Blood Pressure Drugs
Used in many heart conditions, these drugs reduce arteriolar constriction and thus afterload
Nitrovasodilators
e.g. Amyl nitrate + Glyceryl trinitrate + Isosorbide dinitrate
These drugs are converted to nitric oxide in vascular smooth muscle cells
– This activates cGMP-dependent kinases –> PKG –> phosphorylation of MLCK –> smooth muscle relaxation –> vascular dilation
– They dilate veins reducing cardiac preload but also arterioles reducing afterload
– Unlike other vasodilators, these drugs preferentially dilate collaterals in ischaemic areas rather than well-oxygenated areas. It helps the areas which need blood most preventing “coronary steal.”
- Amyl nitrate – volatile liquid inhaled for acute attacks
- Glyceryl trinitrate + Isosorbide dinitrate – these are taken sublingually
Side effects
Hypotension with reflex tachycardia
Throbbing headache
Dizziness
Development of tolerance
Contraindications
- Hypotension (BP<90)
- Aortic stenosis
Dihydropyridines
e.g. Amlodipine + Nifedipine + Nimodipine
These are L-type calcium channel blockers, that bind to the inactive form of the channel.
– As they bind inactive form of channel, this gives them selectivity for vascular smooth muscle rather than cardiac muscle, meaning that they give vasodilation and decrease afterload
– They are often combined with beta-blockers in order to prevent a reflex tachycardia
Side effects
Vasodilation –> flushing and headaches
Ankle oedema
Alpha receptor antagonists
These lower total peripheral resistance by stopping sympathetic system action on a1 receptor
Phentolamine
This is a non-selective a-antagonist, gives vasodilation but also a reflex tachycardia
Prazosin + Terazosin
These are alpha-1-selective antagonists.
– Do not cause a reflex tachycardia but can give orthostatic hypotension (when patient stands)
Labetalol
This is a mixed alpha – and B- adrenoceptor antagonist
K+ channel openers
These act on ATP-sensitive K+ channels in vascular smooth muscle
– ATP usually closes these channels, these drugs open the channels enhancing outward K+ current
– This causes cell hyperpolarisation –> muscle relaxation –> vasodilation
e.g. Minoxidil
This is used to treat refractory hypertension + hair loss (causes hirsutism)
Side effects
Causes reflex tachycardia so combined with a B-blocker + Diuretic.
Nicorandil
This is used in angina to open cardiac KATP channels to improve coronary blood flow
Side effects
- Flushing + Headache, nausea + vomiting, rectal bleeding
Dipyridamole
This is a phosphodiesterase inhibitor and so dilates resistance vessels
– Also interferes with adenosine breakdown which stops platelet aggregation
– Used in acute coronary syndrome as an antiplatelet agent (second line after clopidogrel)
Central Sympathetic Agents
These drugs work on different levels of the sympathetic nervous system to decrease peripheral vascular resistance
Reserpine [Storage]
Prevents vesicle storage of Na by inhibiting the VMAT transporter
– Therefore, NA leaks out of the terminal causing depletion from the sympathetic nerve terminal
– This leads to less sympathetic outflow causing vasodilation

Methyldopa [Release]
This is a variant of Dopa, a precursor in the noradrenaline synthesis pathway
– This instead gets converted to methyl-noradrenaline which is a false neurotransmitter
– It binds presynaptic inhibitory a2 receptors which are Gi coupled, causing hyperpolarisation
– This inhibits the presynaptic terminal reducing NA release decreasing sympathetic outflow, leading to downstream vasodilation
– It is used to manage hypertension during pregnancy
Clonidine + Monoxidine [Release]
These are a2 receptor agonists which stimulate pre-synaptic a2– adrenoceptors
– They inhibit the synaptic terminal in the CNS decreasing sympathetic outflow, leading to downstream vasodilation

Hydralazine
This reduces blood pressure directly by relaxing arteriolar muscle
Side effects
Can cause lupus-like (SLE) syndrome
Sodium Nitroprusside
This is metabolised to NO, causing dilation of arterioles + veins.
Side effects
- Can be converted to cyanide –> risk of toxicity
Pulmonary hypertension drugs
Many of these drugs work by inhibiting the endothelium to stop making endothelin
– Endothelin is a vasoconstrictor and activates local renin-angiotensin systems in lungs.
- Ambrisentan – selective endothelin A receptor competitive antagonist
- Bosentan – antagonises both endothelin A and B receptors to lower BP
Side effects
- Interact with ciclosporin
- Can cause oedema/elevated LFTs
Erectile Dysfunction drugs
Some vasodilators are used to decrease pelvic vessel resistance to treat erectile dysfunction.
e.g. Sildenafil (Viagra) + Tadalafil
These drugs inhibit phosphodiesterase type V
– Increases cGMP levels –> phosphorylates MLCK –> smooth muscle relaxes –> vasodilation
– They can also be used to treat pulmonary hypertension + Raynaud’s phenomenon
Side effects
Back pain and myalgia
Headache + Flushing
Nasal congestion
Blurred vision with blue tint
Contraindications
Degenerative retinal disorders
Recent stroke, MI or unstable angina
Hypotension (systolic <90mmHg)
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