PERSISTENCE OF PENICILLIN IN MILK 
Concentration: 84-96 Hours after One Udder Infusion 
Procaine Oil(P),AMS References: 33 
, Oil (M) ,AMS 37 
Sodium Water - Oil 
Ointment 
Oil (M) ,AMS 
Oint., 
Oil, 
Oil (M), 
Benzathine 
Sodium 
BPE 
@) @) 0.20 0.30 
* GIVEN AS SODIUM OR POTASSIUM SALTS AVERAGE UNITS OF PENICILLIN /ML. 
ABBREVIATIONS: WATER-OIL, WATER-IN-OIL EMULSION; OIL(P), PEANUT OIL; OIL(M), MINERAL OIL, 
OINT., OINTMENT; AMS, ALUMINUM MONOSTEARATE; BPE, N-BENZYL-2 PHENYLETHYLAMINE 
U. S. DEPARTMENT OF AGRICULTURE AGRICULTURAL RESEARCH SERVICE 
BN- 10707-X 
Figure 3,--Udder infusion: The average concentration of penicillin in milk when oil base vehicles were used and the residue lasted 
longer than 72 hours, 
Penicillin--The persistence of penicillin in milk when various salts, vehicles, and 
doses were used is illustrated in figure 5. The penicillin products can be classified in the 
order of increasing persistence in milk as follows: (1) Sodium or potassium penicillin G 
in aqueous suspensions, (2) diethylaminoethylester penicillin G hydriodide, (3) procaine 
penicillin G in aqeuous suspenion, (4) procaine penicillin G in oil, and (5) benzathine 
penicillin G and V in aqueous suspension. Thelevels of penicillin in the milk several days 
after injection of the long persisting products were relatively low. For instance, 96 hours 
after injection of the procaine penicillin G in oil and the benzathine penicillin G, the 
average concentrations were 0.02 u./ml. of milk (82). 
A direct relationship between the doseandthe persistence of penicillin is also shown, 
although it is very slight for the first two products. A comparison of the procaine peni- 
cillin G in aqueous suspension and in oil demonstrates the marked effect oil has on the 
persistence of penicillin. In most instances, three successive injections at 24-hour inter- 
vals did not cause an increase in the time penicillin persisted after the last injection 
(28,82). None of the animals showed maximal times of persistence that exceeded those 
shown in figure 5. Although penicillin was not found in the milk of cows given intra- 
muscular or intravenous injections of 1 million units or less (2,61,77), recent work (82) 
has shown that penicillin also did not appear in the milk of some cows injected intra- 
muscularly with benzathine penicillin G at doses of 2,000 u./lb. of body weight and with 
procaine penicillin G in oil at doses as high as 5,000 u./1b. of body weight. 
K93 
