lactation: Use during breast feeding only if potential maternal benefit justifies potential risk to infant;
• Pedi:  Neonates (↑ risk of infantile hypertrophic pyloric stenosis at up to 42 days of life).

Adverse Reactions/Side Effects

CNS: dizziness, seizures, drowsiness, fatigue, headache

CV: TORSADES DE POINTES, chest pain, hypotension, palpitations, QT interval prolongation

Derm: ACUTE GENERALIZED EXANTHEMATOUS PUSTULOSIS, DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS), STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, photosensitivity, rash

EENT: ototoxicity

F and E: hyperkalemia

GI: HEPATOTOXICITY, CLOSTRIDIOIDES DIFFICILE-ASSOCIATED DIARRHEA (CDAD), abdominal pain, diarrhea, nausea, cholestatic jaundice, ↑ liver enzymes, dyspepsia, flatulence, melena, oral candidiasis, pyloric stenosis

GU: nephritis, vaginitis

Hemat: anemia, leukopenia, thrombocytopenia

Misc: HYPERSENSITIVITY REACTIONS (INCLUDING ANAPHYLAXIS AND ANGIOEDEMA)

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

• Quinidine, procainamide, dofetilide, sotalol, and  amiodarone  may ↑ risk of QT interval prolongation; concurrent use should be avoided.
•  Aluminum-  and  magnesium-containing antacids  ↓ peak levels.
•  Nelfinavir  ↑ levels (monitor carefully); azithromycin also ↓ nelfinavir levels.
•  Efavirenz  ↑ levels.
• May ↑ the effects and risk of toxicity of  warfarin  and  zidovudine.
• Other macrolide anti-infectives have been known to ↑ levels and effects of digoxin, theophylline, ergotamine, dihydroergotamine, triazolam, carbamazepine, cyclosporine, tacrolimus, and  phenytoin ; careful monitoring of concurrent use is recommended.

Route/Dosage

Most Respiratory and Skin Infections

PO (Adults): 500 mg on 1st day, then 250 mg/day for 4 more days (total dose of 1.5 g);  Acute bacterial sinusitis– 500 mg once daily for 3 days.

PO (Children  ≥ 6 mo):  Pneumonia/Pertussis– 10 mg/kg (not to exceed 500 mg/dose) on 1st day, then 5 mg/kg once daily (not to exceed 250 mg/dose) for 4 more days.  Pharyngitis/tonsilitis– 12 mg/kg once daily for 5 days (not to exceed 500 mg/dose);  Acute bacterial sinusitis– 10 mg/kg once daily for 3 days.

PO Neonates:  Pertussis, treatment and post-exposure prophylaxis– 10 mg/kg once daily for 5 days.

Otitis Media

PO (Children  ≥6 mo): 30 mg/kg single dose (not to exceed 1500 mg/dose)   or  10 mg/kg once daily (not to exceed 500 mg/dose) for 3 days   or  10 mg/kg (not to exceed 500 mg/dose) on 1st day, then 5 mg/kg once daily (not to exceed 250 mg/dose) for 4 more days.

Acute Bacterial Exacerbations of Chronic Bronchitis

PO (Adults): 500 mg on 1st day, then 250 mg once daily for 4 more days (total dose of 1.5 g)   or 500 mg once daily for 3 days.

Community-Acquired Pneumonia

IV PO (Adults):  More severe– 500 mg IV every 24 hr for at least 2 doses, then 500 mg PO every 24 hr for a total of 7–10 days;  Less severe– 500 mg PO, then 250 mg/day PO for 4 more days.

PO (Children  >6 mo): 10 mg/kg on 1st day, then 5 mg/kg once daily for 4 more days.

Pelvic Inflammatory Disease

IV PO (Adults): 500 mg IV every 24 hr for 1–2 days, then 250 mg PO every 24 hr for a total of 7 days.

Endocarditis Prophylaxis

PO (Adults): 500 mg 1 hr before procedure.

PO Children: 15 mg/kg 1 hr before procedure.

Nongonococcal Urethritis, Cervicitis, Chancroid, Chlamydia

PO (Adults): Single 1-g dose.

