Dipyridamole


  Issues for Surgery


Risk of ischaemic event if omitted.


  Advice in the Perioperative period


Elective and Emergency Surgery

Dipyridamole Alone or in Combination with Aspirin
Continue – including combination products.

Combination product: -

  • Molita® – contains dipyridamole 200mg and aspirin 25mg

EXCEPT:

  • procedures associated with high risk of bleeding or complications of bleeding (e.g. spinal surgery, some ophthalmological and neurosurgical procedures), consider stopping the day before surgery (see Further Information).

NB: For patients taking aspirin - also see Aspirin monograph.

Dipyridamole in Combination with Oral Anticoagulation
Continue.

 EXCEPT:

  • procedures associated with high risk of bleeding or complications of bleeding (e.g. spinal surgery, some ophthalmological and neurosurgical procedures), consider stopping the day before surgery (see Further Information).

NB: For patients taking warfarin – also see Warfarin monograph.

NB: For patients taking DOACs – also see Direct Oral Anticoagulant (DOACs) monograph.

Post-operative Advice

Resume usual treatment post-operatively, unless otherwise advised by a Haematologist.


  Interaction(s) with Common Anaesthetic Agents


Hypotension

Dipyridamole can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics1.


  Interaction(s) with other Common Medicines used in the Perioperative Period


Adenosine

Dipyridamole increases the plasma level and cardiovascular effects of adenosine1, 2, 3, 4. The adenosine bolus dose necessary to convert supraventricular tachycardia (SVT) to sinus rhythm is reduced by about fourfold2. Avoid or use initial bolus adenosine of 500 mcg or 1 mg in SVT2.

Hypotension

Dipyridamole can increase the risk of hypotension when used concomitantly with droperidol or prochlorperazine1.

Low Molecular Weight Heparin (LMWH) / Unfractionated Heparin (UFH)

LMWH / UFH is predicted to increase the risk of bleeding events when given with dipyridamole2, 3, 4.

Aspirin (contained in Molita®) has been show to increase the risk of bleeding when given with anticoagulants (e.g. heparin)5.

Corticosteroids

Concomitant use of corticosteroids with Molita® can increase the risk of gastrointestinal side effects due to the aspirin component5.

Non-Steroidal Anti-inflammatory Drugs (NSAIDs)

Concomitant use of NSAIDs with dipyridamole can increase the risk of bleeding1.

Concomitant use of NSAIDs with Molita® can increase the risk of gastrointestinal side effects due to the aspirin component5.

Drugs that Reduce Gastric pH

Proton pump inhibitors (PPIs) are predicted to decrease the absorption of dipyridamole (immediate release tablets)1. It is expected that other drugs that raise the gastric pH (e.g. histamine H2-antagonists [H2RAs], antacids) may reduce the bioavailability of dipyridamole (from tablets or suspension formulations)2, 3. The clinical significance of this interaction is unclear2. Single pre-operative doses of a PPI or H2RA should not pose a problem, but consider the interaction if prolonged use of PPI/H2RA is required post-operatively in patients not previously taking these medicines.

NB: Modified-release (MR) preparations of dipyridamole (that are buffered) do not appear to be affected2. Most patients being treated with dipyridamole are likely to be on the MR preparation. The standard release preparations are rarely used anymore due to a change in the evidence base.


  Further Information


Bleeding Risk

Daily use of dipyridamole does not alter bleeding times or laboratory platelet aggregation; nor does it appear to increase blood loss significantly during surgical procedures. Hence, unless the bleeding risk from the procedure is deemed exceptionally high, dipyridamole need not be stopped perioperatively6.

Addition of dipyridamole to aspirin does not increase the incidence of bleeding events4, 5. When dipyridamole was administered concomitantly with warfarin, bleeding was no greater in frequency or severity than that observed when warfarin was administered alone4, 5.

 

  References


  1. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 2nd August 2019]
  2. Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 26th July 2019
  3. Dipyridamole. In: Brayfield A (Ed), Martindale: The Complete Drug Reference. London: The Royal Pharmaceutical Society of Great Britain. http://www.medicinescomplete.com [Accessed 2nd August 2019]
  4. Summary of Product Characteristics – Ofram® (dipyridamole) PR 200mg Prolonged Release Hard Capsules. ADVANZ Pharma. Accessed via www.medicines.org.uk 02/08/2019 [date of revision of the text July 2019]
  5. Summary of Product Characteristics – Molita® (dipyridamole + aspirin) 200 mg/25 mg modified-release capsules, hard. Dr Reddy’s Laboratories (UK) Ltd. Accessed via www.medicines.org.uk 10/08/2019 [date of revision of the text March 2017]
  6. Blood S. Medication Considerations before surgery. The Pharmaceutical Journal. 2012; 288:179