- 1 Zithromax (Z-Pak) is an antibiotic that treats a number of infections. The drug is linked to an increased risk of fatal heart problems.
- 2 Zithromax and Z-Pak Dosage
- 3 How Zithromax Works
- 4 Side Effects of Zithromax
- 5 Zithromax and Antibiotic Overuse
- 6 Zithromax Lawsuits
Zithromax has been highly profitable for its manufacturer, Pfizer. Although the wide availability of generics means that Zithromax no longer brings in the billions per year it once did, U.S. sales still totaled $435 million in 2012.
In March 2013, however, the FDA warned the public about fatal heart-related risks of Zithromax that may open Pfizer up to legal liability.
Zithromax and Z-Pak Dosage
Zithromax is most familiar to the public as the “Z-Pak,” a convenient five-day pill regimen with half the doses of many other popular antibiotics. As an antibiotic, it is not effective in treating viral infections such as a cold or the flu. A doctor determines whether an infection or disease is bacterial by examining the symptoms—respiratory infections, for example, are often bacterial rather than viral.
With the Z-Pak, patients take a double dose on the first day and then a normal dose for four days. In some cases, Zithromax is prescribed in a single, large dose. This “megadose” can be used to treat ear infections in children or sexually transmitted diseases, such as gonorrhea. A three-day treatment option for sinusitis and some other bacterial infections is also available, but is less common than the Z-Pak.
Doctors choose an antibiotic based on its effectiveness against specific strains of bacteria, its strength against bacterial resistance, and its ease of use. For example, patients are more likely to correctly follow the treatment regimen of a more convenient antibiotic such as Zithromax.
How Zithromax Works
Zithromax belongs to a class of antibiotics called macrolides, which are bacteriostatic – meaning they treat infections by preventing bacteria from multiplying and producing the proteins that are essential for their growth. Eventually, the remaining bacteria die or are killed by the immune system, not by the drug itself. This is in contrast to bactericidal antibiotics, which kill bacteria.
Zithromax does not break down in the body as quickly as other antibiotics. Instead of floating feely in the blood, it gets picked up by white blood cells that fight bacteria. The white blood cells take the medicine to the front lines of their struggle with germs, where it becomes concentrated in the tissues surrounding the infection. That concentration helps it remain in the body longer, which means patients need fewer doses to beat their infections.
In clinical trials, Zithromax was effective at fighting bacterial infection, including some antibiotic-resistant strains. Studies conducted before approval of the drug measured its minimum inhibitory concentration (MIC) in relation to a host of bacteria. A MIC is the lowest concentration of an antibiotic that will inhibit the growth of bacteria and thereby kill them. A lower MIC means a more effective antibiotic.
In a 1991 study in the European Journal of Clinical Microbiology and Infectious Diseases, Zithromax was found to have a markedly low MIC compared with three other types of antibiotics, meaning it was highly effective—resolving, for example, 92 percent of gonorrhea infections treated.
Side Effects of Zithromax
In most cases, Z-Paks are well-tolerated in patients. In clinical trials, side effects were found to occur in approximately 12 percent of patients, and less than 10 percent of those side effects were classified as severe. Most side effects were mild and included diarrhea, nausea and abdominal pain. No other side effects that occurred in clinical trials had a frequency greater than 1 percent.
|Side effects with a frequency of less than 1 percent include:|
|Palpitations and chest pain||Vomiting|
|Jaundice (yellowing of skin)||Inflammation|
|Dizziness, headache and vertigo||Fatigue|
|Non-fatal allergic reactions|
Some rare but serious side effects have been reported, however, including fatal heart problems, allergic reactions and liver disease.
Abnormal Heart Activity and Sudden Cardiac Death
In May 2012, a study in the New England Journal of Medicine reported an increase in cardiovascular death in patients treated with azithromycin compared with patients treated with amoxicillin, ciprofloxacin or no drug. The study was prompted by evidence found in FDA adverse events databases that azithromycin promotes irregular heartbeats, which caused the study’s authors to hypothesize that incidences of cardiovascular death may increase for patients on the drug. Researchers concluded that patients at a high risk for cardiovascular death, including those with existing QT interval prolongation, low blood levels of potassium or magnesium, a slower than normal heart rate or patients taking drugs to treat arrhythmias, were more likely to die while taking azithromycin than patients on other antibiotics or none at all.
