Macitentan and Tadalafil - Indications, Side Effects, and Pharmacological Aspects

Overview

Macitentan and Tadalafil are two important therapeutic alternatives in the treatment of PAH (pulmonary arterial hypertension). Macitentan, an endothelin receptor antagonist, works by inhibiting endothelin's vasoconstrictive activities, which promotes vasodilation and reduces pulmonary vascular resistance. Tadalafil, a phosphodiesterase-5 (PDE-5) inhibitor, increases the effects of nitric oxide, causing pulmonary arterial smooth muscle cells to relax and blood flow to increase. The Food and Drug Administration approved Macitentan and Tadalafil on March 22, 2024.

Drug Group:

Macitentan and Tadalafil belong to the following medication groups:

• Macitentan: Endothelin receptor antagonists (ERA)

• Tadalafil: PDE-5 inhibitors

Available Doses and Dosage Forms:

Macitentan:

• Dosage Forms: Tablets

• Available Strengths: Typically available in 10 mg tablets

Tadalafil:

• Dosage Forms: Tablets

• Available Strengths: Common strengths include 2.5 mg, 5 mg, 10 mg, and 20 mg tablets

For Patients

What Is Pulmonary Arterial Hypertension?

Pulmonary arterial hypertension (PAH) is a dangerous disorder defined by high blood pressure in the pulmonary arteries, which deliver blood to the lungs. This causes thickening and constriction of the arterial walls, impeding blood flow and straining the right side of the heart.

PAH can cause symptoms including shortness of breath, exhaustion, chest discomfort, and dizziness, and if not addressed, it can progress to major problems like right heart failure and death. The diagnosis is based on a medical history, physical examinations, imaging studies, and blood testing.

The goal of treatment is to relieve symptoms and halt disease development with drugs, including vasodilators and prostacyclin analogs. PAH requires constant management and monitoring by healthcare experts to enhance results and quality of life.

How Do Macitentan and Tadalafil Work?

• Macitentan: It is an endothelin receptor antagonist. Endothelin is a chemical in the body that causes blood vessels to constrict, resulting in higher blood pressure. Macitentan acts by inhibiting the actions of endothelin on its receptors, namely endothelin type A (ETA) and type B (ETB). By inhibiting these receptors, Macitentan helps to relax the blood vessels in the lungs, lowering pulmonary vascular resistance and increasing blood flow. This eventually lowers blood pressure in the pulmonary arteries and improves PAH symptoms.

• Tadalafil: It is a phosphodiesterase-5 (PDE-5) inhibitor. PDE-5 is an enzyme that degrades cyclic guanosine monophosphate (cGMP), a signaling molecule that relaxes smooth muscle cells in blood arteries, particularly those in the lungs. Tadalafil inhibits PDE-5, which raises cGMP levels, causing smooth muscle cells in the pulmonary arteries to relax and vasodilate. This improves blood flow to the lungs and reduces pulmonary vascular resistance, reducing PAH symptoms and enhancing exercise capacity.

What Are the Things to Inform the Doctor Before Taking Macitentan and Tadalafil?

• Medical History: Give a detailed medical history, including past or present medical illnesses such as liver disease, renal disease, heart disease, or blood disorders.

• Medication History: List all prescriptions, over-the-counter pharmaceuticals, vitamins, supplements, and herbal items. This covers any alternative therapies for pulmonary arterial hypertension or related diseases.

• Allergies: Inform the doctor about allergies, including allergies to medicines, particularly Macitentan, Tadalafil, or other comparable drugs.

• Pregnancy and Nursing: If pregnant, intend to become pregnant, or are breastfeeding, talk to a physician about the risks and benefits of taking Macitentan with Tadalafil. These drugs may pose dangers to the fetus or breastfeeding baby.

• Alcohol and Tobacco Use: Tell the doctor if one drinks or smokes since these drugs may interact with Macitentan or Tadalafil and increase its negative effects.

• Other Health Concerns: Talk about any other health issues or lifestyle variables that may affect Macitentan and Tadalafil therapy, such as eating habits, exercise routines, or plans for surgery or dental work.

