Paromomycin Sulfate/Gentamicin

Dear Sir: We read with interest the clinical trial reported by Sosa and others1 in which topical paromomycin/WR 279,369/gentamicin was compared with paromomycin alone for the treatment of New World cutaneous leishmaniasis (NWCL) caused by Leishmania panamensis. The authors concluded that the combination product may provide greater clinical benefit than paromomycin alone. The authors stated that paromomycin plus methylbenzethonium chloride (MBCL) ointment has not been evaluated alone against L. panamensis. However, Krause and others2 published a non-randomized study of patients in Ecuador with L. panamensis NWCL, with paromomycin sulphate plus MBCL ointment administrated twice a day for 10 days or once a day for 20 days, compared with untreated patients. Cure rates were 85%, 85%, and 9%, respectively. Moreover Armijos and others3 in 2004 performed a randomized controlled trial in Ecuador in patients with Leishmania guyanensis, Leishmania braziliensis, and Leishmania panamensis NWCL, in which topical paromomycin plus MBCL ointment was compared with topical paromomycin sulphate plus urea, both twice a day for 30 days, compared with meglumine antimoniate for 10 days. The cure rates at 3 months were 79%, 70%, 92%, respectively. The cure rates in these two studies were similar to those seen by Sosa and others1 with combination therapy (86%). Thus, good cure rates for L. panamensis NWCL can be obtained when paromomycin ointment is combined with other agents. However, this was not shown for Leishmania major old world cutaneous leishmaniasis, where no significant difference in efficacy between paromomycin with or without gentamicin was seen.4 Currently a phase 3, randomized, double-blind trial to determine if WR 279,396 is superior to paromomycin alone for L. panamensis NWCL in Panama is ongoing.5 Taking the previous data into account, probably a third therapeutic regimen based on paromomycin 15% plus MBCL 12% should have been included. Finally, we would like to mention that Sosa and others1 assert that their entry criteria of < 10 cutaneous lesions and no evidence of systemic dissemination conferred a very low risk for future mucosal infection. However, other authors consider local therapy for NWCL caused by L. braziliensis and L. panamensis unsuitable because of the potential risk of metastasis or secondary mucosal spread, and local therapy is recommended only for patients with ≤ 4–5 lesions.6,7 New clinical trials comparing local treatments for L. panamensis NWCL with long follow-up periods to determine the risk of mucosal dissemination are necessary.

This study evaluated the pharmacokinetics of topical creams containing 15% paromomycin (“paromomycin alone”) and 15% paromomycin plus 0.5% gentamicin (WR 279,396) in patients with cutaneous leishmaniasis. The investigational creams were applied topically to all lesions once daily for 20 days. Plasma samples were analyzed for simultaneous quantitation of paromomycin and gentamicin isomers and total gentamicin. Pharmacokinetic parameters for gentamicin could not be calculated because detectable levels were rarely evident. After one application, the paromomycin area under the concentration-time curve from 0 to 24 h (AUC 0–24 ) was 2,180 ± 2,621 ng · h/ml (mean ± standard deviation [SD]) for the paromomycin-alone group and 975.6 ± 1,078 ng · h/ml for the WR 279,396 group. After 20 days of application, the paromomycin AUC 0–24 and maximum concentration of drug ( Cmax ) were 5 to 6 times greater than those on day 1 for both treatment groups. For the paromomycin-alone group, the AUC 0–24 was 8,575 ± 7,268 ng · h/ml and the Cmax was 1,000 ± 750 ng/ml, compared with 6,037 ± 3,956 ng · h/ml and 660 ± 486 ng/ml for the WR 279,396 group, respectively. Possibly due to large intersubject variability, no differences ( P ≥ 0.05) in the AUC 0–24 or Cmax were noted between treatment or between sites on day 1 or 20. The percentage of dose absorbed on day 20 was 12.0% ± 6.26% and 9.68% ± 6.05% for paromomycin alone and WR 279,396, respectively. Paromomycin concentrations in plasma after 20 days of application were 5 to 9% of those after intramuscular administration of 15 mg/kg of body weight/day to adults for the systemic treatment of visceral leishmaniasis. Effective topical treatment of cutaneous leishmaniasis appears to be possible with limited paromomycin and gentamicin systemic absorption, thus avoiding drug accumulation and toxicity. (The work described here has been registered at ClinicalTrials.gov under registration no. NCT01032382 and NCT01083576.)