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Pentrex: Full Drug Profile

Medically reviewed by Min Clinic Staff | Updated: January 2026

Pentrex - General Information

Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic. [PubChem]

 

Pharmacology of Pentrex

Pentrex is a penicillin beta-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms. The name "penicillin" can either refer to several variants of penicillin available, or to the group of antibiotics derived from the penicillins. Pentrex has in vitro activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of Pentrex results from the inhibition of cell wall synthesis and is mediated through Pentrex binding to penicillin binding proteins (PBPs). Pentrex is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, and cephalosporinases and extended spectrum beta-lactamases.

 

Pentrex for patients

1. The patient should inform the physician of any history of sensitivity to allergens, including previous hypersensitivity reactions to penicillins and cephalosporins.

2. The patient should discontinue ampicillin and contact the physician immediately if any side effect occurs.

3. Ampicillin should be taken with a full glass (8 oz) of water, one-half hour before or two hours after meals.

4. Diabetic patients should consult with the physician before changing diet or dosage of diabetes medication.

 

Pentrex Interactions

When administered concurrently, the following drugs may interact with ampicillin.

Allopurinol: Increased possibility of skin rash, particularly in hyperuricemic patients may occur.

Bacteriostatic Antibiotics: Chloramphenicol, erythromycins, sulfonamides, or tetracyclines may interfere with the bactericidal effect of penicillins. This has been demonstrated in view, however, the clinical significance of this interaction is not well documented.

Oral Contraceptives: May be less effective and increased breakthrough bleeding may occur.

Probenecid: May decrease renal tubular secretion of ampicillin resulting in increased blood levels and/or ampicillin toxicity.

Drug/Laboratory Test Interaction

After treatment with ampicillin, a false-positive reaction for glucose in the urine may occur with copper sulfate tests (Benedict's solution, Fehling's solution, or Clinitest tablets) but not with enzyme based tests such as Clinistix and Glucose Enzymatic Test Strip USP.

 

Pentrex Contraindications

A history of a previous hypersensitivity reaction to any of the penicillins is a contraindication. Ampicillin is also contraindicated in infections caused by penicillinase-producing organisms.

 

Additional information about Pentrex

Pentrex Indication

For treatment of infection (Respiratory, GI, UTI and meningitis) due to E. coli, P. mirabilis, enterococci, Shigella, S. typhosa and other Salmonella, nonpenicillinase-producing N. gononhoeae, H. influenzae, staphylococci, streptococci including streptoc

Mechanism Of Action
By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, Pentrex inhibits the third and last stage of bacterial cell wall synthesis. Cell lysis is then mediated by bacterial cell wall autolytic enzymes such as autolysins; it is possible that Pentrex interferes with an autolysin inhibitor.
Drug Interactions
Methotrexate The penicillin increases the effect and toxicity of methotrexate
Food Interactions
Take on an empty stomach.
Generic Name
Ampicillin
Synonyms
Ampicilline [Inn-French]; Ampicillinum [Inn-Latin]; Ampicilline; Ampicillina [Dcit]; Ampicillin [Usan-Ban-Inn-Jan]; Ampicillin Trihydrate; Ampicillin Sodium; Ampicillin Base; Ampicillin Anhydrous; Ampicillin Anhydrate; Ampicillin Acid; Ampicilina [Inn-Spanish]; Anhydrous Ampicillin; Bayer 5427; D-Ampicillin; Aminobenzylpenicillin
Drug Category
Anti-Bacterial Agents; Penicillins
Drug Type
Small Molecule; Approved
Other Brand Names containing Ampicillin
AB-PC; Ab-Pc Sol; Acillin; Adobacillin; Alpen; Amblosin; Amcill; Amfipen; Amfipen V; Amipenix S; Ampen; Ampi; Ampi-Bol; Ampi-Co; Ampi-Tab; Ampichel; Ampicil; Ampicillin A; Ampicin; Ampifarm; Ampikel; Ampimed; Ampipenin; Ampipenin, Nt3; Ampiscel; Ampisyn; Ampivax; Ampivet; Amplacilina; Amplin; Amplipenyl; Amplisom; Amplital; Ampy-Penyl; Austrapen; BRL; Binotal; Bonapicillin; Britacil; Campicillin; Cimex; Copharcilin; D-Cillin; Delcillin; Deripen; Divercillin; Doktacillin; Duphacillin; Geocillin; Grampenil; Guicitrina; Guicitrine; Lifeampil; Morepen; Norobrittin; Novo-Ampicillin; Nuvapen; Olin Kid; Omnipen; Omnipen-N; Orbicilina; Pen A; Pen Ampil; Pen a Oral; Penbristol; Penbritin; Penbritin Paediatric; Penbritin Syrup; Penbritin-S; Penbrock; Penicline; Penimic; Pensyn; Pentrex; Pentrexl; Pentrexyl; Pfizerpen A; Pfizerpen-A; Polycillin; Polycillin-N; Ponecil; Princillin; Principen; Principen '125'; Principen '250'; Principen '500'; Qidamp; Racenacillin; Ro-Ampen; Rosampline; Roscillin; Semicillin; Semicillin R; Servicillin; Sk-Ampicillin; Spectrobid; Sumipanto; Supen; Synpenin; Texcillin; Tokiocillin; Tolomol; Totacillin; Totacillin-N; Totalciclina; Totapen; Trifacilina; Ultrabion; Ultrabron; Vampen; Viccillin; Viccillin S; Wypicil;
Dosage Forms of Pentrex
Powder, for solution Intramuscular
Chemical IUPAC Name
(2S,5R,6R)-6-[[(2R)-2-amino-2-phenylacetyl]amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
Chemical Formula
C16H19N3O4S
Organisms Affected
Enteric bacteria and other eubacteria