The risk of death while on azithromycin increased proportionally with the patients’ Cardiovascular Risk Score: The study found 245 excess deaths in patients with the highest risk scores, compared with just 9 excess deaths in patients with the lowest risk scores. Since this increased death rate did not continue once patients finished their 5-day courses of azithromycin, researchers concluded the increased risk must stem from the drug and only last as long as the drug remains in the body.
Following this study, the FDA issued a public statement detailing the study and warning that the Z-Pak may have previously unknown side effects relating to risk of cardiovascular death. In March 2013, based on new studies funded by Pfizer in response to the research in the New England Journal of Medicine, the FDA issued a stronger public warning that azithromycin, including brand names Zithromax, Zmax, Azithrocin and Azin, “can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm.”
People with diabetes, a high risk of heart failure, or a previous heart attack are at the most risk of abnormal heart rhythms while taking Zithromax. The authors of the New England Journal study say doctors should consider prescribing a different drug, such as amoxicillin, for such high-risk patients. For the vast majority of patients who have no heart problems, there is no increased risk. The original NEJM study found only 47 additional deaths per 1 million courses of treatment, most of which occurred in patients with serious pre-existing heart conditions.
A recent study sponsored by the Danish Medical Research Council found no evidence of increased risk of death for young and middle-aged adults without heart problems who took Zithromax compared with those who took a different antibiotic such as penicillin. Researchers concluded that “any increased risk of cardiovascular death associated with azithromycin is restricted to high-risk patients” with a history of heart disease or problems.
Hepatotoxicity (Toxic Liver Disease)
Because Zithromax is metabolized and processed in the liver, patients with liver problems or abnormal liver function may be at risk of serious problems from the drug. Hepatotoxicity (toxic liver disease) and hepatitis have been reported in patients taking Zithromax, occasionally resulting in death. Zithromax should be discontinued if there are signs of hepatitis, such as fatigue, muscle aches, loss of appetite, dark urine or abdominal discomfort.
Serious allergic reactions to Zithromax have been reported, including angioedema (rapid swelling), anaphylaxis (allergic shock), and skin reactions. In rare cases, these reactions resulted in death.
If an allergic reaction occurs while on Zithromax, contact a doctor immediately.
Zithromax and Antibiotic Overuse
One of the most important issues with Zithromax is one that plagues almost all antibiotics: overprescription. Many patients get prescriptions for antibiotics when they do not need them: More than 133 million courses of antibiotics are prescribed by doctors each year, according to the American College of Physicians, and about half of those are prescribed for viral infections that antibiotics cannot treat. This overuse results in the evolution of antibiotic-resistant “super germs,” as bacteria that survive the antibiotic’s onslaught pass on their strengths during reproduction.
These drug-resistant bacteria can cause very serious illnesses. In 2011, for example, a multidrug-resistant bacterial “superbug” killed 12 people after striking a health care center run by the National Institutes of Health. Such antibiotic-resistant super germs will only get more common if overuse of antibiotics continues.
Patients with the flu, a cold or any other kind of viral infection should not ask doctors to prescribe an antibiotic. Not only will it not help, since antibiotics have no effect on viruses, but taking such medication can reduce future responsiveness to antibiotics. Some bacterial infections do not need antibiotics, either. Doctors decide when an antibiotic is needed.
In March 2013, Pfizer noted that in collaboration with the FDA, it had “updated the Zithromax (azithromycin) label with regards to a specific, rare heart rhythm abnormality in patients with risk factors” for heart disease and that “this potential risk is well established in macrolide antibiotics.” This was the first public information supplied by Pfizer about cardiovascular death associated with Zithromax in the two decades since its introduction.
Because Pfizer did not issue any warnings to the public about the danger of cardiovascular death until nearly 22 years after it started marketing the drug, families of those who have died while taking Zithromax may be able to sue the drugmaker. Drug manufacturers are expected to thoroughly test their products and ensure their safety before releasing them to the market. Any lawsuit filed against Pfizer over Zithromax will likely allege that the drugmaker either knew or should have known about the increased risk of cardiovascular death, and failed in its duty to warn the public.