Clinically Important Drug Interactions in Hypertension:

More presentations from Naina Mohamed Pakkir Maideen

Hypertension (High blood pressure) is a long term medical condition in which the force of the blood against artery walls is high.

©     Blood pressure is determined by Heart Rate (HR), Stroke Volume (SV) and Peripheral Vascular Resistance.

©    Common Antihypertensives include…

Ø Angiotensin converting enzyme inhibitors (ACEIs) (Captopril, Lisinopril, perindopril, etc)

Ø Angiotensin receptor blockers (ARBs) (Losartan, Valsartan, Telmisartan, etc)

Ø Direct Renin Inhibitors (DRIs) (Aliskiren)

Ø Calcium channel blockers (CCBs) (Nifedipine, Amlodipine, Nicardipine, etc)

Ø Diuretics (Frusemide, Thiazides, Spiranolactone, etc)

Ø Adrenergic Beta Blockers (Atenolol, Bisoprolol, Cervedilol, etc),

Ø Adrenergic Alpha Blockers (Prazosin, Terazosin, etc)

Ø Vasodilators (Nitrates, Hydralazine, Minoxidil, etc)

©    The patients with Hypertension may take one or more Antihypertensives along with other prescription and over-the-counter (OTC) medications, herbal products, vitamins and/or foods which may result adverse drug interactions.

©    The Antihypertensives which should not be combined (Contraindications) with other drugs include…

Ø ACEIs or ARBs + Aliskiren

Ø Felodipine or Nisoldipine + Ketoconazole or Itraconazole

Ø Verapamil + Dofetilide

Ø Verapamil or Diltiazem + Colchicine

Ø Diltiazem + Cisapride

Ø Nitrates + PDE 5 Inhibitors (Sildenafil, Tadalafil, Vardenafil, Avanafil)

Ø Nitrates + Riociguat

©    The combinations (Antihypertensives + Other drugs) which increase the risk of Hyperkalemia include…

Ø ACEIs or ARBs + Aliskiren

Ø ACEIs or ARBs + Potassium Sparing Diuretics

Ø ACEIs or ARBs + Trimethoprim

Ø ACEIs + Potassium Supplements

Ø ACEIs + Cyclosporine

Ø Potassium sparing diuretics  + Arginine

Ø Potassium sparing diuretics  + Trimethoprim

Ø Potassium sparing diuretics + Potassium supplements

©    The combinations (Antihypertensives + Other drugs) which increase the risk of Cardiotoxicity include…

Ø Felodipine or Nisoldipine  + Ketoconazole or Itraconazole

Ø Verapamil + Dofetilide

Ø Diltiazem + Cisapride

Ø Verapamil or Diltiazem + Macrolides

©    The combinations (Antihypertensives + Other drugs) which increase the risk of Hypotension include…

Ø ACEIs or ARBs + Aliskiren

Ø Nitrates + PDE 5 Inhibitors (Sildenafil, Tadalafil, Vardenafil, Avanafil)

Ø Nitrates + Riociguat

Ø ACEIs + ARBs

Ø Dihydropyridines + CYP3A4 Inhibitors

Ø Verapamil or Diltiazem & Beta Blockers

Ø Beta blockers + Antiarrhythmics  (Amiodarone, Dronedarone)

Ø Beta blockers + CCBs (Verapamil, Diltiazem)

Ø Alpha 1 blockers + PDE 5 Inhibitors (Sildenafil, Tadalafil)

©    Minimizing the risk for drug interactions should be a goal in drug therapy to reduce the occurrence of significant morbidity and mortality.

©    The patients with hypertension should bring a list of all of the drugs they are taking including prescription drugs, over-the-counter drugs, and any supplements, herbal or otherwise, during their visit to the doctor or pharmacist.

Drug Interactions of Antihypertensives (Part 13):

Drug Interactions of Organic Nitrates:

More presentations from Naina Mohamed Pakkir Maideen

© Organic nitrates  include Isosorbide dinitrate, Isosorbide mononitrate, Nitroglycerin (GTN), Erythrityl tetranitrate and Pentaerythritol tetranitrate.

©   Organic nitrates are commonly used to treat angina pectoris, myocardial infarction, and congestive heart failure.

©   Nitroglycerine may be useful to lower blood pressure in acute hypertensive emergencies resulting from a pheochromocytoma, renal artery stenosis, aortic dissection, etc. Nitrodilators may also be used during surgery to control arterial pressure within desired limits.

©   Mechanism of Action of Organic nitrates in Angina pectoris:

©   Mechanism of action of Organic nitrates in Heart Failure:

©   Organic nitrates can interact with drugs such as PDE 5 Inhibitors (Sildenafil, Tadalafil, Vardenafil, Avanafil) and Riociguat.

©   Concomitant use of Organic nitrates and PDE 5 Inhibitors such as Sildenafil, Tadalafil, Vardenafil and Avanafil is Contraindicated.

©   Coadministration of Riociguat with Organic nitrates is contraindicated due to an increased risk of hypotension.

©   If possible, concomitant use of Nitroglycerin (GTN) and Alteplase should be avoided.

©   Careful monitoring of PTT and Heparin dose adjustment is recommended, when heparin and Nitroglycerin (GTN) are coadministered.

©   The patients with hypertension should bring a list of all of the drugs they are taking including prescription drugs, over the counter (OTC) drugs, and any supplements, herbal or otherwise, during their visit to the doctor or pharmacist.

Drug Interactions of Antihypertensives (Part 12):

Drug Interactions of Arterial Vasodilators:

More presentations from Naina Mohamed Pakkir Maideen

©   Arterial Vasodilators include Hydralazine and Minoxidil.

