Meronem dose is easier than Tienam in renal failure

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.

NPS-adv

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.

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References

1. 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.
2. Pham PA, Bartlett JG. Imipenem/cilastatin. In: Johns Hopkins Antibiotics Guide (https://www.hopkinsguides.com/hopkins), Unbound Medicine, 2017
3. 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.

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