2.4. Antiprotozoals, antipneumocystosis, and antitoxoplasmosis drugs

· pentamidine, pyrimethamine, calcium folinate (cytotoxic)

Pentamidine

In an effort to address the increasing problem of toxoplasmosis and infection with Pneumocystis carinii in immunosuppressed patients, the 1997 MEDL incorporated a new section, which included these agents. This section included pentamidine isetionate, pyrimethamine, and sulfamethoxazole plus trimethoprim. Pentamidine isetionate was previously included in the list as an antitrypanosomal drug (at 200 mg strength). The new strength included, 300 mg, is available from several manufacturers. However, no replies were received for this drug in either the mid-2000 survey or the expressions of interest. Two presentations exist, powder for injection and nebulizer. The 200 mg presentation is offered only by RhPoulenc, and is available through WHO for trypanosomiasis programmes.

Use in HIV/AIDS: Prophylaxis of Pneumocystis carinii pneumonia (PCP), treatment of PCP in patients unable to tolerate first-line treatment.

Notes in 11^th Model list: Specific expertise, diagnostic precision, individualization of dosage or special equipment required for proper use.

- powder for injection, 200 mg (isetionate) in vial. MEDL.
- powder for injection, 300 mg (isetionate) in vial. MEDL. Reported shelf-life: 18 to 60 months.

Pyrimethamine

Pyrimethamine is an essential component of treatment regimes against Toxoplasma gondii. Pyrimethamine is available both as a generic from international suppliers and as a branded product (Glaxo Wellcome). While generic pyrimethamine tablets are available at low cost, they are used in combination with calcium folinate (to reduce its toxicity) and sulfadiazine or clindamycin, and therefore adequate access to these drugs must also be secured.

Use in HIV/AIDS: Treatment of toxoplasmic encephalitis and other manifestations of active toxoplasmosis, treatment of isosporidosis.

- tablet, 25 mg. MEDL.

Calcium folinate (cytotoxic drug)

Calcium folinate is included in the MEDL as a cytotoxic drug. However, it is an essential drug for the treatment and prophylaxis of toxoplasmosis, where it is used to reduce the toxicity of pyrimethamine. It is considered an expensive drug, and its price is a critical factor in the total drug cost of toxoplasmosis management. Originally a product of Wyeth Lederle, calcium folinate in tablet form is available as a generic. While indicative prices varied widely, low cost sources were found.

Use in HIV/AIDS: To decrease the toxicity of pyrimethamine and other inhibitors of folic acid.

Notes in 11^th Model list: Specific expertise, diagnostic precision, individualization of dosage or special equipment required for proper use (these precautions apply mainly in the context of chemotherapy with 5-fluorouracil, not for its use in HIV/AIDS).

- tablet, 15 mg. MEDL. Reported shelf-life: 24 to 36 months.

Table 7. Sources and prices of antipneumocystosis and antitoxoplasmosis drugs

Table 8. Drug costs associated with the treatment of toxoplasmosis