The purpose of this study is to determine whether providing zidovudine (ZDV) and didanosine (ddI) during labor and for one month postpartum can reduce the selection of nevirapine (NVP) resistance mutations postpartum in women who received a single dose of nevirapine during labor and standard ZDV prophylaxis for the prevention of mother to child transmission of HIV.

A single nevirapine dose to the mother, with or without a dose to the child, in addition to oral ZDV prophylaxis starting from 28 weeks gestation has been proven to be highly effective in reducing further mother-to-child HIV transmission (PMTCT).

However, post exposure nevirapine resistance mutations are observed in the mother's viral population. These mutations detectable very early after exposure tend to disappear over time.

Nevertheless, they may be associated with decrease in efficacy of non-nucleoside reverse transcriptase inhibitor (NNRTI) containing regimens subsequently given to the women for their own health.

Therefore, there is a need for research to prevent selection of resistance in the first place or to overcome the resistance in subsequent treatment of the infected mother or infant.

Nevirapine plasma levels above IC50 have been detected in women exposed to a single 200 mg dose of nevirapine in a significant number of women during the third week postpartum.

We hypothesize that giving ZDV+ddI to women exposed to nevirapine for one month as soon as possible after exposure may prevent the selection of nevirapine resistance mutations.

Inclusion Criteria:

• Meet all pre-entry criteria;

• Consent to participate and to be followed for the duration of the study;

• Present the following laboratory values within 14 days prior to inclusion:

  • Hemoglobin > 8.0 mg/dl
  • Absolute neutrophil count > 1000 cells/mm3
  • Platelets > 100,000 cells/mm3
  • Serum creatinine < 1.5 mg/dl (women with a serum creatinine > 1.5 mg/dl must have a measured eight-hour urine creatinine clearance > 70 ml/min)
  • SGPT less than 10 times the upper limit of normal
  • Amylase less than 150/L IU (this upper limit may change slightly depending on the normal range at the hospital laboratory).

Exclusion Criteria:

• Evidence of pre-existing fetal anomalies incompatible with life;
• Known hypersensitivity to any benzodiazepine or to NVP;
• Receipt of antiretroviral agent other than ZDV;
• Receipt of non-allowed concomitant treatment or contraindication to ddI
• Concurrent participation in another clinical trial;
• Women with a CD4 count <200/µL or history of oral candidiasis if they are not receiving pneumocystis carinii pneumonia (PCP) prophylaxis
• Any other contra-indicated drugs during ZDV+ddI treatment for the mother as well as the child (Contra-indicated drugs such as gancyclovir, isoniazid, linezolid, ethambutol, rifabutin, cidofovir are not allowed during the ZDV ddI treatment after delivery in order to prevent pharmacological interactions or overlapping toxicities.)