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EXECUTIVE SUMMARY OF THE 2020 CLINICAL PRACTICE GUIDELINES FOR THE MANAGEMENT OF HYPERTENSION IN THE PHILIPPINES

I. DIAGNOSIS OF HYPERTENSION

• Measurement of Blood Pressure (BP)

  • Diagnosis based on repeated, reproducible measurements of elevated BP.

  • Not based on symptoms reported by the patient.

  • Often asymptomatic until end-organ damage is imminent or has occurred; referred to as the "Silent Killer."

• Blood Pressure Classification for Adult Filipinos

  • Normal BP: < 120/80 mmHg

  • Borderline BP: 120-139/80-89 mmHg

  • Hypertension: ≥ 140/90 mmHg

II. CONTROL OF BP ANATOMIC SITES

• Blood Pressure Equation: $BP = CO imes PVR$

  • BP: Blood pressure

  • CO: Cardiac output

  • PVR: Peripheral vascular resistance

• Four Anatomic Sites of BP Control

  • Arterioles

  • Postcapillary venules (capacitance vessels)

  • Heart

  • Kidney (regulates intravascular fluid volume)

• All antihypertensive agents act on one or more of these four sites to interfere with normal BP-regulating mechanisms.

III. SITES OF ACTION OF THE MAJOR CLASSES OF ANTIHYPERTENSIVE AGENTS

• Figures available in Annex A illustrating sites of action for major antihypertensive drugs.

IV. DRUGS USED IN HYPERTENSION

• Drugs Classification and Mechanisms

  • Diuretics: Lower BP by depleting sodium and reducing blood volume.

  • Sympathoplegic Agents: Lower BP by reducing peripheral vascular resistance, inhibiting cardiac function, and increasing venous pooling.

  • Direct Vasodilators: Reduce pressure by relaxing vascular smooth muscle, thereby dilating resistance vessels and capacitance.

  • Angiotensin Antagonists: Block production of angiotensin, reducing peripheral vascular resistance and potentially blood volume.

V. DIURETICS

• Mechanism of Action

  • Depletes the body of sodium, reducing blood volume.

• Subclasses of Diuretics

  1. Thiazides (Hydrochlorothiazide, Chlorthalidone)

  • Mechanism: Blocks Na/Cl transporter in distal convoluted tubule.

  • Effects: Reduce blood volume and possess unclear vascular effects.

  • Clinical Application: Hypertension, mild heart failure.

  • Pharmacokinetics: Oral, duration of action 8-12 h.

  • Toxicities: Hypokalemia, hyperglycemia, hyperuricemia, hyperlipidemia.

  1. Loop Diuretics (Furosemide)

  • Mechanism: Block Na/K/2Cl transporter in renal loop of Henle.

  • Effects: Greater efficacy in reducing BP.

  • Clinical Application: Severe hypertension, heart failure.

  • Pharmacokinetics: Oral or parenteral, duration of action 2-3 h.

  • Toxicities: Hypokalemia, hypovolemia, ototoxicity.

  1. Potassium-Sparing Diuretics (Spironolactone, Eplerenone)

  • Mechanism: Block aldosterone receptors in renal collecting tubule.

  • Effects: Increase Na and decrease K excretion, with poorly understood reduction in heart failure mortality.

  • Applications: Aldosteronism, heart failure, hypertension.

  • Toxicities: Hyperkalemia, gynecomastia (spironolactone only).

• Summary Table of Diuretic Drugs:

  • Includes subclass, drug names, mechanisms, effects, applications, pharmacokinetics, toxicities, and interactions.

VI. SYMPATHOPLEGICS/BLOCKERS OF

• Centally-Acting Sympathoplegics

  • Drugs: Clonidine, Methyldopa

  • Mechanism: Activate α2 adrenergic receptors, reducing central sympathetic outflow and norepinephrine release.

  • Effects: Lower BP with minimal postural hypotension.

  • Applications: Hypertension (Clonidine also for withdrawal).

  • Toxicity: Sedation; Methyldopa can cause hemolytic anemia.

• β-Adrenoceptor-Blocking Agents

  • Examples: Propranolol, Metoprolol, Atenolol, etc.

  • Mechanism: Reduce BP primarily by decreasing cardiac output and inhibiting renin production via β1 receptors.

  • Clinical Applications: Hypertension, ischemic heart disease, heart failure.

  • Notable Points: Nonselective blockers lead to significant side effects; cardioselective blockers preferred for patients with asthma and peripheral artery disease.

• α1 Blockers

  • Mechanism: Selectively block α1 receptors, leading to dilatation of resistance and capacitance vessels.

  • Clinical Applications: Used for hypertension and benign prostatic hyperplasia.

VII. VASODILATORS

• Types and Uses

  • Hydralazine, Nitroprusside, Calcium Channel Blockers, Nitrates.

• Mechanism of Action

  • Relax vascular smooth muscle, thus dilating resistance vessels and increasing capacitance.

• Calcium Channel Blockers

  • Inhibition of calcium influx into arterial smooth muscle; categorized into dihydropyridines and non-dihydropyridines.

  • Examples and Effects: Nifedipine (less cardiac depression), Verapamil (greatest depressant effect).

VIII. ANGIOTENSIN ANTAGONISTS

• Classifications and Effects

  • ACE Inhibitors: Inhibit angiotensin I conversion to angiotensin II, which is a potent vasoconstrictor.

  • Angiotensin II Receptor Blockers (ARBs): Similar effects without impacting bradykinin metabolism, avoiding certain adverse effects of ACE inhibitors.

  • Renin Inhibitors: Such as Aliskiren.

IX. PHARMACOKINETIC CHARACTERISTICS AND DOSAGE OF SELECTED ORAL ANTIHYPERTENSIVE DRUGS

• Important notes on the need for dosage adjustment with decreased renal function.

X. CLINICAL PHARMACOLOGY OF ANTIHYPERTENSIVE AGENTS

• Confirmation of persistent hypertension and exclusion of secondary causes are critical prior to therapy.

• Factors influencing therapy include BP levels, patient age, organ damage severity, cardiovascular risk factors, and race.

• Essential to educate patients about their condition and the importance of adhering to prescribed medication.

XI. OUTPATIENT THERAPY OF HYPERTENSION

• Lifestyle modifications: sodium restriction, diet rich in fruits, weight reduction, alcohol moderation, and exercise.

• Initial therapy often involves single drugs for mild hypertension and combinatory approaches for moderate to severe cases.

XII. ANTIHYPERTENSIVE AGENTS PREFERRED IN SPECIFIC POPULATIONS

• Tables outlining recommended agents for conditions such as left ventricular hypertrophy, diabetes with proteinuria, and heart failure.

XIII. COMPELLING AND POSSIBLE CONTRAINDICATIONS TO ANTIHYPERTENSIVE AGENTS

• Detailed lists of contraindications for various antihypertensive drug classes, including diuretics, ACE inhibitors, β-blockers, etc.

ANNEXES

• Annex A: Sites of action of Major Antihypertensive Drugs

• Annex B: Sites of action for sympathoplegic agents

• Annex C: Direct Vasodilators

• Annex D: Agents that block production or action of Angiotensin

References:

• Katzung, B. G. (2018). Basic and Clinical Pharmacology (14th edition). Lange Medical Publications.

• Whalen, K., Rajan, R., and Feild, C. (2019). Lippincott Illustrated Reviews Pharmacology (7th edition). Wolters Kluwer.

• Lahoz, G. A. (January 2026). Antihypertensive agents [PPT] & discussion. UNP: College of Medicine.