The efficacy of trimethoprim-sulfamethoxazole for prophylaxis against PCP has been clearly demonstrated among pediatric cancer patients. The only reported randomized controlled trial of this drug combination for HIV-infected persons was a primary-prophylaxis study of 60 adult AIDS patients with Kaposi sarcoma, and compared the effect of no treatment with that of a regimen of 160 mg trimethoprim plus 800 mg sulfamethoxazole twice daily plus 5 mg leucovorin calcium once daily. Compared with untreated patients, those who received prophylaxis had fewer episodes of PCP and lived longer. Adverse reactions were common (50%) and included nausea, vomiting, pruritus, and rash, although these reactions also occurred commonly among patients who were not receiving trimethoprim-sulfamethoxazole.

Aerozalized pentamidine is also an acceptable means of prophylaxis. Primary prophylaxis of severely immunocompromised patients can be indicated where PCP has not yet been diagnosed. Secondary prophylaxis aims to prevent recurrent infections by PCP. For both forms of prophylaxis, an aerosolized formulation of pentamidine given by nebulizer once monthly in a dose of 300 mg is used. In primary prophylaxis, this reduces the long term likelihood of PCP by 70% when compared to no prophylaxis.

A recent review concludes that: “The use of intravenous pentamidine as PCP prophylaxis results in a breakthrough rate of 1.3%. TMP-SMZ is the first choice for PCP prophylaxis. However, when necessary, the use of intravenous pentamidine has an acceptably low failure rate, even in high-risk BMT patients. Other options should be considered for children less than 2 years of age.” It may sometimes be reasonable when TMP-SMS cannot be used and the child does not co-operate with inhalation.

Elayan, Mohammed M. et a, lMonthly Intravenous Pentamidine for the Prophylaxis of Pneumocystis Jiroveci Pneumonia in Adult Allogeneic Hematopoietic Stem Cell Transplant Recipients Biology of Blood and Marrow Transplantation , Volume 22 , Issue 3 , S163

Guidelines for Prophylaxis Against Pneumocystis carinii Pneumonia for Persons Infected with Human Immunodeficiency Virus MMWR 16, 1989 / 38(S-5);1-9current therapies and recommendations.   J Pediatr Oncol Nurs. 2011 May-Jun;28(3):179-84.

Crozier F. Pneumocystis carinii pneumonia prophylaxis:

While retrospective studies indicate that long-term steroid use increases the risk of PCP infection it is not known how these patients should be prophylaxed. The threshold for potential infection that warrants prophylaxis with its costs in side effects and expense is unknown, and the critical amount of immunosuppression necessary to increase risk for PCP is also unknown. Prophylaxis has been suggested for patients immunosuppressed owing to an underlying disease or immunosuppressive therapy. In some cancer centers, patients who receive corticosteroid therapy for longer than 4 weeks at a dose equivalent to 20 mg of prednisone per day are routinely are given PCP prophylaxis, as well as those in high-risk groups such as bone marrow transplant recipients and children with ALL.

In 2009, Kovacs and Masur summarized the first 100 years since identification of Pneumocystis. They concluded that in HIV-negative patients there is no reliable laboratory marker for risk of this infection, but that in these patients PCP is more likely to be an acute illness causing severe respiratory distress of rapid onset when compared with HIV-positive patients. That makes routine prophylaxis more reasonable. Their recommended approach is to use PCP prophylaxis in patients receiving at least 20 mg of prednisone per day for at least 1 month. They also note that steroid therapy can accelerate symptomatic and physiologic improvement and improve survival in patients with moderate or severe PCP. Since steroids are in themselves immunosupressive, management of corticosteroids in PCP-infected patients is quite complex.

Kovacs JA, Masur H. Evolving health effects of Pneumocystis: one hundred years of progress in diagnosis and treatment. JAMA. 2009;301:2578-2585.

Green H, Paul M, Vidal L, Leibovici L.Prophylaxis of Pneumocystis pneumonia in immunocompromised non-HIV-infected patients: systematic review and meta-analysis of randomized controlled trials. Mayo Clin Proc. 2007 Sep;82(9):1052-

Read the Layperson version here.

In this case, there appears to be no compellng reason to use Depocyt instead of the standard of care cytarabine. I do not consider it to be medically necessary.

Glantz, Michael J., Jaeckle, Kurt A., Chamberlain, Marc C., Phuphanich, Surasak, Recht, Lawrence, Swinnen, Lode J., Maria, Bernard, LaFollette, Susan, Schumann, G. Berry, Cole, Bernard F., Howell, Stephen B.
A Randomized Controlled Trial Comparing Intrathecal Sustained-release Cytarabine (DepoCyt) to Intrathecal Methotrexate in Patients with Neoplastic Meningitis from Solid Tumors
Clin Cancer Res 1999 5: 3394-3402

D. Mazhar, J. Stebbing, R. Lewis, M. Nelson, B. G. Gazzard, and M. Bower
The management of meningeal lymphoma in patients with HIV in the era of HAART: intrathecal depot cytarabine is effective and safe
Blood, April 15, 2006; 107(8): 3412 – 3414.

Depocyt, Prescribing information