Canterbury DHB

Pneumocystis Pneumonia

Pneumocystis jiroveci is an opportunistic pathogen whose natural habitat is the lung. See UpToDate website for general information about pneumocystis.

Clinical Features

Symptoms are usually of slow onset over several days or longer (up to eight weeks) and include:

• shortness of breath (initially on exertion)
• fever
• chills
• non-productive cough.

Signs include:

• tachypnoea
• tachycardia
• cyanosis
• hypoxia, sometimes only initially apparent after exercise.
• increased LDH
• bilateral diffuse infiltrate on CXR.

Investigations/Diagnosis

• Arterial blood gases/SaO₂ – hypoxemia and desaturation (>5%) on exercise are common.
• CXR – diffuse interstitial infiltration (CXR may be normal in up to 5% of cases).
• Induced sputum, using nebulised hypertonic saline. Stain for pneumocystis but request legionella, mycobacterial, and viral culture if negative.
• Bronchoalveolar Lavage (BAL) is frequently necessary to make the diagnosis. Consult with infectious diseases.

Discuss with Microbiologist/Microbiology Registrar and inform them that these samples are coming as only a limited number of laboratory staff can process them for pneumocystis.

Treatment

Begin treatment for presumed pneumocystis with trimethoprim + sulfamethoxazole after one induced sputum specimen has been taken. The bronchoscopy is likely to remain positive up to 24 hours after commencing treatment.

Dosing is based on trimethoprim 15 - 20 mg/kg/day in 4 divided doses PO/IV for 14 days. Usually begin with IV infusion.

Note: 1 ampoule = 1 tablet = 80 mg trimethoprim and 400 mg sulfamethoxazole.

For example, for an 80 kg person, give 1200-1600 mg trimethoprim, i.e. 15-20 vials/tablets per day (7200 mg – 9600 mg per day).

For IV, dilute in a smaller volume than recommended in the datasheet. See the Notes on Injectable Drugs Handbook:

• 1-3 ampoules in 250 mL 5% dextrose
• 3-6 ampoules in 500 mL 5% dextrose
• ≥ 6 ampoules in 1 litre 5% dextrose

Infuse over 1 hour. The IV dose is usually given every 6 hours.

Trimethoprim + sulfamethoxazole is very well absorbed. Patients can be changed to an equivalent oral dose when they begin to improve, or if there are significant issues with IV access.

Oral dosing: round to the nearest tablet (80 mg trimethoprim).

Trimethoprim + sulfamethoxazole inhibits folic acid synthesis. Consider giving folinic acid 15 mg ONCE daily in patients with low platelets and neutrophils.

See the Medsafe website for further details of high dose trimethoprim + sulfamethoxazole treatment, since this drug may have serious dose limiting side effects.

The indication for treatment with prednisone is PaO < 65 mmHg.

Prednisone dose is:

• 40 mg BD for 5 days,
• 40 mg ONCE daily for 5 days, and
• 20 mg ONCE daily for 5-10 days depending on severity.

Note: If a definite diagnosis has not been made and the patient is not responding to treatment within 48 hours, consult infectious diseases (bronchoscopy is usually indicated in this situation).

If a rash occurs or if the patient has an allergy to trimethoprim + sulfamethoxazole, consider pentamidine infusion 4 mg/kg per day in 50-250 mL 5% dextrose or 0.9% saline and run over 2 hours. Pentamidine may have serious side effects (hypotension, hypoglycaemia, arrhythmias, pancreatitis, and others) and these need to be reviewed before commencing this drug.

Another option is Clindamycin plus primaquine.

Clindamycin can be dosed either orally 450 mg four times a day or IV 600 mg four times a day.

Primaquine is only oral 30 mg once daily. It should not be used in patients with G6PD deficiency as they may develop a haemolytic anaemia. G6PD deficiency is most common in those of African, African American, Mediterranean, Indian, and Asian origin.

Topic Code: 5026