Alveolar targeting of aerosol pentamidine. Toward a rational delivery system

Delivering drugs to the lungs: The history of repurposing in the treatment of respiratory diseases

The repurposing of drug delivery by the pulmonary route has been applied to treatment and prophylaxis of an increasingly wide range of respiratory diseases. Repurposing has been most successful for the delivery of inhaled bronchodilators and corticosteroids in patients with asthma and chronic obstructive pulmonary disease (COPD). Repurposing utilizes the advantages that the pulmonary route offers in terms of more targeted delivery to the site of action, the use of smaller doses, and a lower incidence of side-effects. Success has been more variable for other drugs and treatment indications. Pulmonary delivery is now well established for delivery of inhaled antibiotics in cystic fibrosis (CF), and in the treatment of pulmonary arterial hypertension (PAH). Other inhaled treatments such as those for idiopathic pulmonary fibrosis (IPF), lung transplant rejection or tuberculosis may also become routine. Repurposing has progressed in parallel with the development of new drugs, inhaler devices and formulations.

CD4 lymphocyte count as predictor of drug expenditure in a cohort of anti-HIV seropositive haemophiliacs

The CD4 lymphocyte counts of 76 haemophilic patients who acquired HIV infection from unsterilised clotting factor concentrate were measured and the cost of all drugs used to treat each patient calculated. A rapid rise in drug costs was seen as patients' CD4 counts approached 0.2×109/L, the level at which zidovudine treatment and prophylaxis against Pneumocystis carinii are started. The relationship between decline in CD4 counts and cost of drugs was found to be linear. The authors conclude that it is possible to use CD4 counts to predict future drug costs.

Delivery strategies for antiparasitics

Optimisation of drug carrier systems and drug delivery strategies that take into account the peculiarities of individual infectious agents and diseases are key elements of modern drug development. In the following, different aspects of a rational design for antiparasitic drug formulation will be reviewed, covering delivery systems such as nano- and microparticles, liposomes, emulsions and microemulsions, cochleates and bioadhesive macromolecules. Functional properties for each carrier system will be discussed as well as their therapeutic efficacy for parasitic diseases, including leishmaniasis, human African trypanosomiasis, human cryptosporidiosis, malaria and schistosomiasis. Critical issues for the application of drug carrier systems will be discussed, focusing on biopharmaceutical and pathophysiological parameters such as routes of application, improvement of body distribution and targeting intracellularly persisting pathogens.

Aerosolized pentamidine prophylaxis for Pneumocystis carinii pneumonia after allogeneic marrow transplantation

Pneumocystis carinii pneumonia (PCP) poses a serious risk to allogeneic bone marrow transplant (BMT) patients, who are often intolerant of trimethoprim-sulfamethoxazole (TMP-SMX), the traditional first-line prophylactic agents. There are limited published data supporting the use of aerosolized pentamidine (AP) prophylaxis in the BMT population. We assessed the effectiveness of AP in BMT recipients by reviewing the experience at our center. We divided our review into four time periods from January 1990 to March 2000, during which approximately 700 BMTs were performed. The first period includes patients receiving AP treatments from January 1990 to July 1997 (baseline), the second from August 1997 to July 1998 (pre-outbreak), the third from August 1998 to October 1999 (outbreak), and the fourth from November 1999 to March 2000 (post-outbreak). At our center, TMP-SMX is the first-line agent for PCP prophylaxis, which is routinely continued for at least one year, or for the duration of enhanced immunosuppression. During the baseline period, 505 BMTs were performed and 192 patients (38%) received AP for part of their time at risk. Six patients (3%) experienced toxicities requiring discontinuation of AP. Three cases of PCP were diagnosed over 1114 patient-months of treatment in the baseline period. During the last 42 months of the baseline period, 2/154 patients receiving AP and 2 of an estimated 293 patients receiving exclusively oral prophylaxis developed breakthrough PCP (p = 0.61). During the outbreak period, 9 of 180 patients receiving AP developed PCP compared to none in the group receiving exclusively oral prophylaxis. Either changes in our AP protocol during the pre-outbreak period or pentamidine resistance may have led to this failure of prophylaxis. There were no further cases during the 5-month post-outbreak period. Our observed overall breakthrough rate was 12 cases out of 439 patients (2.7%). Our study shows that AP is an effective and well-tolerated second-line agent in preventing PCP post BMT and we recommend its continued use in this regard. However, it should be administered using a well-studied protocol, and only when TMP-SMX is not tolerated.

Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition

PURPOSE

To determine whether deposition pattern is related to in vitro measurements of droplet size, plume geometry, and spray pattern between two different nasal spray pumps believed to have different performance characteristics.

METHODS

Ten healthy volunteers inhaled radiolabeled saline from two different spray pumps (pump A and pump B). Deposition pattern was quantified from lateral views of the nose by gamma scintigraphy, expressed as the ratio of anterior to posterior (I:O) and superior to inferior (U:L) deposition. Droplet size was determined by Malvern Mastersizer S. Spray patterns were determined at 2.5 and 5 cm from the tip of the spray nozzle. Two-dimensional images of the emitted plume were captured by high-speed still photography.

RESULTS

There were no significant differences in I:O or U:L ratios for pump A compared to pump B, indicating no significant differences in deposition pattern. The volume diameters, Dv10 and Dv50, were not statistically different for pump A compared to pump B. There was a significant difference in Dv90 between pump A and pump B, (86.9 +/- 5.8 microm and 77.4 +/- 2.4 microm. respectively; P < 0.001). The ratio of the longest to shortest diameter for the spray pattern with pump A was 1.26 +/- 0.06 at 2.5 cm and 1.44 +/- 0.08 at 5 cm. The ratio for pump B was 1.13 +/- 0.03 at 2.5 cm and 1.19 +/- 0.05 at 5 cm. Ratios at both heights were statistically different for pump A compared to pump B (P < 0.00002 and P < 0.000001, respectively) Plume geometry analysis indicated statistical differences in both the width (17.0 +/- 0.97 vs. 18.5 +/- 0.56 cm, respectively: p<0.001) and the maximum length of the plumes (46.0 +/- 1.83 vs. 53.1 +/- 4.88 cm, respectively; p < .002). The differences in velocity of the plume and spray angle between the two pumps were not statistically different. CONCLUSIONS. Certain in vitro tests detected performance differences between the two pumps. However, these differences did not translate into different deposition patterns in vivo.

Amphotericin B disposition after aerosol inhalation in lung transplant recipients

BACKGROUND

Bronchopulmonary fungal infections continue to be a major cause of morbidity and mortality in lung transplant recipients, and amphotericin B remains the drug of choice for prophylaxis of most fungal infections. Unfortunately, intravenous amphotericin B has numerous serious adverse effects; thus, nebulized amphotericin B could decrease the incidence of adverse effects seen with the intravenous formulation and provide high local concentrations in the lung tissue. We performed a prospective pilot study to characterize the bronchoalveolar lavage (BAL), lung tissue, and plasma concentrations of amphotericin B following inhalation administration to lung transplant recipients.

METHODS

Amphotericin B 30 mg was administered by nebulizer prior to a routine bronchoscopy. Amphotericin B concentrations in BAL samples from the upper and lower lobes, transbronchial biopsies, and plasma (obtained by drawing a blood sample 30 min after the amphotericin B inhalation) were analyzed by HPLC.

RESULTS

Eight patients were enrolled in the study (mean age 50.0 +/- 16.1 y; number of years posttransplant 3.0 +/- 1.9; type of transplant 5 double-lung, 3 single-lung). The mean amphotericin B concentration in the upper and lower lobe BAL samples were 0.68 +/- 0.36 and 0.50 +/- 0.31 microgram/mL, respectively. Amphotericin B concentrations, detected in only 2 of 5 biopsy samples, were 0.118 and 0.03 microgram/g. Amphotericin B was detected in the plasma of only 1 patient (0.19 mg/L).