• Side Effects and Symptoms: Be aware of the potential side effects of Macitentan and Tadalafil, and notify the physician in the event of noticing any odd symptoms while taking these drugs.

How Are Macitentan and Tadalafil Administered?

1. Macitentan:

• Administration: Orally, with or without meals.

• Dosage: Usually taken once a day.

• Important: Follow the healthcare provider's dosing recommendations strictly, and only change or quit Macitentan after first visiting the doctor.

2. Tadalafil:

• Administration: Orally, with or without meals.

• Dosage: Usually taken once a day.

• Dosage for PAH: The recommended dosage for PAH is 40 mg (two 20 mg tablets) or 20 mg (one 20 mg tablet) once daily, depending on specific patient variables and tolerance.

• Important: Follow the healthcare provider's exact dose directions for the situation. It is critical to only crush, chew, or break the pills if directed to do so by the physician.

Dietary Instructions:

While taking Macitentan with Tadalafil, eat a well-balanced diet rich in fruits, vegetables, whole grains, lean proteins, and fats. Limit the consumption of foods high in saturated fat, cholesterol, and salt. To avoid fluid retention, which is a risk factor for pulmonary arterial hypertension, limit salt consumption. Drink plenty of water to keep hydrated, but avoid drinking too much, which might increase fluid retention. Discuss alcohol use with a physician because it may interact with Macitentan and Tadalafil or exacerbate their negative effects. Be careful that some foods and beverages, such as grapefruit and juice, may interact with Tadalafil.

Side Effects:

1. Macitentan:

• Common adverse effects include headaches, swelling in the ankles and legs (peripheral edema), nasal congestion, upper respiratory tract infections, and anemia.

• Less common but dangerous adverse effects include liver disorders, such as elevated liver enzymes or liver toxicity. Seek medical help if symptoms include yellowing of the skin or eyes (jaundice), dark urine, stomach discomfort, or unexplained exhaustion.

2. Tadalafil:

• Common side effects include headaches, indigestion, back pain, muscular pains, flushing, a stuffy or runny nose, and dizziness.

• Less frequent but dangerous side effects include visual changes or abrupt vision loss, hearing loss or ringing in the ears, chest discomfort, irregular heartbeat, and allergic responses, including rash, itching, or swelling of the face, tongue, or neck. If one seems to experience these symptoms, they should get medical attention immediately.

Missed Dose:

If a dose is missed, the patient must take it upon recall unless it is almost time for the next planned dose. In that instance, skip the missing dosage and resume the usual dosing schedule. Avoid taking additional doses to make up for the missing one.

Adherence to the suggested dose schedule is critical for ensuring pharmaceutical efficacy in controlling the illness. Consider utilizing a pill organizer or setting a reminder alert if it is missed regularly.

Talk to a physician if one has any concerns or questions regarding missing doses or how to manage the medicine schedule. They can provide individualized advice depending on the patient's treatment plan and medical requirements.

Storage:

Keep Macitentan and Tadalafil in their original containers at room temperature, away from heat and moisture. Keep them out of reach for youngsters and dogs. Do not store them in the bathroom or near the kitchen sink. Check the expiration date and dispose of any expired medications carefully. Ask a pharmacist or healthcare professional for advice on correct storage in case of doubt.

For Doctors:

Indication:

Macitentan and Tadalafil are drugs used to treat pulmonary arterial hypertension (PAH), which is defined as high blood pressure in the arteries that deliver blood to the lungs. These drugs relieve symptoms, postpone disease development, and enhance the quality of life in PAH patients by relaxing blood vessels in the lungs, lowering pulmonary vascular resistance, and boosting blood flow.

Contraindication:

• Hypersensitivity: Individuals who have a known allergy or allergic response to Macitentan, Tadalafil, or any of the inactive chemicals in the pharmaceutical formulations should avoid using these medications.

