Use in Postoperative or Obstetrical Analgesia

Clonidine hydrochloride (epidural clonidine) is not recommended for obstetrical, postpartum, or perioperative pain management. The risk of hemodynamic instability, especially hypotension and bradycardia, from epidural clonidine may be unacceptable in these patients.

Hypotension

Because severe hypotension may follow the administration of clonidine, it should be used with caution in all patients. It is not recommended in most patients with severe cardiovascular disease or in those who are otherwise hemodynamically unstable. The benefit of its administration in these patients should be carefully balanced against the potential risks resulting from hypotension.

Vital signs should be monitored frequently, especially during the first few days of epidural clonidine therapy. When clonidine is infused into the upper thoracic spinal segments, more pronounced decreases in the blood pressure may be seen.

Clonidine decreases sympathetic outflow from the central nervous system resulting in decreases in peripheral resistance, renal vascular resistance, heart rate, and blood pressure. However, in the absence of profound hypotension, renal blood flow and glomerular filtration rate remain essentially unchanged.

In the pivotal double-blind, randomized study of cancer patients, where 38 subjects were administered epidural clonidine hydrochloride at 30 mcg/hr in addition to epidural morphine, hypotension occurred in 45% of subjects. Most episodes of hypotension occurred within the first four days after beginning epidural clonidine. However, hypotensive episodes occurred throughout the duration of the trial. There was a tendency for these episodes to occur more commonly in women, and in those with higher serum clonidine levels. Patients experiencing hypotension also tended to weigh less than those who did not experience hypotension. The hypotension usually responded to intravenous fluids and, if necessary, parenteral ephedrine.

Published reports on the use of epidural clonidine for intraoperative or postoperative analgesia also show a consistent and marked hypotensive response to clonidine. Severe hypotension may occur even if intravenous fluid pretreatment is given.

Withdrawal

Sudden cessation of clonidine treatment, regardless of the route of administration, has, in some cases, resulted in symptoms such as nervousness, agitation, headache, and tremor, accompanied or followed by a rapid rise in blood pressure. The likelihood of such reactions appears to be greater after administration of higher doses or with concomitant beta-blocker treatment. Special caution is therefore advised in these situations. Rare instances of hypertensive encephalopathy, cerebrovascular accidents and death have been reported after abrupt clonidine withdrawal. Patients with a history of hypertension and/or other underlying cardiovascular conditions may be at particular risk of the consequences of abrupt discontinuation of clonidine. In the pivotal double-blind, randomized cancer pain study, four of 38 subjects receiving 720 mcg of clonidine per day experienced rebound hypertension following abrupt withdrawal. One of these patients with rebound hypertension subsequently experienced a cerebrovascular accident.

Careful monitoring of infusion pump function and inspection of catheter tubing for obstruction or dislodgement can help reduce the risk of inadvertent abrupt withdrawal of epidural clonidine. Patients should notify their physician immediately if clonidine administration is inadvertently interrupted for any reason. Patients should also be instructed not to discontinue therapy without consulting their physician.

When discontinuing therapy with epidural clonidine, the physician should reduce the dose gradually over 2 to 4 days to avoid withdrawal symptoms.

An excessive rise in blood pressure following discontinuation of epidural clonidine can be treated by administration of clonidine or by intravenous phentolamine. If therapy is to be discontinued in patients receiving a beta-blocker and clonidine concurrently, the beta-blocker should be withdrawn several days before the gradual discontinuation of epidural clonidine.

Infections

Infections related to implantable epidural catheters pose a serious risk. Evaluation of fever in a patient receiving epidural clonidine should include the possibility of a catheter-related infection such as meningitis or epidural abscess.