Buy Azithromycin (Zithromax) — Online Prescription
Azithromycin — sold under the brand Zithromax and known to most patients as the "Z-Pak" — is one of the most-prescribed antibiotics in the country. Here's why a 3- or 5-day course keeps working after you stop taking it, what it actually treats, the FDA heart-rhythm warning worth knowing, and real pricing.
Medically reviewed Medically reviewed by Jill St. Germain, PharmD — NPI 1356626378 · Last updated 2026-09-06
| Active ingredient | Azithromycin |
|---|---|
| Dosage form | Tablet, oral suspension, extended-release oral suspension, IV injection |
| Administration route | Oral, intravenous |
Indications: 1 INDICATIONS AND USAGE Azithromycin is a macrolide antibacterial drug indicated for the treatment of patients with mild to moderate infections caused by susceptible strains of the designated microorganisms in the specific conditions listed below. Recommended dosages and durations of therapy in adult and pediatric patient populations vary in these indications. [see Dosage and Administration (2) ] Azithromycin is a macrolide antibacterial drug indicated for mild to moderate infections caused by d…
Contraindications: 4 CONTRAINDICATIONS • Patients with known hypersensitivity to azithromycin, erythromycin, any macrolide or ketolide drug. () • Patients with a history of cholestatic jaundice/hepatic dysfunction associated with prior use of azithromycin. () 4.1 Hypersensitivity Azithromycin tablets are contraindicated in patients with known hypersensitivity to azithromycin, erythromycin, any macrolide or ketolide drug. 4.2 Hepatic Dysfunction Azithromycin tablets are contraindicated in patients with a history of…
openFDA label data — Updated 2026-09-06Azithromycin is a prescription-only macrolide antibiotic sold under the brand Zithromax and best known as the "Z-Pak." It's FDA-approved for infections including community-acquired pneumonia, strep throat (as a penicillin-allergy alternative), ear infections, certain skin infections, and chlamydia. Its short 3- or 5-day course still delivers full treatment thanks to an unusually long tissue half-life. It is not a reliable UTI treatment and carries an FDA warning about heart-rhythm risk in patients with existing cardiac risk factors.
What azithromycin is, and how it works
Azithromycin is a macrolide antibiotic — a different drug class entirely from penicillins like amoxicillin. It works by binding to the 50S ribosomal subunit inside bacterial cells, blocking their ability to produce proteins they need to grow and multiply. That makes it bacteriostatic (it stops bacteria from multiplying, letting your immune system clear the rest) rather than directly bactericidal the way amoxicillin is.
First approved by the FDA in 1991 under the brand name Zithromax, azithromycin is now one of the most widely prescribed antibiotics in the US — largely because of a combination of broad usefulness against common infections and a dosing convenience that few other antibiotics can match.
- Community-acquired pneumonia — one of azithromycin's core FDA-approved uses.
- Pharyngitis/tonsillitis (strep throat) — typically reserved for patients with a penicillin allergy, since amoxicillin/penicillin remain first-line.
- Acute otitis media — middle ear infections.
- Skin and skin-structure infections — uncomplicated cases.
- Nongonococcal urethritis and cervicitis caused by chlamydia — historically azithromycin's signature single-dose STI treatment, though see the comparison section below for an important 2021 guideline update.
Z-Pak dosing: why a short course still works
The "why is azithromycin only given for 3 days" question is one of the most-searched things about this drug, and the real answer is pharmacokinetics, not that the infection is being treated lightly.
Most antibiotics clear from your body within hours, which is why they need dosing multiple times a day for a week or longer. Azithromycin is different: it has a tissue half-life of roughly 68 hours and concentrates heavily inside cells and tissues rather than staying in your bloodstream. The larger first-day dose rapidly builds a high tissue concentration that keeps fighting bacteria for roughly a week or more after your last pill — so a 3- or 5-day course actually delivers a much longer effective treatment window than the pack itself suggests. This is also why it's genuinely important to take every dose exactly as directed, even though the course feels short.
