Continuing Education Activity
Fosinopril is classified as an angiotensin-converting enzyme inhibitor and has been available for nearly three decades. Fosinopril has some key features that make it different from enalapril and captopril; 1) it has a long half-life 2) it is hydrophilic, and 3) it is not broken down by the liver. Fosinopril is a competitive inhibitor of angiotensin-converting enzyme (ACE) and prevents the conversion of angiotensin I to angiotensin II, which is a potent vasoconstrictor. This activity covers fosinopril, including mechanism of action, pharmacology, adverse event profiles, eligible patient populations, monitoring, and highlights the role of the interprofessional team in the management of hypertension with fosinopril.
- Summarize the mechanism of action of fosinopril.
- Identify the various indications for initiating fosinopril therapy.
- Review the adverse event profile of fosinopril.
- Explain the importance of collaboration and communication among interprofessional team members to improve outcomes and treatment efficacy for patients receiving treatment with fosinopril.
Fosinopril is most often prescribed for a patient suffering from hypertension (<140/90 mmHg for noncomplicated patients and <130/80 mmHg for patients with either diabetes or chronic kidney disease). Fosinopril is an angiotensin-converting enzyme (ACE) inhibitor that aims to decrease systemic blood pressure in hypertensive patients. Other ACE inhibitors approved in the US are captopril, enalapril, lisinopril, benazepril, quinapril, ramipril, moexipril, and trandolapril.
Fosinopril is also prescribed as an adjunctive treatment of heart failure along with conventional therapy that includes diuretics with or without digitalis. Once-daily fosinopril treatment has shown to improve HF signs and symptoms and reduce the frequency of discontinuations or hospitalizations for worsening HF. In a fosinopril Efficacy/Safety Trial (FEST) Study Group, fosinopril has shown to improve exercise tolerance and attenuate clinical deterioration in patients with heart failure. Also, in the Fosinopril Acute Myocardial Infarction Study (FAMIS), early treatment with fosinopril has shown to benefit patients with acute myocardial infarction in addition to a prevention of left ventricular (LV) remodeling.
Fosinopril also works as a preventative therapy for patients with diabetic nephropathy. In a randomized diabetic nephropathy patient, fosinopril combined treatment with losartan resulted in reduced 24-hour urine, protein excretion, serum creatinine, and BUN.
Off-label use of fosinopril also includes the treatment of HIV-associated nephropathy (HIVAN).
Mechanism of Action
Fosinopril is an ester prodrug that hydrolyzes in the liver to fosinoprilat, the active metabolite form. Fosinoprilat then uses competitive inhibition to bind to ACE resulting in decreased formation of angiotensin II, reduced aldosterone concentrations, and diminished systemic vasoconstriction. By interacting with the components of the renin-angiotensin-aldosterone system (RAAS), fosinopril can reduce the tendency of vasoconstriction and promote sodium excretion. It helps in heart failure by protecting the myocardium from the angiotensin II remodeling effects.
Fosinopril received official approval for use in 1991 and is available for administration in 10, 20, or 40 mg oral tablets. It is traditional to prescribe the drug at a low dose and increase the dosage as needed while evaluating the patient’s response and tolerance. The maximum dose is typically 80 mg for the average hypertensive person. In patients with sodium or water depletion or renal failure, the initial dosing is reduced to 5 mg.
It’s not uncommon to co-administer hydrochlorothiazide with fosinopril to regulate fluid volume and counteract high blood pressure.
A few common symptoms reported with fosinopril include fatigue, dizziness, gastrointestinal disturbances, dry cough, and a skin rash. Long term usage of fosinopril can produce a dry cough due to the inhibition of ACE and the resulting accumulation of bradykinin. A less common side effect of which to be aware is angioedema. Other rarely reported adverse reactions are an elevation in serum aminotransferase concentrations and acute liver damage. Less than two percent of patients using fosinopril have reported increased serum aminotransferase levels without explanation. Since acute liver damage is an extremely rare reaction, only a handful of clinical reports have been documented and analyzed. Unfortunately, the few reports are insufficient to determine a consistent mechanism of injury, so the path of liver damage remains unknown in these patients. The metabolite reaction in the liver is proposed to cause the idiosyncratic adverse effect and remains under investigation. Other ACE inhibitors that have shown similar liver damage are enalapril, lisinopril, and lisinopril.
In cases of hepatic failure, it is crucial to avoid prescribing any ACE inhibitor. Patients experiencing the adverse effect of acute liver injury from fosinopril should refrain from using other ACE inhibitors to prevent further damage.
