Cabapenems

Question 0

Imipenem

Imipenem+Cilastatin (Primaxin)

Answer 0

Poor oral abs. IM or IV
Metabolized in kidney and deactivated by dehydropeptidase I (opens up beta Lactam ring)=> give in combination with Cilistatin (dehydropeptidase inhibitor)
ADR: seizures from high concentration in pts. With renal insufficiency or CNS diseases

Question 1

Carbapenem

Answer 1

Inhibits peptidoglycan cross linking
Broad spectrum activity: alkyl thiol side chain gets partially positively charged at physiologic pH allowing activity against gram (-) bacteria
Penam structure: beta Lactam fused to five membered ring. Sulfur is exocyclic to five membered ring
Resistance to beta lactamase: hydroxyethyl side chain gives steric henderence. => drug of choice for ESBL
Poor oral absorption. IM, IV

Question 2

Meropenem (Merren), Ertapenem (Invanz)

Answer 2

Methy group at C4 confers dehydropeptidase resistance. Administered as single agents
Ertapenem is highly PPB=> longer T1/2, once daily dosing
Less incidence of seizures

Question 3

Doripenem (Doribax)

Answer 3

Resistance to dehydropeptidase b/c of methyl group at C4. Administered as single agent
Preferred drug in extended infusions b/c it is stable in solution for longer time than other carbapenems

Question 4

Cross allergenicity of PCN with carbapenems…

Answer 4

Can occur.

45%more likely with imipenem