| Regimen | Typical dosing | Common use |
|---|---|---|
| 5-day "Z-Pak" | 500mg (two 250mg tablets) on day 1, then 250mg once daily on days 2–5 | The most recognizable azithromycin regimen — pneumonia, bronchitis, sinus infections |
| 3-day course | 500mg once daily for 3 days | Mild-to-moderate infections, some ear/sinus infections |
| Single-dose (1g or 2g) | One dose of 1000mg tablets/packets, or 2g as Zmax extended-release suspension | Historically used for chlamydia — see the comparison section below for a 2021 guideline shift |
| Pediatric oral suspension | Weight-based dosing, typically once daily for 3–5 days | Ear infections, strep throat, pneumonia in children |
Zmax is worth calling out specifically: it's a distinct, extended-release oral suspension formulation dosed as a single 2g dose — not simply a brand name for standard azithromycin, and not interchangeable, dose-for-dose, with the tablet or immediate-release suspension forms.
What azithromycin treats — and doesn't
Community-acquired pneumonia, strep throat or ear infections in patients with a penicillin allergy, certain skin infections, and chlamydia in specific clinical situations (see below). Its dosing convenience also makes it a common choice when completing a longer, multi-dose-per-day course would be a genuine adherence concern.
A routine urinary tract infection. Despite a large volume of searches asking whether it treats a UTI, azithromycin doesn't concentrate well in urine and has limited activity against E. coli, the bacteria behind roughly 80% of UTIs. Nitrofurantoin, trimethoprim/sulfamethoxazole, or fosfomycin are the standard first-line choices instead — azithromycin is only relevant when a urinary infection is actually caused by an STI organism, which your prescriber determines from testing, not symptoms alone.
Side effects, alcohol, and drug interactions
The most frequently reported side effects, from standard multi-dose clinical trial regimens:
- Diarrhea — roughly 4–5% of patients; this rate runs meaningfully higher with single high-dose regimens.
- Nausea — roughly 3%.
- Abdominal pain — roughly 2–3%.
- Headache and mild fatigue — reported less commonly; fatigue during an antibiotic course is often the underlying infection itself rather than the drug.
Antacids: Products containing aluminum or magnesium (Maalox, Mylanta, Milk of Magnesia) can reduce how much azithromycin your body absorbs if taken too close together — space them at least 2 hours apart. Calcium-based antacids and acid reducers (PPIs, H2 blockers) don't carry the same concern. Alcohol: no dangerous direct interaction the way there is with metronidazole, but it can worsen the GI side effects above and isn't doing your immune system any favors while you're fighting an infection — moderation is the sensible default for the short course.
Ibuprofen and acetaminophen (Tylenol) are both commonly taken alongside azithromycin without a significant interaction. Always give your pharmacist your complete medication list, including supplements, when starting any new antibiotic.
The FDA heart-rhythm warning
In March 2013, the FDA issued a drug safety communication after a New England Journal of Medicine study found an increased risk of cardiovascular death in patients taking a 5-day course of azithromycin compared with amoxicillin, a different antibiotic, or no antibiotic — roughly a two-fold increase in short-term risk, concentrated in the first five days of use. The mechanism is QT interval prolongation, an electrical change in the heart that can, rarely, trigger a dangerous irregular heartbeat. The risk is highest in patients who already have a prolonged QT interval, low blood potassium or magnesium, a notably slow heart rate, or who take other medications that also affect heart rhythm (certain antiarrhythmics, some other antibiotics). This isn't a reason to avoid azithromycin if you don't have those risk factors — it's a reason to make sure your prescriber and pharmacist know your full cardiac history and medication list before you start it.
Azithromycin vs. amoxicillin and vs. doxycycline
Azithromycin is frequently compared against the two other most-prescribed oral antibiotics, and each comparison answers a different real-world question:
- Azithromycin vs. amoxicillin — different drug classes (macrolide vs. penicillin) used for different infections; amoxicillin is generally first-line for strep throat and many ear/sinus infections, with azithromycin as the go-to alternative for penicillin allergy. See our full amoxicillin vs. azithromycin comparison — including where Augmentin (amoxicillin/clavulanate) fits in — for the complete breakdown.
