By the PharmaTradz BD Team. Published November 2026.
When a patient has an infection caused by bacteria resistant to carbapenems, the usual "antibiotics of last resort", doctors turn to a small group of medicines that WHO calls the Reserve antibiotics. They are among the most important medicines a hospital can hold, and among the hardest to buy: volumes are small, prices are high, few companies make them, and in many countries they are not registered at all.
This guide is for hospital procurement teams, distributors and manufacturers. It explains which medicines are in the Reserve group, why supply is so uneven, and what to check when sourcing them. It is not clinical advice; prescribing decisions belong to the treating team and local stewardship programmes.
What "Reserve" means
WHO's AWaRe system sorts antibiotics into three groups. Access antibiotics are first-line treatments for common infections. Watch antibiotics carry a higher risk of resistance and are monitored. Reserve antibiotics are kept for confirmed or strongly suspected infections with multidrug-resistant organisms, so that resistance to them develops as slowly as possible.
The Reserve group includes the newer beta-lactam combinations, older drugs that have come back into use because resistance left few alternatives, and a handful of other last-line agents. The ones procurement teams ask us about most often are:
| Medicine | Main use | Supply picture |
|---|---|---|
| Ceftazidime-avibactam | KPC and OXA-48 producing Enterobacterales; with aztreonam for NDM | Originator plus a growing number of registered generics |
| Ceftolozane-tazobactam | Multidrug-resistant Pseudomonas | Originator only in major markets |
| Meropenem-vaborbactam | KPC-producing Enterobacterales | Originator only |
| Polymyxin B and colistin | Carbapenem-resistant Acinetobacter, Pseudomonas, Klebsiella | Off-patent, several manufacturers, quality varies |
| Cefiderocol, fosfomycin (IV), tigecycline, linezolid | Specific resistant infections | Mixed: from originator-only to widely generic |
Why supply is so uneven
Small, unpredictable volumes. Good stewardship means these drugs are used as little as possible. That is the right clinical choice, but it gives manufacturers little reason to register them in more countries or hold stock locally.
Registration gaps. The newer combinations are registered mainly in North America, Europe, Japan and a few large emerging markets. Many hospitals elsewhere can only obtain them through named-patient or special-import routes, one order at a time.
Access programmes are still young. Not-for-profit initiatives led by GARDP have licensed the right to make generic versions of some newer antibiotics, such as ceftazidime-avibactam and cefiderocol, for supply to a list of low- and middle-income countries. Generic ceftazidime-avibactam has started to receive approvals in several of those markets, but coverage is still patchy.
Older drugs, variable quality. Polymyxin B and colistin are cheap and widely made, but potency, impurity profiles and labelling (units versus milligrams) vary between sources. Buying on price alone is risky.
What to check when sourcing
- Registration or import route. Is the product registered in your country? If not, which route applies: named-patient import, a special import permit, or a shortage pathway? Who will be the importer of record?
- Proof of quality. For off-patent products, ask for a GMP certificate, a CoPP, batch certificates of analysis including potency and bacterial endotoxins, and compliance with the USP or EP monograph. For originator products, ask for evidence that the supply is authorised.
- Storage and shelf life. Some products, such as ceftolozane-tazobactam and polymyxin B vials, are kept refrigerated; others are stored at room temperature. Confirm remaining shelf life at dispatch and plan cold chain where needed.
- Dose maths. Order in vials per patient per day, not "doses". Meropenem-vaborbactam, for example, needs two vials for each dose, three times a day.
- Stewardship fit. Agree with your infectious diseases or microbiology team which agents your local resistance pattern actually needs before buying stock.
Where demand is growing
We see steady enquiries for Reserve antibiotics from hospitals and distributors in South and South-East Asia, the Middle East, Latin America and Eastern Europe, where carbapenem resistance is common and registered options are few. Many of these purchases run through hospital tenders or through the special-route purchases we track on our special import and emergency tenders page.
If you need a Reserve antibiotic for a hospital, a tender or a distributor portfolio, send us the product, quantity and destination. We confirm the registration or import route first, then match you with GMP-certified manufacturers or authorised originator supply, with the documents your regulator will ask for.
Frequently Asked Questions(FAQs)
What are Reserve antibiotics?
Antibiotics that WHO's AWaRe classification keeps for confirmed or strongly suspected infections with multidrug-resistant bacteria, such as ceftazidime-avibactam, meropenem-vaborbactam, cefiderocol, polymyxin B and colistin.
Why are Reserve antibiotics hard to source?
Volumes are small because their use is restricted, many are registered in only a few countries, and some are made only by the originator. Hospitals elsewhere often need named-patient or special-import permits.
Are generic versions available?
For older agents such as polymyxin B, colistin, linezolid and tigecycline, yes. For newer combinations it varies: generic ceftazidime-avibactam is registered in a growing number of countries, while ceftolozane-tazobactam and meropenem-vaborbactam are still supplied by the originators in major markets.
What documents should a buyer ask for?
A GMP certificate, a Certificate of a Pharmaceutical Product, batch certificates of analysis including potency and endotoxins, pharmacopoeia compliance, stability data and remaining shelf life, plus proof of authorised supply for originator products.
