Purine Nucleoside Phosphorylase Deficiency Medication

Replacement therapy with intravenous immunoglobulin in patients with primary immune deficiencies

Regarding replacement therapy with intravenous immunoglobulin (IVIG) in patients with primary immune deficiencies, the overall consensus among clinical immunologists is that a dose of IVIG at 400-600 mg/kg/mo or a dose that maintains trough serum IgG levels of more than 500 mg/dL is desirable.^{[26, 27]} Patients with meningoencephalitis (X-linked agammaglobulinemia) require higher doses (eg, 1 g/kg) and perhaps intrathecal therapy.

Preinfusion, or trough, serum IgG levels are measured every 3 months until a steady state is achieved and then every 6 months if the patient is stable. These levels may be helpful in adjusting the dose of IVIG to achieve adequate serum levels. For persons with high catabolism of infused IgG, more frequent infusions (eg, every 2-3 wk) of smaller doses may maintain the serum level in the reference range. The rate of IgG elimination may be increased during active infection; therefore, measuring serum IgG levels and adjusting to higher doses or shorter intervals may be required.

Precautions and adverse reactions to intravenous immunoglobulin therapy

The US Food and Drug Administration (FDA) advises against exceeding the recommended doses and infusion rates and suggest the use of minimal practical concentrations in patients at risk for renal failure (eg, those with preexisting renal insufficiency, diabetes, volume depletion, sepsis, paraproteinemia; those older than 65 y; and those using nephrotoxic drugs).

Initial treatment should be administered under the close supervision of experienced personnel. The risk of adverse reactions with initial treatments is high, especially in patients with infections and in those who form immune complexes. In patients with active infection, infusion rates may need to be reduced and the dose halved (ie, 200-300 mg/kg), with the remaining dose given the next day to achieve a full dose. Treatment should not be discontinued. After normal serum IgG levels are achieved, adverse reactions are uncommon unless patients have active infections.

With the new generation of IVIG products, adverse effects are reduced. Adverse effects include tachycardia, chest tightness, back pain, arthralgia, myalgia, hypertension or hypotension, headache, pruritus, rash, and low-grade fever. More serious reactions are dyspnea, nausea, vomiting, circulatory collapse, and loss of consciousness. Patients with profound immunodeficiency or active infections have reactions more severe than those of other patients.

The adverse reactions are thought to be related to the anticomplementary activity of IgG aggregates in the IVIG and the formation of immune complexes. The formation of oligomeric or polymeric IgG complexes that interact with Fc receptors and that trigger the release of inflammatory mediators is another cause. Most adverse reactions are rate related. Slowing the infusion rate or discontinuing therapy until symptoms subside may diminish the reaction. Pretreatment with ibuprofen (5-10 mg/kg every 6-8 h), acetaminophen (15 mg/kg/dose), diphenhydramine (1 mg/kg/dose), and/or hydrocortisone (6 mg/kg/dose, maximum 100 mg) 1 hour before the infusion may prevent adverse reactions. In some patients with a history of severe adverse effects, doses of analgesic and antihistamine may be repeated.

Acute renal failure is a rare but significant complication of IVIG treatment. Reports suggest that IVIG products that contain sucrose as a stabilizer are associated with an increased risk for this renal complication. Acute tubular necrosis, vacuolar degeneration, and osmotic nephrosis suggest osmotic injury to the proximal renal tubules. The infusion rate for sucrose-containing IVIG should not exceed 3 mg/kg/min based on sucrose content. Risk factors for this adverse reaction are preexisting renal insufficiency, diabetes mellitus, dehydration, age older than 65 years, sepsis, paraproteinemia, and concomitant use of nephrotoxic agents. For patients at increased risk, BUN and creatinine levels should be monitored before the start of treatment and before each infusion. If renal function deteriorates, the product should be discontinued.

IgE antibodies to immunoglobulin A (IgA) have been reported to cause severe transfusion reactions in patients with IgA deficiency. The literature has a few reports of true anaphylaxis in patients with selective IgA deficiency and common variable immunodeficiency (CVID) who developed IgE antibodies to IgA after treatment with Ig. In actual experience, however, this is rare. In addition, this is not a problem for patients with X-linked agammaglobulinemia (Bruton disease) or severe combined immunodeficiency (SCID). Caution should be exercised in patients with IgA deficiency (< 7 mg/dL) who need IVIG because of IgG-subclass deficiencies. IVIG preparations with low concentrations of contaminating IgA are advised (see Table 2).

Comparison of intravenous immunoglobulin products

For replacement therapy in patients with primary immune deficiency, all brands of IVIG are probably equivalent, although their viral inactivation processes (eg, solvent detergent vs pasteurization and liquid vs lyophilized) may differ (see Table 2). The choice may depend on the formulary, local availability, and/or cost. The dose, manufacturer, and lot number should be recorded for each infusion to review for adverse events or other consequences. Recording all adverse effects that occur during the infusion is crucial. Periodic monitoring of liver and renal function about 3-4 times yearly, is also recommended.

Table 2. Intravenous Immunoglobulin^{[28, 29, 30]} (Open Table in a new window)

Class Summary

Prophylactic treatment for P carinii pneumonia is TMP-SMZ. Administer IVIG therapy to provide functional antibodies.

Trimethoprim and sulfamethoxazole (SMZ-TMP, Bactrim, Septra, Cotrim)

Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid; for prophylaxis of P carinii pneumonia.

Fluconazole (Diflucan)

Synthetic PO antifungal (broad-spectrum bistriazole) that selectively inhibits fungal cytochrome P-450 and sterol C-14 alpha-demethylation, which prevents conversion of lanosterol to ergosterol, thereby disrupting cellular membranes. Has little affinity for mammalian cytochromes, which is believed to explain its low toxicity. Available as tablets for PO administration, as a powder for PO suspension, and as a sterile solution for IV use. Indicated for fungal prophylaxis during immunosuppression

Class Summary

The optimal combination of an ablative agent (ie, busulfan) with immunosuppressive agents (eg, antithymocyte globulin, cyclophosphamide) has not been systematically studied and should be the focus of future clinical trials. The risks of this preparative regimen are sterility, liver, heart and lung toxicity, and malignancy.

Busulfan (Myleran)

Potent cytotoxic drug; causes profound myelosuppression at recommended dose. As alkylating agent, mechanism of action of active metabolites may involve cross-linking of DNA, which may interfere with growth of normal and neoplastic cells.

Cyclophosphamide (Cytoxan, Neosar)

Chemically related to nitrogen mustards. As alkylating agent, mechanism of action of active metabolites may involve cross-linking of DNA, which may interfere with growth of normal and neoplastic cells.

Lymphocyte immune globulin (Atgam)

May modify T-cell function and might eliminate antigen-reactive T-lymphocytes in peripheral blood.

Class Summary

Cyclosporine and corticosteroids are administered to prevent acute GVHD.

Cyclosporine (Sandimmune, Neoral)

Cyclic polypeptide; suppresses some humoral immunity and more so cell-mediated immune reactions (eg, delayed hypersensitivity, allograft rejection, experimental allergic encephalomyelitis, GVHD) in many organs. Base dose on ideal body weight.

Methylprednisolone (Solu-Medrol)

Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.