Issues for surgery
For pulmonary arterial hypertension (PAH) – loss of pulmonary arterial pressure control and worsening of symptoms if omitted.
For benign prostatic hyperplasia (BPH) – risk of acute urinary retention if omitted.
For digital ulcers (associated with systemic sclerosis) [unlicensed indication] – risk of development of ulcers to fingers or toes if omitted.
Risk of hypotension if continued.
Risk of QT-interval prolongation if continued (see Interactions with common anaesthetic agents and Interactions with other common medicines used in the perioperative period).
Advice in the perioperative period
Elective surgery
Continue.
Except:
- For erectile dysfunction (ED) – advise patient not to take the day prior to and the day of procedure.
Patients with PAH
Planning for elective surgery should involve a discussion with the patient's specialist centre.
Emergency surgery
Follow the advice as for elective surgery. If dose(s) taken due to indication, or prior to admission, monitor BP.
Patients with PAH
A discussion with the patient’s specialist centre should be considered if there is time prior to emergency surgery.
Post-operative advice
For PAH/BPH/digital ulcers
Restart post-operatively once enteral intake resumes and ensure to correct any volume depletion. If a long nil by mouth (NBM) period is anticipated, or there are concerns with enteral absorption, advice should be sought from a specialist, especially for PAH.
Monitor BP (see Further information).
For ED
Hold whilst inpatient.
Interactions with common anaesthetic agents
Hypotension
PDE5 inhibitors can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics.
QT-interval prolongation
See also Interactions with other common medicines used in the perioperative period.
Sildenafil has some risk for prolonging the QT-interval. Co-administration of sildenafil with medicines known to prolong the QT-interval must be based on a careful assessment of the potential risks and benefits for each patient since the risk of torsade de pointes may increase.
Anaesthetic agents that may be used in the perioperative period that are known to, or predicted to, prolong the QT-interval include:
- desflurane, isoflurane, sevoflurane – avoid
- thiopental*
*monitor ECG if concurrent use unavoidable; if risk factors for QT-prolongation are also present (increasing age, female sex, cardiac disease, and some metabolic disturbances e.g. hypokalaemia) use greater caution
Interactions with other common medicines used in the perioperative period
Hypotension
PDE5 inhibitors can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine.
QT-interval prolongation
See also Interactions with common anaesthetic agents.
Sildenafil has some risk for prolonging the QT-interval. Co-administration of sildenafil with medicines known to prolong the QT-interval must be based on a careful assessment of the potential risks and benefits for each patient since the risk of torsade de pointes may increase.
Medicines that may be used in the perioperative period that are known to, or predicted to, prolong the QT-interval include:
- ciprofloxacin* (see also below)
- clarithromycin* (see also below)
- domperidone – avoid
- droperidol – avoid
- erythromycin (particularly intravenous)* (see also below)
- granisetron – avoid if risk factors
- haloperidol – avoid
- loperamide (increased risk with high doses)*
- ondansetron – avoid
- prochlorperazine (theoretical risk)*
*monitor ECG with concurrent use if risk factors for QT-interval prolongation also present (increasing age, female sex, cardiac disease, and some metabolic disturbances e.g. hypokalaemia).
Hypokalaemia
Corticosteroids may cause hypokalaemia, increasing risk of torsade de pointes, which may be additive to effects of sildenafil – monitor serum potassium closely with prolonged use.
Antimicrobials
Macrolides
Clarithromycin and erythromycin are predicted to increase the exposure to PDE5 inhibitors due to inhibition of CYP3A4.
Ciprofloxacin
Ciprofloxacin moderately increases the exposure to sildenafil. For patients taking sildenafil for PAH, monitor for an increase in adverse effects (such as headache, flushing, hypotension).
Whilst single surgical prophylactic doses should not pose a problem, consult product literature for recommendations regarding dose adjustments and monitor closely should continued post-operative treatment be required.
Further information
Hypotension
Due to their vasodilatory effects, PDE5 inhibitors can cause hypotension. Where sildenafil is being used for PAH, it should be avoided if systolic blood pressure (SBP) falls below 90 mmHg (diastolic blood pressure < 50 mmHg) and caution should be exercised where there is intravascular volume depletion.
Treatment discontinuation
It is recommended that abrupt discontinuation of PDE5 inhibitors for PAH should be avoided due to possible clinical deterioration. There is no published data on how to manage omission of more than one dose of PDE5 inhibitors and where omission cannot be avoided, advice should be sought from a specialist before re-introducing the medication.
References
Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com (Accessed on 20th September 2023)
Baxter K, Preston CL (eds), Stockley’s Drug interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com (Accessed on 20th September 2023
Summary of Product Characteristics – Viagra® (sildenafil) 100mg film-coated tablets. Upjohn UK Limited. Accessed via www.medicines.org.uk 20th September 2023 [date of revision of the text November 2022]
Sildenafil Citrate. In:Brayfield A (Ed), Martindale: The Complete Drug Reference. London: The Royal Pharmaceutical Society of Great Britain. http://www.medicinescomplete.com (Accessed on 20th September 2023)
Narenchania S, Torbic H, Tonelli A. Treatment Discontinuation or Interruption in Pulmonary Hypertension. Journal of Cardiovascular Pharmacology and Therapeutics, 2020; 25(2): 131 – 141