MANAGEMENT
It is not wise to commence treatment at the first diagnosis itself unless there is malignant hypertension, end-organ damage (see below) or significant other vascular risk factors, or comorbidity. (Treat with antihypertensive agents if the diastolic pressure is > 100 mmHg, or systolic > 200 mmHg, or systolic pressure > 160 mmHg together with end-organ damage. The presence of other cardiovascular risk factors would be another indication for treatment.) Observation for 3–6 months with recommendation of non-pharmacological methods such as progressive muscle relaxation, weight reduction (if relevant), reduction of alcohol consumption, salt restriction and regular physical exercise would suffice initially. It is important to advise the patient against smoking. If present, hyperlipidaemia and diabetes should be treated. If the blood pressure remains elevated (>140/90 mmHg) despite adequate lifestyle modification (or due to failure of lifestyle modification), pharmacotherapy should be initiated.
End-organ damage due to hypertension
• Myocardial infarction
• Left ventricular hypertrophy
• Cardiac failure
• Stroke
• Hypertensive nephropathy
• Hypertensive retinopathy
• Arteriosclerosis
Selection of the appropriate antihypertensive agent should be guided by several factors, including: the patient’s comorbidities, age, sex, ethnic background and drug allergies. Initially an attempt should be directed at monotherapy, and the commonly used agents are thiazide diuretics, beta-blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blocker (ARB). If monotherapy is inadequate, combination therapy can be considered. An ACE inhibitor with a diuretic, or a beta-blocker with a diuretic, are two such combinations. There are combination pills containing an ACE inhibitor or an ARB together with a thiazide diuretic that can be prescribed. Hypertension that is not well controlled with conventional agents even with up titration and combination warrants further investigation and the addition of potent, less commonly used agents such alpha receptor blockers, centrally acting agents or arterial vasodilators.
Comorbidities that can influence the choice of therapy
• Diabetes mellitus —ACE inhibitors are the most suitable agents. Where ACE inhibitors are not tolerated, the other options to consider include ARBs and calcium channel blockers. Beta-adrenergic receptor blockers and thiazide diuretics can interfere with glycaemic control. ACE inhibitors and ARBs have significant and useful synergy in severe high blood pressure and diabetic nephropathy.
• Gout —beta-blockers, ACE inhibitors, calcium channel blockers and alphablockers are suitable. Thiazide diuretics can exacerbate gout.
• Dyslipidaemia —ACE inhibitors, calcium channel blockers and alpha-blockers are recommended. Beta-blockers may be less desirable due to their adverse effects on the lipid profile.
• Ischaemic heart disease —diuretics, beta-blockers, calcium channel blockers, ACE inhibitors and ARBs are suitable because of their protective properties in coronary vascular disease.
• Congestive cardiac failure —ideal agents include beta-blockers, ACE inhibitors, ARBs and diuretics, which also have proven value in the management of cardiac failure.
• Peripheral vascular disease —calcium channel blockers, alpha-adrenergic receptor blockers and diuretics are desirable agents. Beta-blockers are contraindicated.
• Pregnancy —for mild hypertension in pregnant patients, methyldopa and the alpha- and beta-adrenergic receptor blocking agent labetolol are good choices. In preeclampsia, nifedipine is a suitable agent; however, urgent delivery of the baby is an absolute requirement. Severe hypertension in the pregnant patient can be managed with intravenous (IV) hydralazine.
Adverse effects of some antihypertensive agents
It is important to have a commanding knowledge of the properties and adverse effects of the commonly used antihypertensive agents. Below is a list of adverse effects seen with different classes of antihypertensive agents, together with some important properties of selected agents.
• Thiazide diuretics —hypercholesterolaemia, hyperglycaemia, thrombocytopenia and gout • Beta-blockers —bradycardia, postural hypotension, depression and cold peripheries.
• ACE inhibitors —angio-oedema, cough, postural hypotension, hyperkalaemia, progression of renal failure and first-dose hypotension. First-dose hypotension is a rarity but is seen particularly in patients on low-sodium diets and high-dose diuretics.
• Angiotensin II receptor blockers —similar to ACE inhibitors but cough is less common
• Calcium channel blockers —headaches, sweating, palpitations and ankle oedema
• Alpha-blockers —first-dose hypotension. Long-acting alpha-blockers such as doxazocin have less first-dose hypotension effect.
• Vasodilators —minoxidil is an agent used in resistant hypertension. It is one of the most potent antihypertensive drugs available. Minoxidil can cause sodium and water retention, leading to ankle oedema and, in the rare case, pericardial effusion. Another undesirable side effect of minoxidil is hypertrichosis.
Hydralazine has its use in pregnancy and sometimes in cardiac failure. Hydralazine can cause drug-induced lupus. Nitroprusside is another vasodilator agent that is used in hypertensive crises and dissection of the aorta.
