Issues for surgery
For hypertension – loss of blood pressure (BP) control and potential rebound hypertension if omitted (see Further information).
For menopausal symptoms – potential worsening of symptoms, particularly flushing and vasomotor conditions if omitted.
For prevention of vascular headache – potential recurrence of symptoms if omitted.
Risk of hypotension if continued.
Risk of bradycardia if continued.
Risk of Central Nervous System (CNS) depression if continued.
Advice in the perioperative period
Elective and emergency surgery
Continue – monitor BP.
Post-operative advice
Restart post-operatively once enteral intake resumed.
Monitor BP.
Interactions with common anaesthetic agents
Hypotension
Clonidine can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics.
Bradycardia
Clonidine has a dose dependent effect on bradycardia; the risk of bradycardia may be further increased when used concomitantly with the following:
- alfentanil, fentanyl or remifentanil
- neostigmine
- propofol
- suxamethonium
CNS depression
See also Interactions with other common medicines used in the perioperative period.
Clonidine has CNS depressant effects which may be additive with other medicines that also have CNS depressant effects such as:
- benzodiazepines
- inhalational anaesthetics and intravenous anaesthetics
- local anaesthetics
- opioids
(Consult British National Formulary for available drugs in each class)
Vasopressors
Studies found that pre-treatment with clonidine decreased the vasopressor response to small doses of dopamine and increased the response to dobutamine, ephedrine, isoprenaline and phenylephrine. Clonidine did not affect the response to noradrenaline/norepinephrine. The clinical significance of this interaction is not known but bear in mind the effect of dobutamine, ephedrine and phenylephrine may be potentiated in patients taking clonidine.
General anaesthetics
Studies found that premedication with clonidine significantly attenuates the cardiovascular responses (mean arterial pressure, heart rate and cardiac index) to hypercapnia in patients anaesthetised with propofol, but not with isoflurane.
Local anaesthetics
Studies suggest addition of clonidine may increase the response to bupivacaine without causing adverse cardiac effects and may reduce levels of lidocaine appearing in the plasma, following epidural administration. Both these interactions may be beneficial.
Interactions with other common medicines used in the perioperative period
Hypotension
Clonidine can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine.
CNS depression
See also Interactions with common anaesthetic agents.
Clonidine has CNS depressant effects which may be additive with other medicines that also have CNS depressant effects such as:
- antiemetics (e.g. cyclizine, prochlorperazine)
- opioids
(Consult British National Formulary for available drugs in each class)
Further information
Withdrawal
Clonidine should be withdrawn gradually as abrupt withdrawal after prolonged treatment with high doses can result in a rapid rise in blood pressure (rebound hypertension), agitation, restlessness, palpitations, nervousness, tremor, headache and nausea.
References
Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 5th February 2021]
Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 5th February 2021]
Summary of Product Characteristics – Clonidine Hydrochloride 25 microgram Tablets. Accord-UK Ltd. Accessed via www.medicines.org.uk 05/02/2021 [date of revision of the text July 2020]