Also, fosinopril is contraindicated during pregnancy due to its ability to cross the placenta. As a result, it may increase the risk of fetal malformations and cause congenital disabilities or death to the developing fetus. If the patient reports pregnancy at any time during treatment, fosinopril therapy should stop immediately. In general, all ACE inhibitors should be avoided when treating hypertension in pregnancy.
In patients with diabetes, fosinopril should not be co-administered with aliskiren, as aliskiren may enhance the hypotensive, hyperkaliemia, and nephrotoxic effects of fosinopril.
One needs to be careful while using fosinopril with other drugs due to drug-drug interaction.
- With potassium (K+) sparing diuretics: Fosinopril may cause hyperkalemia due to the attenuation of potassium loss caused by thiazide diuretics.
- With lithium: Fosinopril causes serious lithium drug interaction. It may slow the elimination of lithium form the body, resulting in increased lithium levels.
- With antacids: Antacids may alter the absorption of fosinopril, resulting in reduced serum levels. It can further reduce the urinary excretion of fosinoprilat.
- With Non-steroidal anti-inflammatory agents: in elderly patients, co-administration of fosinopril may result in deterioration of renal function, possibly resulting in acute renal failure.
While on fosinopril, the patient requires monitoring for hypotension, potassium levels, renal function, and angioedema. To decrease the possibility of hypotension as an adverse effect among ACE inhibitors, the recommendation is to initially prescribe fosinopril at a low dose. During weeks 2 to 3 of usage, clinicians should note serum creatine and potassium levels as well as blood pressure to gauge the patient's tolerance. For instance, a patient with a history of hyperkalemia or a high potassium diet should have close monitoring to avoid exacerbating any preexisting conditions.
The incidence of angioedema occurring as an adverse effect is 0.1 to 0.7% due to vasodilation and plasma extravasation. If patients have a history of ACE inhibitor-induced angioedema, they should avoid using fosinopril or any other agent within that class.
If the patient is experiencing toxicity due to fosinopril, they will require general supportive care and should discontinue fosinopril immediately. The following case study describes a situation in which a patient suffered from the adverse effects of fosinopril.
The first documented case of a person experiencing uncommon adverse reactions due to fosinopril was a 61-year-old man who reported symptoms beginning during weeks 2 through 12 of treatment. The patient reported no prior hepatobiliary disease and consuming 3 to 4 alcoholic beverages daily. During the course of treatment with 20 mg fosinopril daily, he was also taking 50 mg of metoprolol twice a day and 5 mg of diazepam daily. After just three weeks of using fosinopril, the patient presented with asthenia, jaundice, and pruritis. Once admitted to the hospital, all medications were stopped, and treatment initiated. To treat the pruritis and cholestasis, he received ursodiol, colestipol, and hydroxyzine. Further examination also revealed him to have an elevated concentration of bilirubin, serum aminotransferase enzymes, and alkaline phosphatase. However, other levels, such as immunoglobulins and eosinophilia, were reportedly within normal limits. During hospitalization, the patient faced complications such as renal failure, which required dialysis, duodenal ulcer bleeding, and septicemia.
Upon evaluation, the patient tested negative for hepatitis A, B, and C in addition to other autoantibody tests. Furthermore, the patient showed no signs of biliary obstruction or gallstones from an abdominal ultrasound or tomography imaging. Also, there were no other contributions to intrahepatic cholestasis. Any other medications were determined to be improbable causes of the acute liver injury with which he presented. A liver biopsy showed positive results for cholestasis as well as bile duct destruction.
The patient was hospitalized for two months but continued to experience symptoms for up to 18 months after the incident. He reported having jaundice for four months, pruritis for six months, and anicteric cholestasis for 18 months.
The overall recovery period lasted from 6 to 18 months, and the severity rating was 4+. The risk of developing this acute liver injury due to fosinopril was categorized as a likelihood score of D. Other ACE inhibitors have shown similar risks for acute liver damage.
Enhancing Healthcare Team Outcomes
Even though fosinopril is a relatively safe and common means to treat hypertension, it is essential to monitor the drug and report any adverse effects under an interprofessional healthcare team. Physicians that tend to prescribe this class of ACE inhibitors include but are not limited to primary care physicians, internal medicine specialists, and cardiologists. Before using fosinopril, the patient should be aware of all the possible side effects and receive instructions to avoid high potassium diets. To ensure the patient is maximizing their benefits from fosinopril, physicians should schedule regular follow-ups and document the patient's response. A pharmacist should have involvement at the outset of therapy, verifying appropriate dosing and dose titration, checking for potential interactions, and counseling the patient on possible adverse effects. Nursing will follow up with the patient and also monitor therapy progress and answer patient questions, alerting the prescriber to any concerns. With these interprofessional strategies, fosinopril can achieve better outcomes with fewer adverse effects. [Level 5]