CONCLUSIONS

This pilot study demonstrated that detectable concentrations of amphotericin B can be attained in both the upper and lower BAL samples following aerosol administration. However, the frequency of the dose and duration of treatment still need to be determined in a larger study.

Delivery systems for penetration enhancement of peptide and protein drugs: design considerations

This paper discusses the challenges to be met in designing delivery systems that maximize the absorption of peptide and protein drugs from the gastrointestinal and respiratory tracts. The ideal delivery system for either route of administration is one that will release its contents only at a favorable region of absorption, where the delivery system attaches by virtue of specific interaction with surface determinants unique to that region and where the delivery system travels at a rate independent of the transitory constraints inherent of the route of administration. Such a delivery system, which is as yet unavailable, will benefit not only peptide and protein drugs, but other poorly absorbed drugs.

Influence of temperature on the emitted dose of an oral metered dose inhaler

The performance of metered dose inhalers is critical for the efficient delivery of drugs to the intended site of deposition in the respiratory tract. The temperature at which metered dose inhaler products are used by patients may influence the physicochemical characteristics of the emitted dose. Product performance characteristics of a metered dose inhaler containing beclomethasone dipropionate and oleic acid in a blend of chlorofluorocarbon propellants, Freon-11 and Freon-12, were determined by cascade impaction analysis and dose delivery through the valve after the metering chamber was loaded and actuated at 4 degrees C, 23 degrees C, and 40 degrees C. The dose delivered from the valve was not affected by the temperature at which the metering chamber was loaded and actuated. The mass median aerodynamic particle size of the emitted aerosol decreased and the percentage respirable fraction increased as the temperature was increased. The geometric standard deviation of the particle size distribution was not significantly affected by the temperature at which the metering chamber was loaded and actuated. The temperature at which a metered dose inhaler is used by a patient may influence the amount of drug that is potentially respirable; therefore, the dose expected to be delivered and the corresponding therapeutic effect may also be affected.

The physiologic effects of inhaled amphotericin B

Our institution used an experimental protocol for the use of inhaled amphotericin B as a prophylactic measure to prevent fungal disease in severely immunocompromised patients. We did a prospective study of the physiologic effects of amphotericin B administration. We looked specifically at oxygen saturation levels, peak flow values, and symptoms of patients given amphotericin B. We collected data on a series of 18 patients and of 132 amphotericin B administrations. Four (22%) of the patients stopped treatments because of nausea and vomiting which were believed to be due to the inhaled amphotericin B. For the remaining patients, no treatment was stopped because of symptoms or physiologic changes caused by amphotericin B, although there were 9 instances of clinically significant bronchospasm as defined by a drop in peak flow of 20% or more, 9 clinically relevant increases in cough, and 3 clinically relevant increases in dyspnea. Forty-eight percent of the clinically relevant changes occurred in patient 8. Another 16% occurred in asthmatic subjects who were significantly more likely (p = 0.03) to experience a 20% or more drop in peak flow than were patients without asthma. The physiologic profile of the response to inhaled amphotericin B is acceptable.

