Switching between oral prednisolone and IV hydrocortisone

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Switching between oral prednisolone and intravenous (IV) hydrocortisone requires care due to the risk of adrenal insufficiency or adrenal crisis.

Reason for switching

The National Patient Safety Alert (NPSA) on steroid emergency cards highlights that missing doses of corticosteroids when on long-term and/or high dose therapy can risk adrenal insufficiency or even adrenal crisis, which is a medical emergency.

In some cases, prescribers may need to switch from oral prednisolone to intravenous (IV) hydrocortisone. For example when people:

  • have severe vomiting, persistent diarrhoea or other severe illness
  • have gastrointestinal obstructions that reduce the absorption of medicines given orally
  • are not allowed to have any form of food, drink or medicine by mouth

These situations may be temporary and require IV hydrocortisone to replace the oral prednisolone and avoid the risk of adrenal crisis.

Always confirm why the switch from oral prednisolone to IV hydrocortisone is required and refer to the steroid sick day rules. A switch to IV hydrocortisone may not always be needed.

Considerations for switching

Consider the following points before switching between formulations.

Formulations available

The available UK formulations are:

  • oral prednisolone – tablet, soluble tablet, gastro-resistant tablet, and oral solution
  • IV hydrocortisone – solution for injection, powder for solution for injection, and powder with solvent for solution for injection

Glucocorticoid activity

Hydrocortisone has a 1 to 1 ratio for glucocorticoid (anti-inflammatory) and mineralocorticoid (water retention) properties.

Prednisolone has a 4 to 0.8 ratio for glucocorticoid (anti-inflammatory) and mineralocorticoid (water retention) properties.

The relatively high mineralocorticoid activity of hydrocortisone makes it unsuitable for disease suppression on a long-term basis.

Switch individuals from IV hydrocortisone to an oral corticosteroid as soon as possible. This may mean restarting their oral prednisolone at a higher dose than they were previously on and weaning back to baseline.

Hydrocortisone potency

When comparing anti-inflammatory potency, 5mg of oral prednisolone is equipotent to 20mg of oral hydrocortisone.

Oral hydrocortisone has a bioavailability of near 100%.

Based on this, 5mg of oral prednisolone is similar in anti-inflammatory potency to 20mg of IV hydrocortisone.

Hydrocortisone effect

When comparing duration of action (e.g. anti-inflammatory effect), prednisolone has a longer duration of effect (18 to 36 hours) than hydrocortisone (8 to 12 hours).

Based on this, the equipotent dose of hydrocortisone may have to be repeated more frequently to maintain the same level of anti-inflammatory effect.

Clinical considerations

Local policies for IV hydrocortisone administration may differ. Please refer to your local policy in the first instance.

For IV hydrocortisone

The following points should be considered when switching to IV hydrocortisone:

  • injection doses can be repeated at intervals of 2, 4 or 6 hours
  • injections are usually administered over 1 to 10 minutes
  • infusions are usually administered over 20 to 30 minutes or as a continuous infusion

For planned operations

Refer to the guidelines for the management of glucocorticoids during the peri-operative period for patients with adrenal insufficiency.

Converting doses

There is no specific guidance on how to switch from oral prednisolone to IV hydrocortisone. Based on the glucocorticoid potency and bioavailability, it should be possible to switch from one formulation to the other without a delay in dosing.

The risk of adrenal insufficiency and adrenal crisis outweighs the risk of additive side effects from prednisolone and hydrocortisone exposure.

Monitoring after the switch

There is no guidance on what should be monitored after switching from oral prednisolone to IV hydrocortisone.

Update history

  1. Removal of worked example following user feedback. Text added to highlight difference in duration of effect.
  1. Published

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