Tienam i/v (Primaxin)

Primaxin is a carbapenem antibiotic. It kills bacteria by blocking growth of the bacteria's cell wall. It is used for treating serious infections of mild to moderate severity caused by certain bacteria.

Therapeutic actions:
Imipenem is mainly bactericidal. It inhibits the third and final stage of bacterial cell wall synthesis by preferentially binding to specific penicillin-binding proteins (PBPs) that are located inside the bacterial cell wall. Penicillin-binding proteins are responsible for several steps in the synthesis of the cell wall and are found in quantities of several hundred to several thousand molecules per bacterial cell. Penicillin-binding proteins vary among different bacterial species. Imipenem binds to all PBP subtypes but has highest affinity for PBP-2 and PBP 1B. At PBP-3, where cephalosporins bind, imipenem has minimal activity. Antimicrobial activity of imipenem is a result of binding to PBP-1A, PBP-1B, and PBP-2. Because little activity is exerted at PBP-3 (the protein responsible for bacterial septum formation), long, filamentous forms are not produced after imipenem exposure. PBP-2 is responsible for maintaining the rod-like shape. Binding of imipenem to PBP-2 causes bacteria to form spheroplasts or ellipsoidial cells without filament formation. Binding to PBP-1, which is responsible for formation of the cell wall, causes these cells to lyse rapidly. Lysis is mediated by bacterial cell wall autolytic enzymes (i.e., autolysins). The relationship between PBPs and autolysins is unclear, but it is possible that the beta-lactam antibiotic interferes with an autolysin inhibitor. Imipenem also has greater ability to penetrate the outer membrane of gram-negative bacteria than do the other beta-lactam antibiotics.

What is it used for?:
• Lower respiratory tract infections,including pneumonia and bronchitis as an exacerbation of COPD (chronic obstructive pulmonary disease);
• Intra-abdominal infections, including acute gangrenous or perforated appendicitis and appendicitis with peritonitis;
• Skin and skin structure infections, including abscesses, cellulitis, infected skin ulcers and wound infections;
• Gynecologic infections, including postpartum endomyometritis;

Contraindications and cautions:
• allergy to any ingredient in Primaxin , to any other carbapenem antibiotic (eg. meropenem), or to amide-type local anesthetics (eg. lidocaine);
• heart block or severe shock;
• taking probenecid;
• the patient is a child with a brain or nervous system infection, or weighs less than 66 lb (30 kg) and has kidney problems.

Side effects:
mild diarrhea; nausea; minor pain, swelling, or redness at the injection site; vomiting.

Interactions:
• Ganciclovir may increase the risk of seizures;
• Actions and side effects of Primaxin, such as heart or nerve toxicity, may be increased by amiodarone, beta-blockers (eg. propranolol), cimetidine, mexiletine, or probenecid;
• Primaxin may increase actions and side effects of succinylcholine;
• Valproic acid because effectiveness may be decreased by Primaxin IM
• Other medicines that may increase your risk of seizures (eg. tramadol) because the risk of seizures may be further increased when combined with Primaxin.