Oral penicillin desensitisation protocol for adults

Ensure that penicillin desensitisation is appropriate for the patient (see Patient appropriateness for antimicrobial desensitisation) before performing oral penicillin desensitisation. Key requirements for antimicrobial desensitisation programs are listed in Key requirements for antimicrobial desensitisation programs.

A rapid oral amoxicillin or phenoxymethylpenicillin desensitisation protocol is shown in Rapid oral amoxicillin or phenoxymethylpenicillin desensitisation protocol for adults. When the drug required for treatment is amoxicillin or ampicillin, use amoxicillin to perform desensitisation. When the drug required for treatment is phenoxymethylpenicillin or benzylpenicillin, use phenoxymethylpenicillin to perform desensitisation.

Oral desensitisation with amoxicillin or phenoxymethylpenicillin can be used even if subsequent therapy will be with parenteral amoxicillin, ampicillin or benzylpenicillin, and is recommended because it is considered safer than intravenous desensitisation.

Table 1. Rapid oral amoxicillin or phenoxymethylpenicillin desensitisation protocol for adults
Castells 2019
Step (at 15-minute intervals)		Amoxicillin or phenoxymethylpenicillin suspension [NB1] [NB2]	Volume	Dose	Cumulative dose
Use Solution C [NB3]
1		0.5 mg/mL	0.1 mL	0.05 mg	0.05 mg
2		0.5 mg/mL	0.2 mL	0.1 mg	0.15 mg
3		0.5 mg/mL	0.4 mL	0.2 mg	0.35 mg
4		0.5 mg/mL	0.8 mL	0.4 mg	0.75 mg
5		0.5 mg/mL	1.6 mL	0.8 mg	1.55 mg
6		0.5 mg/mL	3.2 mL	1.6 mg	3.15 mg
7		0.5 mg/mL	6.4 mL	3.2 mg	6.35 mg
Use Solution B [NB3]
8		5 mg/mL	1.2 mL	6 mg	12.35 mg
9		5 mg/mL	2.4 mL	12 mg	24.35 mg
10		5 mg/mL	4.8 mL	24 mg	48.35 mg
Use Solution A [NB3]
11		50 mg/mL	1 mL	50 mg	98.35 mg
12		50 mg/mL	2 mL	100 mg	198.35 mg
13		50 mg/mL	4 mL	200 mg	398.35 mg
14		50 mg/mL	8 mL	400 mg	798.35 mg
15	Observe for 30 minutes; if no reaction occurs, administer: if amoxicillin was used for desensitisation, amoxicillin 1 g orally or intravenously, or ampicillin 1 g intravenously if phenoxymethylpenicillin was used for desensitisation, phenoxymethylpenicillin 500 mg orally or benzylpenicillin 1.2 g intravenously. After completing desensitisation, consider the desensitisation protocol as the first dose and start therapy at the standard dose and frequency required for the indication.
Note: NB1: Use amoxicillin to perform desensitisation when the drug required for treatment is amoxicillin or ampicillin. Use phenoxymethylpenicillin to perform desensitisation when the drug required for treatment is phenoxymethylpenicillin or benzylpenicillin. NB2: To make Solution A (50 mg/mL suspension), reconstitute the 250 mg/5 mL proprietary product with water for irrigation as specified on the bottle and shake well. Label the bottle as 50 mg/mL ‘Solution A’. To make Solution B (5 mg/mL suspension), take 10 mL of the 50 mg/mL (Solution A) and dilute to 100 mL with water for irrigation and shake well. Label the bottle as 5 mg/mL ‘Solution B’. To make Solution C (0.5 mg/mL suspension), take 10 mL of the 5 mg/mL (Solution B) and dilute to 100 mL with water for irrigation and shake well. Label the bottle as 0.5 mg/mL ‘Solution C’. NB3: Solutions should be stored in amber glass bottles, kept in the fridge, and shaken well before use. The solutions should be discarded 24 hours after preparation.