Pentamidine

Question 1

Pentamidine

Answer 1

Primarily alternative to T/S for Pneumocystis pneumonia; was once an extremely common cause of severe pneumonia in HIV infected patients- becoming less common with effective antiretroviral therapy

Very toxic- extensive adverse effects

Route depends on indication- either IV or inhalation

Question 2

Pentamidine MOA

Answer 2

Appears to bind and disrupt the function of tRNA- resulting in inhibition of protein synthesis

Question 3

Pentamidine Spectrum

Answer 3

Like a parasite but technically a fungus:
P. jirovecii

Protozoa:
Trypanosoma
Leishmania

Question 4

Pentamidine (IV) Adverse Effects

Answer 4

CV
Hypotension can occur with rapid infusion of pentamidine- infuse at least over an hour
Cases of QT prolongation with ventricular arrhythmia have been reported

Metabolic
Toxic to pancreas- dysglycemias in 25% of patient; may initially manifest as hypoglycemia; pentamidine induced pancreatic injury caused release of insulin from islet cells
Continuing injury can cause decrease in pancreatic function- hypoinsulinemia and hyperglycemia
Continued use may lead to irreversible damage, leaving patients with diabetes
Other manifestations of pancreatitis may occur

Renal
Nephrotoxicity common
Generally reversible upon discontinuation
Electrolyte disturbances, including hypoK and hypoCal may occur

Respiratory
Inhalation form may induce bronchoconstriction (especially in asthma)
Pretreatment with inhaled bronchodilator may attenuate effects

Question 5

Pentamidine Important Facts

Answer 5

In trials for Pneumocystis pneumonia, about equal efficacy compared to T/S; only about half of patients could tolerate full course of IV without discontinuing or decreasing dose

Careful monitoring (ECG, metabolic panel) and supportive care (electrolyte replacement, glucose, or insulin) as necessary 
Dosage adjustment in renal insufficiency recommended 

Once monthly inhaled form has reasonable efficacy as second line agent for prophylaxis against Pneumocystis pneumonia
Unlike T/S prophylaxis, extra pulmonary Pneumocystis infections have been reported while on inhaled form; also does not protect against Toxoplasma disease or bacterial pneumonia like T/S

Question 6

Pentamidine Good For

Answer 6

IV as an alternative for treatment severe Pneumocystis pneumonia

Inhaled as alternative for prophylaxis against P. pneumonia

IV alternative for treatment of leishmaniasis and trypanosomiasis