Sulfonamides and Other Antibiotics

Reactions to sulfonamides (particularly rashes) are common in the general US population. There is marked accentuation of these rates in the patient with HIV infection. In particular, with TMP-SMX, which is frequently used for the treatment and prophylaxis of Pneumocystis carinii pneumonitis, the reaction rates are as follows: general population 3%, immunodeficient patients (HIV-seronegative) 12%, AIDS patients (HIV-seroposi-

Table 7

Oral Penicillin Desensitization Protocol

Table 7

Oral Penicillin Desensitization Protocol

Desensitization dosea

Stock drug, 250 mg/5 mL concentration

mL

Oral dosea mg

1

0.5 mg/mL

0.05

0.0025

2

0.10

0.05

3

0.20

0.10

4

0.40

0.20

5

0.80

0.40

6

5.0 mg/mL

0.15

0.75

7

0.30

1.50

8

0.60

3.

9

1.20

6.

10

2.40

12.

11

50 mg/mL

0.50

25

12

1.20

60

13

2.50

125

14

5.0

250

"Dose increased approximately every 20 min unless reaction occurs; then adjust accordingly.

"Dose increased approximately every 20 min unless reaction occurs; then adjust accordingly.

tive) 29-70%. Sulfa drugs are also likely to be associated with EM minor, SJS, and TEN types of reactions.

The allergic-like reaction to sulfonamides is not felt to be IgE mediated or, for that matter, an immune event. Unfortunately, there is no skin test or in vitro blood test to confirm a suspected reaction. In almost all cases, strict avoidance of the drug is recommended once a presumptive diagnosis has been made.

The exception is life-threatening situations, such as in patients with AIDS with P. carinii infection. In some cases the infection can be successfully treated with antimicrobial agents other than the TMP-SMX, such as inhaled pentamidine. In other cases, this is not possible, and TMP-SMX is the optimal drug for treatment of active infection and/or use in P. carinii prophylaxis.

In some cases adults with a documented history of a prior rash to TMP-SMX have later been given full doses of TMP-SMX without subsequent reaction. In other cases, serious reactions have resulted from this "full-dose" challenge.

Extended oral TMP-SMX desensitization procedures have proved successful in a limited series of patients: 10-23 d (19/21 patients); 10 d (23/28 patients); 2 d (6/7 patients). Use of full-dose challenge or desensitization is not advised for any patient who has a prior history of drug-associated erythema multiform, SJS, or TEN. The management of these situations is best left to the allergist/immunologist or an infectious disease specialist. Recent evidence would indicate that individuals who develop a rash to sulfonamide antibiotics are not at risk for a reaction to sulfonamide containing nonantibiotic drugs because of cross-reactivity, but may be a risk because of having multiple drugs sensitivity (see Suggested Reading, Storm et al.).

Documented allergic-like reactions to other antibiotics are uncommon. Usually they are not life threatening in nature. Most reactions to iv vancomycin result in a red flush ("red man syndrome") resulting from direct histamine release and can be controlled symptomatically and with adjustment of the iv drug administration rate. Occasionally serious allergic reactions can occur to ciprofloxin, and if this occurs quinolone-type antibiotics should be avoided.

In the case of reactions to other antibiotics, in almost all situations long-term avoidance is usually recommended, and the event is documented in the patient's records. Since there are usually substitute antibiotics available, it is not a problem for most individuals.

In a few individuals, however, multiple antibiotic sensitivities of different types occur. This type of patient presents a problem when the primary care physician tries to treat common infections. In most cases, P-lactam antibiotics are involved, so penicillin skin testing can be done. (Often the tests are negative.) There are no convenient tests for reactions involving other antibiotics. Reproducible reactions of any kind, especially those that are systemic in nature, are unusual. If the history of reaction is minor and the drug is necessary for therapy, a graded oral challenge can usually be done without difficulty to prove the safety of this alternative antibiotic (see Graded Drug Challenge Test Dosing).

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