Is Tazact (piperacillin), a penicillin-based antibiotic?

Is Tazact a Penicillin?

Yes, Tazact (piperacillin-tazobactam) is a penicillin-based antibiotic—specifically, it combines piperacillin, a broad-spectrum ureidopenicillin, with tazobactam, a beta-lactamase inhibitor. 1

Chemical Classification and Structure

• Piperacillin is a semisynthetic penicillin derived from D(-)-α-aminobenzylpenicillin, making it definitively part of the beta-lactam penicillin family. 1

• The FDA describes piperacillin as a "semisynthetic broad-spectrum penicillin" with the chemical formula C23H26N5NaO7S. 1

• Tazobactam itself is not a penicillin but rather a beta-lactamase inhibitor that protects piperacillin from enzymatic degradation. 2

Clinical Implications of Penicillin Classification

Because Tazact contains piperacillin (a penicillin), it is absolutely contraindicated in patients with documented penicillin allergy. 1

• The FDA label explicitly states that piperacillin is "contraindicated in patients with a history of allergic reactions to any of the beta-lactams, including penicillins and/or cephalosporins." 1

• Patients with confirmed piperacillin-tazobactam hypersensitivity showed cross-reactivity with other penicillins in approximately one-third of cases, though two-thirds were selectively sensitized only to piperacillin-tazobactam. 3

• In rare cases (3 patients in one multicenter study), the allergic reaction may be specifically to the tazobactam component rather than the penicillin component. 3

Spectrum of Activity

As a penicillin, piperacillin-tazobactam provides broad coverage against gram-positive cocci, gram-negative bacilli (including Pseudomonas aeruginosa), and anaerobes. 4, 5

• The combination is more active than piperacillin alone because tazobactam inhibits Richmond and Sykes types II, III, IV, and V beta-lactamases, restoring activity against beta-lactamase-producing organisms. 2

• However, it does not cover MRSA, ESBL-producing Enterobacteriaceae (coverage is controversial and unreliable), or carbapenem-resistant organisms. 4

Common Clinical Pitfall

Do not assume that because a patient tolerates cephalosporins they can safely receive piperacillin-tazobactam—while cross-reactivity between penicillins and cephalosporins is lower than historically believed (approximately 1-3%), piperacillin-tazobactam remains a penicillin and requires appropriate allergy assessment. 6, 1