Pipacycline is a semi-synthetic tetracycline formed by a Mannich condensation of formaldehyde and 4-hydroxyethyl piperazine with tetracycline. The introduction of the piperazine improves bioavailability, but Mannich bases are pro-drugs, converting back to the parent compound. Pipacycline is used commercially as a salt in combination with penicillin V for parenteral use (penimepicycline). Penimepicycline exerts a bactericidal action on the streptococci, and a bacteriostatic action on various gram-positive and gram-negative bacilli, as well as on the penicillin-resistant staphylococci.