• Plasma level of Doxapram and its active metabolite (ketodoxapram) at 48 h after the onset of treatment. [ Time Frame: 48H ] [ Designated as safety issue: Yes ]
  

• Efficacy (rate of significant apnea) [ Time Frame: 1 Week ] [ Designated as safety issue: No ]
  

Drug: Doxapram
Dosing comparison between fixed scheduled and sex related dosage

Doxapram is a drug used to stimulate respiration in neonates prematurely born and failing to breathe. For a given dose, the fluctuations in concentrations of drug observed in infants' blood might be wide, leading to a risk of lack of efficacy of the treatment or of toxic effects. Two factors are linked to these fluctuations: age and gender. The aim of our study is to compare a dosage regimen based only on patient's weight, and another one using a dosing chart taking into account not only weight but also age and gender to prescribe the initial dose of doxapram. The final goal of this trial is to improve efficacy and tolerance of doxapram by minimizing the fluctuations in blood drug levels in premature neonates.

Inclusion Criteria:

• Premature infants (<37 weeks gestation)
• More than 1 significant Apnea q 8h (> 20 sec or < 20 sec with bradycardia or desaturation)
• Already treated with caffeine

Exclusion Criteria:

• Intubation
• congenital malformation
• symptomatic apnea