©   Arterial Vasodilators are commonly used to treat Systemic and Pulmonary hypertension, heart failure and angina. 

©   Hydralazine can interact moderately with drugs such as Beta blockers (Propranolol, Oxprenolol, Metoprolol), Indomethacin, Ma Huang (Ephedra) and Yohimbine.

©   The risk of adverse effects (Bradycardia, Fatigue, and Bronchospasm) of Beta blockers is elevated by the concurrent use of Hydralazine and Beta blockers. Switch to a sustained release beta blocker, if concurrent therapy of Hydralazine and Beta blockers is required.

©   Concomitant use of Hydralazine and Indomethacin warrants monitoring of blood pressure.

©   Due to ephedrine content of Ma Huang, concomitant use of Ma huang is not advised in patients using antihypertensives.

©   Use of Ma huang is contraindicated in patients who are ephedrine or pseudoephedrine sensitive, and those with renal failure or pheochromocytoma.

©   Avoid concomitant use of Hydralazine or Minoxidil and yohimbine.

©   Maintenance of consistent dosing of Hydralazine is recommended with relation to meals.

Drug Interactions of Antihypertensives (Part 11):

Drug Interactions of Alpha 1 Blockers:

More presentations from Naina Mohamed Pakkir Maideen

©   Alpha 1 blockers include Irreversible α₁ blockers (Phenoxybenzamine), Reversible α₁ blockers (Imidazoline derivative - Phentolamine (α₁, α₂ blocker)) and α₁ Selective blockers (Quinazoline Derivative – Prazosin, Terazosin and Doxazosin).

©   Alpha 1 blockers are used to treat various illnesses including Benign Prostatic Hyperplasia (BPH), Hypertension, etc.

©   Alpha 1 blockers can interact majorly with drugs such as Phosphodiesterase 5 inhibitors (Sildenafil, Tadalafil) and Asenapine.

©    Moderate interaction of Alpha 1 blockers includes Beta blockers and Yohimbine (Alpha 2 blocker).

©   Use caution when PDE 5 inhibitors for erectile dysfunction (ED) and Alpha 1 blockers are coadministered.

©   Monitor blood pressure and reduce the dosage of the Alpha 1 blockers when they are coadministered with Asenapine.

©   Monitor the patient closely for hypotension while using Alpha 1 blocker and Beta blocker concomitantly.

©   Avoid concomitant use of yohimbine and alpha-1 adrenergic blockers.

©   The patients with hypertension should bring a list of all medications they are taking including prescription drugs, over the counter (OTC) drugs and any supplements during their visit to the doctor or pharmacist.

Drug Interactions of Antihypertensives (Part 10):

Drug Interactions of Beta Blockers:

More presentations from Naina Mohamed Pakkir Maideen

©   Beta blockers include Non selective (β₁,β₂ ) blockers (Proponolol, Timolol, Nadolol, Pindolol, Labetalol and Carvedilol) and Selective β₁ blockers (Atenolol, Esmolol, Metoprolol, Bisoprolol, Betaxolol and Nebivolol).

©   Beta blockers are used to treat various illnesses including Hypertension, Angina  pectoris (But contraindicated in Prinzmetal's angina), Cardiac arrhythmias, Congestive heart failure, Essential tremor, Glaucoma, Migraine prophylaxis, Mitral valve prolapse, Myocardial infarction, Phaeochromocytoma, etc.

©   Beta blockers can interact majorly with drugs such as Antiarrhythmics (Amiodarone, Dronedarone), CCBs (Verapamil, Diltiazem), Beta 2 agonists, Clonidine, Lacosamide, Crizotinib, Rivastigmine and Fenoldopam.

©   Moderate interaction of Beta blockers includes Antidiabetic agents, CCBs (Amlodipine, Nifedipine, etc), Digitalis glycosides, NSAIDs, Alpha blockers, Phenothiazines and St.John’s wort.

©   Concomitant use of Beta blockers and Antiarrhythmics (Amiodarone, Dronedarone) warrants the monitoring of patients for signs of bradycardia or heart block.

©   Careful monitoring of cardiac function and blood pressure is required in patients taking Beta blockers and CCBs (Verapamil, Diltiazem).

©   Beta blockers are usually not recommended in asthmatic or COPD patients treated with Beta 2 agonists.

©   Monitor heart rate of patients taking Betablockers and Clonidine together.

©   If concurrent therapy of Beta blockers and Lacosamide is required, obtain ECG prior to treatment and following dose titration.

©   Monitor blood pressure and heart rate regularly, if coadministration of Beta blockers and Crizotinib is required.

©   Avoid concomitant use of Fenoldopam with beta adrenergic blockers.

©   Closely monitor for hypoglycemia with concurrent use of Beta blockers and Antidiabetics.

©   If concurrent therapy of Beta blockers and CCBs (Amlodipine, Nifedipine, etc) is required, monitor cardiac function carefully especially in patients predisposed to heart failure.

©   Monitor heart rate and PR interval, if Beta blockers and Digitalis glycosides are coadministered.

©   Concomitant use of Beta blockers and NSAIDs warrants the monitoring of patient's blood pressure.

©   Monitor the patient closely for hypotension, when Beta blockers and Alpha 1 blockers are coadministered.

©   Concomitant use of St. John's Wort and Beta adrenergic blockers is not recommended.

©   The patients with hypertension should bring a list of all of the drugs they are taking including prescription drugs, over the counter (OTC) drugs, and any supplements, herbal or otherwise, during their visit to the doctor or pharmacist.