Regional deposition and regional ventilation during inhalation of pentamidine

In most patients, the deposition of aerosolized pentamidine (AP) is less in the apex of the lung relative to the base. As the apex of the lung is relatively less ventilated than the base, it is possible that reduced regional ventilation may explain the inhomogeneity in regional drug deposition. The purpose of this study was to measure the relationship between regional deposition of AP and regional ventilation, and the influence of particle size and airway caliber on this relationship. Ten subjects with HIV infection who were receiving prophylaxis with AP were recruited. Using krypton (81mKr), we measured regional ventilation during treatment with AP, labeled with 99mTc. Two nebulizers were used (Respirgard II and Fisoneb) that produced particles of different size. In addition, patients were studied with and without a bronchodilator because changes in airway geometry can affect sites of particle deposition. There was no significant correlation between regional ventilation and regional particle deposition (r = 0.00, linear regression). Particle deposition in the upper lobes relative to the lower lobes was less than would be predicted by regional ventilation, by a ratio of 0.84 +/- 0.03 (mean +/- SE). Using two-way analysis of variance (ANOVA), the upper to lower zone deposition pattern was not affected by either nebulizer or by the use of albuterol. The Fisoneb had significantly more central deposition relative to the jet nebulizer (mean +/- SE, skC/P: Fisoneb 1.3 +/- 0.1, Respirgard 1.1 +/- 0.1, p = 0.005, two-way ANOVA). The use of a bronchodilator did not significantly affect the central/peripheral deposition pattern. We conclude that differences in deposition between upper and lower lung regions are not accounted for simply by differences in regional ventilation in patients undergoing prophylaxis with AP. In assessing the cause of regional inhomogeneities of pharmaceutical aerosol deposition (and in devising strategies to achieve more uniform distribution), regional ventilation should be measured directly rather than be inferred from the deposition pattern of the aerosol.

Lung deposition from four nebulizers

The total and regional deposition of aerosol has been compared using four nebulizers; the Pari Boy 37.80, Pari IS-2, RespirGard II and Penta-Sonic. The aerosol was radiolabelled with [99Tcm]DTPA, administered to ten healthy subjects and the distributions monitored by gamma scintigraphy. Median lung aerosol depositions expressed as percentages of the doses initially loaded into the nebulizers were: Pari IS-2 19%, Pari Boy 37.80 13%, RespirGard II 9% and Penta-Sonic 2%. The ratios of the peripheral to central lung deposition, however, were greater with the RespirGard II and Penta-Sonic nebulizers. The choice of the most appropriate nebulizer depends on the pharmaceutical being administered, since aerosol must be delivered to the required site in sufficient quantity, whilst minimizing the incidence of local or systemic side-effects.

Involvement of tachykinins in pentamidine-induced airway constriction and microvascular leakage in the guinea pig

We investigated the effects of aerosolized pentamidine isethionate on airway constriction and microvascular leakage in the guinea pig, and the role of tachykinins in these abnormalities. The bronchoconstrictor response to pentamidine was determined in anesthetized, tracheotomized and mechanically ventilated guinea pigs by exposing them to increasing concentrations of aerosolized pentamidine (5 to 30 mg/ml; 60 breaths). Respiratory system resistance was measured by the occlusion method. Airway microvascular permeability was evaluated by measuring the Evans blue dye concentration in the trachea and main bronchi. Aerosolized pentamidine caused a concentration-related increase in respiratory system resistance that was prevented by pretreatment with 50 mg/kg capsaicin given subcutaneously 2 wk before pentamidine and was significantly reduced by pretreatment with 1 mg/kg morphine given intravenously. Pretreatment with 10(-4) M aerosolized phosphoramidon (90 breaths) significantly enhanced the bronchoconstrictor response to pentamidine. Aerosolized pentamidine (50 mg/ml; 90 breaths) increased airway microvascular permeability, as the Evans blue dye concentration was 72.6 +/- 3.7 ng/mg tissue in guinea pigs aerosolized with pentamidine versus 34.2 +/- 3.5 ng/mg tissue in the controls. Capsaicin pretreatment inhibited the increase in microvascular leakage induced by pentamidine. Pretreatment with 5 mg/ml aerosolized albuterol (90 breaths) prevented the bronchoconstrictor response to pentamidine but failed to prevent the pentamidine-induced increase in microvascular permeability. Atropine did not modify the bronchoconstrictor response to pentamidine. These results indicate that in the guinea pig, pentamidine isethionate induces bronchoconstriction and airway microvascular leakage, which are mediated by tachykinins released from sensory nerves. Albuterol, which is used in humans to prevent bronchoconstriction, does not seem able to prevent airway edema.

