How the dose is calculated
Meropenem is dosed in mg/kg/day divided every 8 hours for standard infant/child and adult dosing. Severe infections including meningitis use a higher total daily dose at the same frequency. Neonates use a fixed mg/kg/dose (not a mg/kg/day figure) with the interval widened at younger postnatal age (PNA), reflecting immature renal clearance. This is an injectable (IV) antibiotic — no suspension volume conversion applies.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Standard (infant/child/adult) | 60 mg/kg/day | every 8h (3×/day) | 3000 mg/day |
| Severe/meningitis-range | 120 mg/kg/day | every 8h (3×/day) | 6000 mg/day |
| Neonate — PNA 0-7 days | 20 mg/kg/dose | every 12h | — |
| Neonate — PNA >7 days | 20 mg/kg/dose | every 8-12h* | — |
*For neonates older than 7 days, the interval is chosen based on gestational maturity and clinical severity — every 8 hours is commonly used and is what the calculator applies by default for this option; every 12 hours is used for more premature or clinically stable infants per local neonatal protocol. Meropenem is supplied as a powder for reconstitution (IV) — there is no oral suspension, so this calculator reports the mg dose only; follow your local pharmacy's reconstitution and infusion protocol for the actual volume to administer.
Meropenem dose adult vs pediatric
Adult dosing generally follows the same mg/kg/day tiers as above for weight-based prescribing, but adults are also commonly dosed with fixed doses (e.g. 500 mg-1 g every 8 hours standard, 2 g every 8 hours for meningitis/CNS or Pseudomonas) once weight-based dosing would reach the same range — the underlying total daily exposure is the same principle, just expressed as a fixed dose once a patient is large enough that mg/kg dosing plateaus at the standard adult amount. For renal impairment, both dose and/or interval need adjustment — see the Meropenem Renal Dose Adjustment Calculator.
Clinical use
- Meropenem's very broad spectrum (Gram-positive, Gram-negative including Pseudomonas, and anaerobes) makes it a common choice for severe hospital-acquired or multidrug-resistant infections — antibiotic stewardship principles apply strongly given the risk of driving further carbapenem resistance.
- Good CSF penetration and a favourable seizure-risk profile compared to imipenem make it a preferred carbapenem for CNS infections requiring this drug class.
- Cross-reactivity with penicillin allergy is low but not zero — use clinical judgement and allergy history when penicillin allergy is reported.
- Requires dose-interval adjustment in significant renal impairment — see the dedicated renal dose adjustment calculator for CrCl-based dosing.
- Ertapenem is sometimes confused with meropenem, but the two differ meaningfully: ertapenem has no reliable Pseudomonas or Acinetobacter coverage and is dosed once daily, making it useful for outpatient parenteral therapy, while meropenem covers Pseudomonas and is reserved for more severe or resistant infections needing broader cover.
Frequently asked questions
What is meropenem used for?
Meropenem is a broad-spectrum carbapenem antibiotic reserved for severe, hospital-acquired, or multidrug-resistant infections, including some cases of bacterial meningitis, where narrower-spectrum agents aren't sufficient.
Why is meropenem considered a 'reserve' antibiotic?
Its very broad spectrum makes it valuable for resistant infections, but overuse drives further carbapenem resistance — so it's generally reserved for situations where narrower-spectrum agents won't work, guided by antibiotic stewardship principles.
Can meropenem be used in penicillin allergy?
Cross-reactivity between carbapenems and penicillins is low but not zero — clinical judgement based on the type and severity of the reported allergy is needed, ideally with specialist input for significant allergy histories.
Is meropenem available as a tablet or syrup?
No — meropenem is only available as an injectable (IV) formulation; there is no oral tablet or suspension form.
What is the meropenem dose for a neonate?
20 mg/kg per dose — given every 12 hours in the first week of life (PNA 0-7 days), then every 8-12 hours from day 8 onward, with the interval chosen based on gestational maturity and clinical severity. This differs from the mg/kg/day model used for infants, children, and adults because neonatal renal clearance changes rapidly in the first weeks of life.
Does meropenem need renal dose adjustment?
Yes — significant renal impairment requires reducing the dose and/or extending the interval. Use the Meropenem Renal Dose Adjustment Calculator for CrCl-based adjustment rather than the standard weight-based dose on this page.
What is the difference between ertapenem and meropenem?
Ertapenem lacks reliable activity against Pseudomonas aeruginosa and Acinetobacter, and is dosed once daily — useful for once-daily outpatient IV therapy for infections where those organisms aren't a concern. Meropenem covers Pseudomonas and is generally reserved for more severe, resistant, or polymicrobial infections where broader cover is needed, at the cost of more frequent (every 8h) dosing.
References
- Tunkel AR, et al. Practice Guidelines for the Management of Bacterial Meningitis (IDSA). Clin Infect Dis. 2004.
- British National Formulary for Children (BNFc) — Meropenem.
- American Academy of Pediatrics Red Book — Carbapenems.