Pentamidine

Pentamidine isetionate given by the intravenous route is an alternative for patients with severe Pneumocystis carinii (now renamed Pneumocystis jirovecii ) pneumonia unable to tolerate co-trimoxazole, or who have not responded to it. Pentamidine isetionate is a toxic drug and personnel handling the drug must be adequately protected. Nebulised pentamidine may be used for mild disease and for prophylaxis.Thin-walled air-containing cysts (pneumatoceles) and pneumathoraces are more common in patients receiving nebulised pentamidine as prophylaxis. Adverse effects, sometimes severe, are more common with pentamidine than co-trimoxazole.

Uses
Alternative treatment for severe Pneumocystis carinii pneumonia (PCP).

Administration
• IV infusion: 4 mg/kg every 24 hours for at least 14 days
  Dilute in 250 ml glucose 5%, given over 1–2 hours

In renal impairment:

CC (ml/min)	Dose (mg/kg)	Interval (h)
10–50	4	24
<10	4	24 for 7–10 days then on alternate days to complete a minimum of 14 doses

Adjuvant corticosteroid has been shown to improve survival.The steroid should be started at the same time as the pentamidine and should be withdrawn before the antibiotic treatment is complete. Oral prednisolone 50–80 mg daily or IV hydrocortisone 100 mg 6 hourly or IV dexamethasone 8 mg 6 hourly or IV methylprednisolone 1 g for 5 days, then dose reduced to complete 21 days of treatment.

How not to use pentamidine
Nebulised route not recommended in severe PCP (↓ PaO2)
Concurrent use of both co-trimoxazole and pentamidine is not of benefit and may increase the incidence of serious side-effects

Adverse effects
Acute renal failure (usually isolated serum creatinine)
Leucopenia, thrombocytopenia
Severe hypotension
Hypoglycaemia
Pancreatitis
Arrhythmias

Cautions
Blood disorders
Hypotension
Renal/hepatic impairment

Organ failure
Renal: reduce dose

Renal replacement therapy
No further dose modification is required during renal replacement therapy