Measurement of particle and mass distribution of pentamidine aerosol by ultrasonic and air jet nebulizers

The use of appropriate nebulizers is a major precondition for a successful treatment and prevention of Pneumocystis carinii pneumonia with pentamidine aerosol. The apparatus should supply a sufficient amount of pentamidine with adequate particle size. Using Fisons ultrasonic nebulizer FISO Neb, model FZV 40 BAMKI, De Vilbiss ultrasonic nebulizer, Porta-Sonic, model 8500 GB, and the Marquest Medical Products jet nebulizer Respirgard II, two pentamidine concentrations (300 mg/6 ml and 60 mg/6 ml) were compared by measuring nebulized pentamidine mass distribution and particle size distribution under in vitro conditions by means of a laser light-scattering particle sizer of the type Malvern Master sizer. It was found that there were significant differences among nebulizers. Mass distribution experiments with air flow 6 l/min showed that using FISO Neb the quantity of nebulized pentamidine was 201.4 mg and 36.7 mg, whereas using Porta-Sonic the values found decreased to 85.2 mg and 23.6 mg. Using Respirgard II the values were 80.0 mg and 10.64 mg. The measured total duration times of nebulization were 6 - 8.5 min, 12 min and 25 min for the nebulizers FISO Neb, Porta-Sonic and Respirgard II. A decomposition of pentamidine during nebulization in the case of ultrasonic nebulizers doesn't take place. The measured mass median diameters (MMD) were 5.6 - 6.9 mum, 1.96 - 3.04 mum and 1.9 - 2.5 mum for the nebulizers FISO Neb, Porta-Sonic and Respirgard II. Using 300 mg pentamidine the nebulized amounts of pentamidine containing particles sizes less than or equal to 2 mum predominately available for alveolar deposition were with values of about 43 mg markedly higher for Respirgard II and Porta-Sonic than the measured 10.5 mg for FISO Neb.

Progression of HIV disease in a haemophilic cohort followed for 11 years and the effect of treatment

OBJECTIVE

To describe the progression of HIV disease in a haemophilic cohort and to show the influence of treatment.

DESIGN

11 year longitudinal clinical and laboratory study.

SETTING

A haemophilia centre.

PATIENTS

111 patients infected with HIV during October 1979 to July 1985.

MAIN OUTCOME MEASURES

Symptoms of HIV infection, AIDs, and death.

INTERVENTIONS

26 asymptomatic patients started taking zidovudine or placebo (1000 mg/day) during November 1988 to February 1990; 10 patients with CD4+ counts of 0.2 x 10(9)/l started zidovudine 500 mg/day during January to November 1990. 35 patients used pentamidine for primary or secondary prophylaxis.

RESULTS

At 11 years from seroconversion the estimated rate of progression to AIDS was 42% (95% confidence interval 27% to 57%); to symptoms 85% (75% to 95%); and to death 41% (25% to 57%). Progression to AIDS was significantly faster in patients aged 25 and over than in those aged less than 25 (relative risk 5.0 (2.4 to 10.4); p less than 0.00001) and in those with previous cytomegalovirus infection than in those not infected (relative risk 3.0 (1.4 to 6.8); p = 0.006). 16 of 27 (59%) patients with p24 antigenaemia developed AIDS compared with 17 of 84 (20%) patients without p24 antigen (p less than 0.001). The risk of progression to AIDS before 30 November 1988 in patients with CD4+ counts less than or equal to 0.2 x 10(9)/l was higher than after November 1988 (relative risk 1.9 (0.85 to 4.43); p = 0.1). For 1989 and 1990 the observed cumulative numbers of AIDS cases (among 81 patients with sufficient CD4+ counts) were 22 and 25 compared with 29 and 37 predicted from the rate of fall of CD4+ counts up to the end of 1988 (p = 0.03).

CONCLUSION

Treatment seems to be reducing the progression of HIV disease in this haemophilic cohort.