• Pregnancy: Macitentan and Tadalafil are not recommended during pregnancy because of the potential for fetal damage. Women with reproductive potential should utilize effective contraception while taking Macitentan and Tadalafil.

• Severe Liver Impairment: Macitentan is contraindicated in people with severe hepatic impairment (Child-Pugh Class C). Tadalafil should be taken with care by people with severe liver impairment.

• Nitrates: Tadalafil is contraindicated in individuals using any type of organic nitrate, either regularly or intermittently, due to the possibility of severe hypotension.

• Riociguat: Tadalafil is not recommended for individuals using Riociguat, a medicine used to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension, due to the risk of hypotension.

• Alpha Blockers: Tadalafil should be taken with caution by individuals using alpha-blockers, as the combination may cause symptomatic hypotension in some people.

What Are the Pharmacological Aspects of Macitentan and Tadalafil?

1. Mechanism of Action

• Macitentan: Macitentan is an endothelin receptor antagonist that inhibits the action of endothelin, a chemical that induces vasoconstriction and high blood pressure. By inhibiting endothelin receptors (particularly endothelin type A and type B receptors), Macitentan induces vasodilation, lowers pulmonary vascular resistance, and enhances blood flow in the pulmonary arteries.

• Tadalafil: Tadalafil is a phosphodiesterase-5 (PDE-5) inhibitor that raises cGMP levels in smooth muscle cells. Elevated cGMP levels relax smooth muscle cells in the pulmonary arteries, causing vasodilation, lower pulmonary vascular resistance, and better blood flow to the lungs.

2. Pharmacokinetics:

• Macitentan: Macitentan is well absorbed following oral treatment, reaching peak plasma concentrations after eight hours. Its lengthy half-life is between 16 and 48 hours, allowing for a once-daily dosage. Macitentan is extensively metabolized in the liver, largely by the cytochrome P450 enzyme CYP3A4, and its metabolites are excreted primarily through feces.

• Tadalafil: Tadalafil is readily absorbed following oral treatment, reaching peak plasma concentrations within two hours. It has a relatively long half-life of around 17.5 hours, enabling once-daily administration to treat pulmonary arterial hypertension (PAH). Tadalafil is largely processed by the cytochrome P450 enzyme CYP3A4 in the liver, with minor contributions from CYP3A5 and CYP2C9. Feces mostly remove their metabolites, with a small amount secreted in urine.

Clinical Efficacy:

• Clinical studies have shown that Macitentan and Tadalafil are effective in treating pulmonary arterial hypertension (PAH), enhancing exercise capacity, lowering symptoms, and delaying disease progression.

• Combination treatment with Macitentan and Tadalafil has been demonstrated to give additional advantages to some PAH patients when compared to either medicine alone.

Warnings and Precautions:

• Hypotension: Both drugs can lower blood pressure, causing symptoms like dizziness, lightheadedness, and fainting. Macitentan or Tadalafil should be administered with caution to individuals with low blood pressure or who are using antihypertensive drugs. Blood pressure should be checked frequently throughout therapy.

• Hepatic Impairment: Macitentan is contraindicated in people with severe hepatic impairment (Child-Pugh Class C). Tadalafil should be used with caution in individuals with mild to severe hepatic impairment. Periodic liver function tests should be performed when using Macitentan or Tadalafil.

• Pulmonary Edema: Macitentan has been linked to pulmonary edema in individuals with pulmonary veno-occlusive disease (PVOD). Therefore, it should be administered with caution to individuals with PVOD or pulmonary capillary hemangiomatosis.

• Priapism: Tadalafil has been linked to incidents of prolonged erection (priapism), which can result in irreversible penile injury if not addressed swiftly. Patients should seek emergency medical assistance if an erection lasts longer than four hours while using Tadalafil.

• Vision and Hearing Loss: Tadalafil has been linked to uncommon incidents of abrupt vision loss, reduced eyesight, sudden hearing loss, or ringing in the ears (tinnitus). Patients who experience these symptoms should stop taking Tadalafil and seek medical assistance.

