OBJECTIVES: To evaluate the evidence for the effectiveness of clonidine, when given as a premedication, in reducing postoperative pain in children less than 18 years of age. We also sought evidence of any clinically significant side effects.

SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 12, 2012), Ovid MEDLINE (1966 to 21 December 2012) and Ovid EMBASE (1982 to 21 December 2012), as well as reference lists of other relevant articles and online trial registers.

SELECTION CRITERIA: We included all randomized (or quasi-randomized), controlled trials comparing clonidine premedication to placebo, a higher dose of clonidine, or another agent when used for surgical or other invasive procedures in children under the age of 18 years and where pain or a surrogate (principally the need for supplementary analgesia) was reported.

DATA COLLECTION AND ANALYSIS: Two authors independently performed the database search, decided on the inclusion eligibility of publications, ascertained study quality and extracted data. They then resolved any differences between their results by discussion. The data were entered into RevMan 5 for analyses and presentation. Sensitivity analyses were performed, as appropriate, to exclude studies with a high risk of bias.

MAIN RESULTS: We identified 11 trials investigating a total of 742 children in treatment arms relevant to our study question. Risks of bias in the studies were mainly low or unclear, but two studies had aspects of their methodology that had a high risk of bias. Overall, the quality of the evidence from pooled studies was low or had unclear risk of bias. Four trials compared clonidine with a placebo or no treatment, six trials compared clonidine with midazolam, and one trial compared clonidine with fentanyl. There was substantial methodological heterogeneity between trials; the dose and route of clonidine administration varied as did the patient populations, the types of surgery and the outcomes measured. It was therefore difficult to combine the outcomes of some trials for meta-analysis.When clonidine was compared to placebo, pooling studies of low or unclear risk of bias, the need for additional analgesia was reduced when clonidine premedication was given orally at 4 µg/kg (risk ratio (RR) 0.24, 95% confidence interval (CI) 0.11 to 0.51). Only one small trial (15 patients per arm) compared clonidine to midazolam for the same outcome; this also found a reduction in the need for additional postoperative analgesia (RR 0.25, 95% CI 0.09 to 0.71) when clonidine premedication was given orally at 2 or 4 µg/kg compared to oral midazolam at 0.5 mg/kg. A trial comparing oral clonidine at 4 µg/kg with intravenous fentanyl at 3 µg/kg found no statistically significant difference in the need for rescue analgesia (RR 0.89, 95% CI 0.56 to 1.42). When clonidine 4 µg/kg was compared to clonidine 2 µg/kg, there was a statistically significant difference in the number of patients requiring additional analgesia, in favour of the higher dose, as reported by a single, higher-quality trial (RR 0.38, 95% CI 0.23 to 0.65).The effect of clonidine on pain scores was hard to interpret due to differences in study methodology, the doses and route of drug administration, and the pain scale used. However, when given at a dose of 4 µg/kg, clonidine may have reduced analgesia requirements after surgery. There were no significant side effects of clonidine that were reported such as severe hypotension, bradycardia, or excessive sedation requiring intervention. However, several studies used atropine prophylactically with the aim of preventing such adverse effects.

SIGNIFICANCE: A strong need exists for the development of transdermal patch having improved bioavailability at the site of action with fewer side effects at off-target organs.

METHODS: The patches were physically characterized by texture analysis (color, flexibility, smoothness, transparency, and homogeneity), in vitro dissolution test and FTIR analysis. Furthermore, functional properties essential for TDDS, in vitro percentage of moisture content, percentage of water uptake, in vitro permeation by following different kinetic models, in vivo drug content estimation and skin irritation were determined using rabbit skin.

RESULTS: The optimized patches were soft, of uniform texture and thickness as well as pliable in nature. Novel transdermal patch showed ideal characteristics in terms of moisture content and water uptake. FTIR analysis confirmed no interaction between TZH and cellulose acetate phthalate (CAP). The patch showed sustained release of the drug which increased the availability of short acting TZH at the site of action. The patch also showed its biocompatibility to the in vivo model of rabbit skin.

METHODS: The authors randomized 10,010 patients with or at risk of atherosclerosis and scheduled for noncardiac surgery in a 1:1:1:1 ratio to clonidine/aspirin, clonidine/aspirin placebo, clonidine placebo/aspirin, or clonidine placebo/aspirin placebo. Patients started taking aspirin or placebo just before surgery; those not previously taking aspirin continued daily for 30 days, and those taking aspirin previously continued for 7 days. Patients were also randomly assigned to receive clonidine or placebo just before surgery, with the study drug continued for 72 h.

RESULTS: Neither aspirin nor clonidine had a significant effect on the primary 1-yr outcome, a composite of death or nonfatal myocardial infarction, with a 1-yr hazard ratio for aspirin of 1.00 (95% CI, 0.89 to 1.12; P = 0.948; 586 patients [11.8%] vs. 589 patients [11.8%]) and a hazard ratio for clonidine of 1.07 (95% CI, 0.96 to 1.20; P = 0.218; 608 patients [12.1%] vs. 567 patients [11.3%]), with effect on death or nonfatal infarction. Reduction in death and nonfatal myocardial infarction from aspirin in patients who previously had percutaneous coronary intervention at 30 days persisted at 1 yr. Specifically, the hazard ratio was 0.58 (95% CI, 0.35 to 0.95) in those with previous percutaneous coronary intervention and 1.03 (95% CI, 0.91to 1.16) in those without (interaction P = 0.033). There was no significant effect of either drug on death, cardiovascular complications, cancer, or chronic incisional pain at 1 yr (all P > 0.1).