As a clinical pharmacy specialist, doctors will often ask you about the difference between Meronam and Tienam. And how to adjust the doses of each in patients with kidney impairment...
Imipenem (Tienam) is the first carbapenem, was marketed in 1987. It is more active against Gram-positive cocci. While meropenem (Meronem) is more active against Gram-negative bacilli. The agents display similar pharmacokinetics. Clinical studies in patients with serious infections (intra-abdominal infection, respiratory infection, sepsis, febrile neutropenia) report similar bacteriological and clinical cure rates with imipenem and meropenem. Meropenem is approved for the treatment of bacterial meningitis, whereas imipenem is not, DUE TO risk of seizures.
Both can decrease valproic acid (Depakene) levels, and monitoring of valproic acid (Depakene) levels is recommended during concomitant use, and should be dose-reduced in the setting of renal dysfunction. You will notice that Meronem doesn't contain cilastatin or a similar enzyme inhibitor like Tienam does. Tienam contains cilastatin to prevent the conversion of imipenem to a toxic metabolite in the kidney. Meronem doesn't need cilastatin because it isn't metabolized by this same enzyme. It is easier to adjust the doses of Meronem than with Tienam (see Table 1) in patients with kidney impairment.
| Table (1). Comparative Note of Imipenem and Cilastatin (Tienam) and Meropenem Dose Adjustment in Patients with Altered Renal Functions | ||||
|---|---|---|---|---|
| Drug | Infection | CrCl (mL/minute) | Adult dose | Frequency |
| Imipenem-cilastatin (Tienam) | Moderate infection | >70 to 89 | 500 mg | Every 6 hours |
| 41 to 70 | 500 mg | Every 8 hours | ||
| 21 to 40 | 250 mg | Every 6 hours | ||
| <21 | 250 mg | Every 12 hours | ||
| iHD | 250 mg | Every 12 hours; administer after iHD on dialysis days | ||
| CRRT | 250 to 500 mg | Every 6 to 8 hours | ||
| Severe infection | >70 to 89 | 1 g | Every 6 to 8 hours | |
| 41 to 70 | 500 mg | Every 6 hours | ||
| 21 to 40 | 500 mg | Every 8 hours | ||
| <21 | 500 mg | Every 12 hours | ||
| iHD | 500 mg | Every 12 hours; administer after iHD on dialysis days | ||
| CRRT | 500 mg | Every 6 to 8 hours | ||
| Meropenem (Meronem) | Meningitis | >50 | 2 g | Every 8 hours |
| 26 to 50 | 2 g | Every 12 hours | ||
| 10 to 25 | 1 g | Every 12 hours | ||
| <10 | 1 g | Every 24 hours | ||
| iHD | 1 g | Every 24 hours; administer after iHD on dialysis days | ||
| CRRT | 500 mg or 1 g | Every 8 to 12 hours | ||
| Moderate to severe infection | >50 | 1 g | Every 8 hours | |
| 26 to 50 | 1 g | Every 12 hours | ||
| 10 to 25 | 500 mg | Every 12 hours | ||
| <10 | 500 mg | Every 24 hours | ||
| iHD | 500 mg | Every 24 hours; administer after iHD on dialysis days | ||
| CRRT | 500 mg or 1 g | Every 8 to 12 hours | ||
| CrCl: creatinine clearance; iHD: intermittent hemodialysis; CRRT: continuous renal replacement therapy; MDRD: Modification of Diet in Renal Disease; eGFR: estimated glomerular filtration rate. | ||||
REFERENCES
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Zhanel GG, Simor AE, Vercaigne L, Mandell L; Canadian Carbapenem Discussion Group. Imipenem and meropenem: Comparison of in vitro activity, pharmacokinetics, clinical trials and adverse effects. Can J Infect Dis. 1998 Jul;9(4):215-28. Available at: https://pubmed.ncbi.nlm.nih.gov/22346545
Pham PA, Bartlett JG. Imipenem/cilastatin. In: Johns Hopkins Antibiotics Guide (https://www.hopkinsguides.com/hopkins), Unbound Medicine, 2017
Zhanel GG, Wiebe R, Dilay L, Thomson K, Rubinstein E, Hoban DJ, Noreddin AM, Karlowsky JA. Comparative review of the carbapenems. Drugs. 2007;67(7):1027-52. Available at: https://pubmed.ncbi.nlm.nih.gov/17488146