Drug Withdrawal and Milk Discard Times of Pencillins ^a

 

Penicillin	Species	Withdrawal Time (days)	Milk Discard Time (days)
Procaine penicillin G	Cattle	10 (at label dosage) 30 (at 20,000 lU/kg, bid)	3
	Sheep	9
	Pigs	7
Benzathine penicillin G	Cattle	30
Ampicillin		6
	Preruminant calves	15
Amoxicillin	Cattle	30	2

 

^a All administered IM

N.B : The most common mistake made with penicillin G is to think that the dose forms are interchangeable. You cannot substitute 10,000 IU/KG of procaine PenG SID for 10,000 IU/KG Kpen QID and expect the same activity. First, notice that the total daily dose is 1:4. Combine that with the change in peak concentrations and you’ve altered the activity profile considerably.