I know standard dosage for zidovudine for an infant born to an HIV positive mother is "2 mg/kg body weight q6h" as part of the MTCT prevention. In 6 weeks time however, an infant easily weighs a kilo, to 1.5 kg more which is up to 50% of its birth weight. How often do you have the infants checked for weight gain in order to change the dosage?

In our clinic, we usually see babies at 1 and 4 weeks to see how things are going, check their weights, and to draw bloods to check for infection. If weight is increased by more than 10% of the baby's previous weight, we adjust the dose. If weight is down at 1 week, we usually do not decrease the dose, since the baby is expected to grow -- any babies that lose weight over the first week are usually seen again at 2 weeks to re-check weights. Dose adjustment is relatively uncommon during the first week but fairly common at week 4 .