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The work incorporated in this thesis was conceived and carried out with the aim of investigating the efficacy and the incidence of side effects when different regimens for patient-controlled analgesia with morphine sulphate are used in children. Features of interest were the size of the bolus dose, the place of a background infusion and its magnitude, alternatives to the intravenous route of administration and the prevention of postoperative nausea and vomiting. In a comparison of patient-controlled analgesia with and without a background infusion there were no significant differences in the pain scores of the two groups although there were more side effects in the background group. There was also a better sleep pattern in this group. In a comparison of different background infusions, the inclusion of a background infusion of 4 micrograms kg^-1 hour^-1 did not increase the incidence of side effects and was associated with less hypoxaemia and a better sleep pattern than no background infusion although it did not improve the efficacy of the technique. When pain was assessed after movement, the inclusion of a background infusion of 4 micrograms kg^-1 hour^-1 improved analgesia and was associated with less hypoxaemia and a better sleep pattern than no background infusion. When bolus doses of 10 micrograms kg^-1 and 20 micrograms kg^-1 were compared, 20 micrograms kg^-1 produced lower pain scores and fewer hypoxaemic episodes than 10 micrograms kg^-1. There were no differences between the groups in the incidence of side effects. In comparison of intravenous and subcutaneous infusions for the treatment of postoperative pain there were no differences between the groups in pain scores or the incidence of side effects.

Several studies in the literature suggest that the biotransformation of foreign compounds in man is more similar to that in the non-human primate than to that in other laboratory animal species. However, published information about the pharmacokinetics of foreign compounds in non-human primates is limited and usually derived from one species, the rhesus monkey. In view of the often limited availability of this species for use in the development and safety evaluation of new drugs, pesticides, etc., it is necessary to search for potential replacement species for future use. This thesis compares the pharmacokinetics of seven well-known or commonly used drugs, i.e. antipyrine, diazepam, frusemide, ibuprofen, isosorbide dinitrate, paracetamol and pentobarbitone in the rhesus monkey, cynomolgus monkey and baboon with a view to defining further the suitability of these species for the study of newer substances. These three non-human primate species are those that are most frequently used in pharmacology and toxicology studies. The drugs were chosen for study because they are extensively used clinically and related human pharmacokinetic data are available for comparison.