PO Children:  Chancroid:  Single 20-mg/kg dose (not to exceed 1000 mg/dose).  Urethritis or cervicitis:  Single 10-mg/kg dose (not >1000 mg/dose).

Gonorrhea

PO (Adults): Single 2-g dose.

Prevention of Disseminated MAC Infection

PO (Adults): 1.2 g once weekly (alone or with rifabutin).

PO Children: 5 mg/kg once daily (not >250 mg/dose) or 20 mg/kg (not >1200 mg/dose) once weekly (alone or with rifabutin).

Cystic Fibrosis

PO (Children  ≥6 yrs, ≥40 kg): 500 mg every Monday, Wednesday, and Friday.

PO (Children  ≥6 yrs, 25 kg to <40 kg): 250 mg every Monday, Wednesday, and Friday.

Availability (generic available)

Powder for injection (requires reconstitution and dilution): 500 mg/vial

Powder for oral suspension (cherry and banana flavor) (requires reconstitution): 1 g/pkt

Cost:

Generic: $72.45/3 pkts

Powder for oral suspension (cherry, creme de vanilla, and banana flavor) (requires reconstitution): 100 mg/5 mL, 200 mg/5 mL

Cost:

Generic: 100 mg/5 mL $34.88/15 mL, 200 mg/5 mL $34.88/22.5 mL

Tablets: 250 mg, 500 mg, 600 mg

Cost:

Generic: 250 mg $8.82/6, 500 mg $10.03/3, 600 mg $104.62/30

Assessment

• Assess patient for infection (vital signs; appearance of wound, sputum, urine, and stool; WBC) at beginning of and throughout therapy.
• Obtain specimens for culture and sensitivity before initiating therapy. First dose may be given before receiving results.
• Observe for signs and symptoms of anaphylaxis (rash, pruritus, laryngeal edema, wheezing). Notify health care professional immediately if these occur.
• Assess patient for skin rash frequently during therapy. Discontinue azithromycin at first sign of rash; may be life-threatening. Stevens-Johnson syndrome or toxic epidermal necrolysis may develop. Treat symptomatically; may recur once treatment is stopped.

Lab Test Considerations:

May cause ↑ serum bilirubin, AST, ALT, LDH, and alkaline phosphatase concentrations.

• May cause ↑ creatine phosphokinase, potassium, prothrombin time, BUN, serum creatinine, and blood glucose concentrations.
• May occasionally cause ↓ WBC and platelet count.

Potential Diagnoses

• Risk for infection (Indications)  (Side Effects) 
• Noncompliance (Patient/Family/Teaching) 

Implementation

• PO Administer 1 hr before or 2 hr after meals.
  • For administration of single 1-g packet, thoroughly mix entire contents of packet with 2 oz (60 mL) of water. Drink entire contents immediately; add an additional 2 oz of water, mix and drink to assure complete consumption of dose. Do not use the single packet to administer doses other than 1000 mg of azithromycin. Pedi:  1-g packet is not for pediatric use.

Patient/Family Teaching

• Instruct patients to take medication as directed and to finish the drug completely, even if they are feeling better. Take missed doses as soon as possible unless almost time for next dose; do not double doses. Advise patients that sharing of this medication may be dangerous.
• Instruct patient not to take azithromycin with food or antacids.
• May cause drowsiness and dizziness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
• Advise patient to use sunscreen and protective clothing to prevent photosensitivity reactions.
• Advise patient to report symptoms of chest pain, palpitations, yellowing of skin or eyes, or signs of superinfection (black, furry overgrowth on the tongue; vaginal itching or discharge; loose or foul-smelling stools) or rash.
• Instruct patient to notify health care professional if fever and diarrhea develop, especially if stool contains blood, pus, or mucus. Advise patient not to treat diarrhea without advice of health care professional.
• Advise patients being treated for nongonococcal urethritis or cervicitis that sexual partners should also be treated.
• Instruct parents, caregivers, or patient to notify health care professional if symptoms do not improve.
• Rep:  Advise female patient of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breast feeding. Advise women to monitor breast-fed infant for diarrhea, vomiting, or rash.

Evaluation/Desired Outcomes

Resolution of the signs and symptoms of infection. Length of time for complete resolution depends on the organism and site of infection.