- Azithromycin vs. doxycycline — this comparison matters most for one specific, frequently misunderstood reason: the CDC updated its national STI treatment guidelines in 2021 to make doxycycline, not azithromycin's traditional single dose, the preferred treatment for chlamydia, based on evidence it works better — especially for rectal infections. Azithromycin is now positioned mainly as the alternative for pregnancy or genuine adherence concerns. See our full azithromycin vs. doxycycline comparison for the complete picture, including Lyme disease (doxycycline's job, not azithromycin's).
Buying azithromycin: prescription, pricing, and generics
Azithromycin is prescription-only in the United States in every form. There's no legitimate over-the-counter version, in a pharmacy or online, despite that being a commonly searched question.
- Generic is the default. Brand-name Zithromax is rarely stocked today — the generic is chemically identical and, at the wholesale level, costs pennies per tablet (see the price table above). Ask your Arrow Pharmacy pharmacist for a current cash-price quote, discount card, or coupon before assuming your insurance copay is the cheapest way to save.
- A prescription doesn't require a specialist. Primary care, urgent care, dental, and telehealth providers can all prescribe azithromycin when it's appropriate for your infection.
- We can fill it fast. Because it's usually a short course, timing matters — call us at (860) 522-9289 to order or transfer a new azithromycin prescription and we'll have it ready quickly.
If cost or access is still a concern, ask us about patient assistance and discount programs — see our patient assistance programs page for options that apply broadly, not just to this drug.
No active shortage reported — Shortage records exist for this drug historically, but none are currently marked active.
FDA openFDA — Updated 2026-09-06National Average Drug Acquisition Cost (NADAC): $0.316 per tablet (AZITHROMYCIN 250 MG TABLET). This is the average price pharmacies pay wholesalers — not your out-of-pocket cost — published by CMS for pricing transparency.
CMS NADAC — Updated 2026-09-06Azithromycin (Zithromax) Prices in the USA
| Dosage | Brand-name avg. price | Generic avg. price |
|---|---|---|
| 250 mg tablet, 5-day Z-Pak (6 tablets) | $45–70 (Zithromax Z-Pak, rarely stocked) | $15–35 |
| 500 mg tablet, 3-day course (3 tablets) | $40–65 (Zithromax, rarely stocked) | $12–25 |
| 1 g (1000 mg) single-dose oral packet | $60–90 (rarely stocked) | $20–40 |
| Oral suspension, pediatric (100mg/5mL, per bottle) | $60–100 (rarely stocked) | $20–40 |
| Zmax extended-release suspension (2 g single-dose) | $220–320 | Rarely available |
Frequently asked questions
What is azithromycin used for?
The FDA has approved azithromycin for mild-to-moderate infections including community-acquired pneumonia, strep throat and tonsillitis (typically as a penicillin-allergy alternative), acute middle ear infections, certain skin and skin-structure infections, and nongonococcal urethritis and cervicitis caused by chlamydia. It's also prescribed off-label for a range of other bacterial infections based on a prescriber's clinical judgment.
Why is azithromycin given for only 3 or 5 days?
Because of how the drug behaves in your body, not because the infection is mild. Azithromycin has an unusually long tissue half-life — roughly 68 hours, versus a few hours for many antibiotics — and concentrates heavily inside cells and tissues rather than staying in the bloodstream. The front-loaded first dose builds up a high tissue concentration that continues fighting bacteria for roughly a week or more after your last pill, which is why a short course still delivers a full course of treatment. Finish every dose exactly as prescribed even though the pack is short — stopping early still risks incomplete treatment.
Is azithromycin a penicillin?
No. Azithromycin is a macrolide antibiotic, a completely different drug class from penicillin, with a different mechanism (blocking bacterial protein synthesis rather than disrupting cell walls). That's exactly why it's commonly used as the alternative for patients with a penicillin allergy who need treatment for an infection amoxicillin or penicillin would otherwise cover. If you're allergic to penicillin, azithromycin is generally considered safe on that basis alone — though tell your prescriber about any and all drug allergies regardless.
Does azithromycin treat a UTI?
