Piperacillin with tazobactam (Tazocin, Zosyn): a hospital antibiotic explained

Piperacillin with tazobactam is a combination antibiotic. Piperacillin belongs to the penicillin family, which the NHS lists as one of the main groups of antibiotics. Many bacteria defend themselves by producing enzymes that break penicillins down, and tazobactam blocks some of those enzymes. The manufacturer leaflet explains that, together, the two medicines kill more kinds of bacteria than piperacillin does on its own.

It is sold under several brand names and also as unbranded generic products. In the UK it is most often seen on hospital drug charts as piperacillin-tazobactam, or by the brand name Tazocin; Zosyn is the name used in the United States. The active ingredients are the same.

The NHS explains that antibiotics can be given as tablets, as creams and drops, or as injections or drips directly into the blood, and that injections are used for more serious infections. Piperacillin with tazobactam falls into this last group. Because it is given by drip, it is a medicine that people meet on hospital wards and in emergency departments rather than from a pharmacy.

According to the patient leaflet, adults and adolescents can be given it for bacterial infections affecting the lower respiratory tract (the lungs), the urinary tract (kidneys and bladder), the abdomen, the skin or the blood. It may also be used for infections in people with low white blood cell counts, whose resistance to infection is reduced. In children aged 2 to 12 years the leaflet lists abdominal infections such as appendicitis, peritonitis and gallbladder infections, and infections in children with low white blood cell counts. It is not recommended for children under 2 years because there is not enough data on safety and effectiveness.

The leaflet also notes that in certain serious infections a doctor may combine it with other antibiotics. This is common in hospital practice when the cause of an infection is not yet known and the team wants to cover a broad range of possible bacteria.

The antibiotic is chosen before the exact bacterium is known. NICE calls this empiric therapy: an antibiotic given before a specific microorganism or source of infection is identified, usually a broad-spectrum one, which may be changed once the cause is confirmed. The NHS sepsis page describes the same approach, saying you may be given a general antibiotic to start with and then a more specific one after the cause of the infection has been confirmed.

Neutropenic sepsis is a medical emergency that can occur in people having anticancer treatment such as chemotherapy, because the number of infection-fighting white cells (neutrophils) can fall. NICE guideline CG151 says to treat suspected neutropenic sepsis as an acute medical emergency and to offer antibiotics immediately, without waiting for the cause to be known.

The same guideline recommends piperacillin with tazobactam as the initial antibiotic for people with suspected neutropenic sepsis who need intravenous treatment, unless there are patient-specific or local microbiological reasons to choose another. It advises against starting with an aminoglycoside antibiotic, either alone or as a pair, unless there is a specific indication. It also says not to routinely add a glycopeptide antibiotic in people with central venous access devices unless there is a specific reason.

CG151 recommends that people having anticancer treatment, and their carers, are given written and oral information about neutropenic sepsis and how to reach 24-hour specialist oncology advice. If you are having chemotherapy and develop a high temperature or feel unwell, the NHS chemotherapy pages say to contact your care team straight away, or NHS 111 if you are not sure how to reach them.

Once treatment has started, the guideline says the team should reassess the risk of complications within 24 hours. After 48 hours of treatment, people judged to be at low risk may be switched from intravenous to oral antibiotics, and discharge is only offered after a further reassessment. These are decisions for the hospital team, and they explain why a stay can be short for some people and longer for others.

The patient leaflet says you should not be given piperacillin with tazobactam if you are allergic to piperacillin, tazobactam, penicillins, cephalosporins or other beta-lactamase inhibitors. A previous reaction to any of these needs to be mentioned before the first dose. The NHS adds that some people have an allergic reaction to antibiotics, especially penicillins and cephalosporins, and that in very rare cases this can be a medical emergency.

The leaflet asks you to tell the team before treatment if you have kidney or liver problems, are on dialysis, have low potassium levels, are taking anticoagulants, or have had convulsions. It says doctors may check your kidneys before treatment and perform regular blood tests during it, particularly if the medicine is needed for a long time.

Several interactions are named. Giving it together with vancomycin may increase the risk of kidney injury, even in people with healthy kidneys. Probenecid, a gout medicine, can slow the removal of piperacillin from the body. Blood thinners such as heparin and warfarin, muscle relaxants used in anaesthesia, and methotrexate are also listed. The leaflet asks you to tell laboratory staff you are on this antibiotic if you give blood or urine samples, because it can affect some test results.

In pregnancy and breastfeeding the leaflet says the medicine can pass to the baby, and that the doctor will decide whether it is right for you. It is not expected to affect driving.

The leaflet separates milder effects from those that need immediate attention. Serious skin reactions can start as reddish target-like spots or circular patches, often with blisters, sometimes with ulcers in the mouth, nose or genitals and red, swollen eyes. A severe allergic condition involving the skin, kidney and liver is also described. Anyone who notices a spreading rash, blistering, chest pain with signs of allergy, unexplained muscle pain with dark urine, or unexpected bleeding while on a drip should tell a nurse or doctor at once.

The leaflet also asks you to report new or worsening infection, fever with swollen glands, bruising and weakness together, convulsions, and diarrhoea. Diarrhoea during or after antibiotics can be a sign of Clostridioides difficile infection, which the NHS explains is more likely in people who have recently taken antibiotics, particularly in hospital or care homes. Do not treat it with anti-diarrhoea medicine such as loperamide before speaking to staff, as the NHS says this can stop the infection clearing.

Because the drip is given by trained staff, you are unlikely to receive the wrong dose. The leaflet says that if you think you have missed a dose, or have been given too much, you should tell the nurse or doctor immediately. Report any suspected side effect to the team; the Yellow Card scheme run by the MHRA also lets patients report them.

The leaflet states the usual adult and adolescent dose is 4 g with 0.5 g given every 6 to 8 hours into a vein, and that children aged 2 to 12 receive a weight-based dose. People with kidney problems may need a lower dose or longer gaps between doses. These figures are for explanation only: the team calculates the dose individually.

Treatment continues until the signs of infection have gone, which the leaflet puts at 5 to 14 days. In practice, many people are switched to tablets once they improve, as NICE describes for neutropenic sepsis. If you are discharged on oral antibiotics, finish the course as prescribed, as the NHS advises for all antibiotics.

It may help to ask the team which infection is being treated, how long the drip is likely to continue, what blood tests are planned and what the plan is if you improve quickly.

Intravenous antibiotics such as this one are given on NHS wards and in NHS emergency departments, and private hospitals also use them for inpatients. The drug itself and the checks around it are the same. Serious infection and suspected sepsis are treated as emergencies, and the NHS says to call 999 or go to A&E if someone has signs of sepsis rather than waiting for an appointment.