TABLE 65-2. Penicillin Allergy-Oral Desensitization
Protocol for Patients with a Positive Skin Test Penicillin V Amountb Cumulative Dosea (units/mL) mL Units Dose (units) 1 1000 0.1 100 100 2 1000 0.2 200 300 3 ·1000 0.4 400 700 4 1000 O.S 800 1500 5 1000 1.6 1600 3100 6 1000 3.2 3200 6300 7 1000 6.4 6400 12,700 8 10,000 1.2 12,000 24,700 9 10,000 2.4 24,000 4S,700 10 10,000 4.S 4S,OOO 96,700 11 SO,OOO 1.0 80,000 176,700 12 80,000 2.0 160,000 336,700 13 SO,OOO 4.0 320,000 656,700 14 SO,OOO 8.0 640,000 1,296,700 alnterval between doses: 15 Elapsed time: 3 hours and 45 minutes. Cumulative dose: 1.3 million units.
Observation period: 30 minutes before parenteral adminis tration of penicillin.
bThe specific amount of drug was diluted in approximately 30 mL of water and administered orally.
From Wendel, 1985, with permission.
Distinct from allergy, a Jarisch-Herxheimer reaction develops following penicillin treatment in most women with primary syphilis and approximately half with secondary infection. Uterine contractions, mild maternal temperature elevation, decreased fetal movement, and fetal heart rate decelerations are findings. Reaction treatment is supportive with antipyretics as needed, hydration, and oxygen supplementation (Klein, 1990). In a study of 50 gravidas who received benzathine penicillin for syphilis, Myles and associates (1998) reported a 40-percent incidence of Jarisch-Herxheimer reactions. Of the 31 women monitored electronically, 42 percent developed regular uterine contractions, and 39 percent developed variable decelerations. All contractions resolved within 24 hours of therapy. Accordingly, for fetuses of viable age, some recommend administering the irst dose of antibiotic in labor and delivery and with continuous fetal monitoring for at least 24 hours (Rae, 2017). Others recommend this only if sonographic signs of fetal syphilis, described earlier, are found (Duf, 2014; Wendel, 2002). If this second plan is elected, patients are counseled on reaction signs and encouraged to seek evaluation if they develop.