Generally, no — despite being a frequently searched question, azithromycin is not a recommended treatment for a routine urinary tract infection. It doesn't concentrate well in urine and has limited activity against E. coli, the bacteria behind roughly 80% of UTIs. Current guidelines favor nitrofurantoin, trimethoprim/sulfamethoxazole, or fosfomycin instead. Azithromycin is occasionally used when a urinary infection is actually caused by an STI organism like chlamydia or mycoplasma — a distinction your prescriber makes from your specific test results, not a routine bladder-infection treatment.
Does azithromycin cause diarrhea, and what are the most common side effects?
Yes, GI side effects are the most commonly reported — diarrhea in roughly 4–5% of patients on standard multi-dose regimens, with nausea and abdominal pain each in the 2–3% range. Rates run meaningfully higher with the single high-dose regimens sometimes used for certain infections. Most GI side effects are mild and resolve after the short course ends; contact your prescriber if diarrhea is severe, watery, or persists well after finishing the medication.
Can I drink alcohol while taking azithromycin?
There's no dangerous direct interaction between alcohol and azithromycin the way there is with metronidazole. That said, alcohol can worsen the GI side effects azithromycin already tends to cause and adds strain while your body is fighting an infection, so moderation or avoiding it until you finish the short course is the more comfortable choice.
Is azithromycin safe during pregnancy?
The available evidence is reassuring — multiple observational studies covering thousands of pregnancies have not found an increased rate of major birth defects associated with azithromycin, and it's commonly used in pregnancy for specific bacterial infections, including some STIs. That said, which antibiotic is appropriate can depend on your trimester and specific diagnosis, so this is always a decision to make with your prescriber rather than a blanket yes.
How long does azithromycin stay in your system, and how long until it starts working?
Because of its long tissue half-life, azithromycin can remain detectable in your system for up to 1–2 weeks after finishing a course, even though you only take it for 3–5 days. Many people notice symptom improvement within 2–3 days of starting treatment, though this varies by infection and severity — always complete the entire prescribed course even once you feel better, since the drug is still actively working in your tissues after your last dose.
Can I take azithromycin with ibuprofen, Tylenol, or other medications?
Ibuprofen and acetaminophen (Tylenol) don't have a significant interaction with azithromycin and are commonly used together for pain or fever during treatment. The interactions that matter more: antacids containing aluminum or magnesium (like Maalox, Mylanta, or Milk of Magnesia) can reduce azithromycin absorption if taken too close together — space them at least 2 hours apart — and azithromycin can interact with certain heart-rhythm medications and other drugs that prolong the QT interval (see the warning below). Always give your pharmacist your complete medication list when starting a new antibiotic.
Does azithromycin need to be refrigerated?
No — this is a common point of confusion. Unlike some antibiotic suspensions, reconstituted azithromycin oral suspension does not require refrigeration and is stable at normal room temperature (up to about 86°F); refrigerating it is optional, not necessary. Keep it tightly closed, protect it from freezing, and discard any unused suspension after 10 days per the FDA label.
Can I buy azithromycin over the counter or without a prescription?
No. Azithromycin is prescription-only in the United States in every form — there is no legitimate over-the-counter version, despite that being a commonly searched question. A website offering it with "no prescription needed" is a red flag for an unlicensed or rogue online pharmacy rather than a legitimate shortcut.
Can azithromycin be given to dogs or cats?
Veterinarians do sometimes prescribe azithromycin for pets, but veterinary dosing, formulation, and monitoring are different from human prescribing — never give a pet a human azithromycin prescription (or the reverse) without a veterinarian's specific direction. This page covers azithromycin as it's prescribed for people.
Sources
- Zithromax (azithromycin) — FDA-approved prescribing information (label) — U.S. Food and Drug Administration
- NADAC (National Average Drug Acquisition Cost) — AZITHROMYCIN 250 MG TABLET — CMS
- openFDA Drug Shortages — U.S. FDA
- FDA Drug Safety Communication: Azithromycin (Zithromax or Zmax) and the risk of potentially fatal heart rhythms — U.S. Food and Drug Administration
- Chlamydial Infections — STI Treatment Guidelines, 2021 — CDC
- Azithromycin price data (average retail cash price) — GoodRx (consumer price reference)