• Drug Interactions: Macitentan and Tadalafil may interact with other drugs, such as strong inducers or inhibitors of cytochrome P450 enzymes. When providing Macitentan or Tadalafil with other medications that may impact their metabolism or raise the risk of unwanted effects, use caution.

• Pregnancy and Contraception: Macitentan and Tadalafil are not recommended during pregnancy owing to the potential for fetal damage. Women with reproductive potential should utilize effective contraception while taking Macitentan and Tadalafil.

• Alcohol: Patients should avoid drinking excessively while taking Macitentan or Tadalafil since it might increase adverse effects, including dizziness and hypotension.

Drug Interaction:

• CYP3A4 Inducers: The cytochrome P450 enzyme CYP3A4 is responsible for the primary metabolism of Macitentan. The concurrent use of powerful CYP3A4 inducers such as Rifampin, Phenytoin, Carbamazepine, and St. John's Wort may lower Macitentan plasma concentrations, lowering its efficacy. When used in conjunction with CYP3A4 inducers, Macitentan dosage may need to be adjusted.

• CYP3A4 Inhibitors: Strong CYP3A4 inhibitors such as Ketoconazole, Itraconazole, Clarithromycin, Ritonavir, and grapefruit juice may raise Macitentan and Tadalafil plasma concentrations, increasing the risk of side effects. When taking Macitentan or Tadalafil with powerful CYP3A4 inhibitors, dose modifications or alternate drugs may be required.

• Nitrates: Tadalafil is contraindicated in people using organic nitrates regularly or intermittently, owing to the risk of severe hypotension. Concurrent use of Tadalafil with nitrates or nitric oxide donors may increase the hypotensive effects of both medicines and is hence not advised.

• Riociguat: Tadalafil is contraindicated in individuals using Riociguat, a medicine used to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension since it increases the risk of hypotension. Concurrent usage of Tadalafil and Riociguat is not recommended.

Clinical Studies:

1. Macitentan:

• SERAPHIN Trial: This pivotal Phase III clinical trial evaluated the effectiveness and safety of Macitentan in PAH patients. The study found that Macitentan significantly decreased the risk of morbidity and death compared to placebo. Patients who received Macitentan had a decreased risk of disease progression, fewer hospitalizations for PAH-related comorbidities, and greater exercise capacity than those who received a placebo. Adverse effects ranged in intensity from mild to serious, with peripheral edema and headache being the most prevalent.

2. Tadalafil:

• PHIRST-1 and PHIRST-2 Studies: These Phase III clinical studies looked at the effectiveness and safety of Tadalafil in PAH patients. The trials found that Tadalafil considerably increased exercise capacity, as determined by the 6-minute walk distance, compared to placebo. Tadalafil also enhances quality of life while reducing PAH symptoms. Adverse effects were mostly mild to severe, with headaches, dyspepsia, and flushing being the most prevalent.

• Pulmonary Arterial Hypertension and Response to Tadalafil (PHIRST) Study Extension: This long-term extension research examined the safety and effectiveness of Tadalafil in PAH patients for 2.5 years. Tadalafil therapy resulted in persistent increases in exercise capacity, quality of life, and hemodynamics. Adverse events were similar to those reported in the first PHIRST studies, and no new safety issues were discovered.

Specific Considerations:

• Liver Function Monitoring: Perform regular liver function testing, especially in individuals with liver disease, and modify doses for hepatic impairment.

• Pregnancy Prevention: To avoid teratogenic consequences, women of reproductive potential should use effective contraception during and after therapy.

• Vision and Hearing Monitoring: Monitor for visual and hearing abnormalities, including abrupt loss, and discontinue Tadalafil if symptoms develop.

• Patient Education: Inform patients on correct pharmaceutical usage, such as dose, side effects, and the significance of adherence and reporting symptoms.

• Regular Follow-Up: Schedule follow-up appointments to check for treatment response and side effects.

• Individualized Treatment: Tailor treatment to the patient's features, comorbidities, and preferences, considering age, gender, renal and hepatic function, concomitant drugs, and treatment objectives.