Disposition of the opioid piritramide in newborns and infants

Currently there is no data available about pharmacokinetics and pharmacodynamics of piritramide in newborns and infants.

In these specific groups only small blood volumes can be collected. Therefore we developed an efficient method to determine piritramide by LC-MS/MS.

Based on the measured serum concentrations we investigated the pharmacokinetics after bolus application of piritramide (0,05mg/kg KG) in newborns and infants.

8 serum samples and 4 urine samples over 12h of each patient were analysed for piritramide. Pharmacokinetic parameters were calculated using a two compartment model for piritramide.

Pharmacokinetic parameters (median±SD):

group	dose	Cmax	t1/2α	t1/2β)	Vdss
	[mg]	[µg/l]	[min]	[min]	[l/kg]
1	0,16±0,012	79±240	37±57	702±720	2,0±4,93
2	0,30±0,129	36±367	8,4±5,1	157±102	1,7±2,5
3	0,54±0,25	11,6±81	13±10	160±68	7,0±5,2
4	0,96±0,51	15,5±8,7	18±11	166±143	6,7±2,2

group 1: newborns; group 2: 1–4months; group 3: 5–12months; group 4: 2–4years.

Elimination was considerably reduced in the newborn (t1/2: 12h). The distribution volume was small in the very young babies. In the age over 4 months Vdss was similar to those of adults, whereas the t1/2 was shorter compared to adults.