Calcium Channel Blockers

Question 1

How do calcium channel blockers work?

Answer 1

• have different affinities for different sites, hence different therapeutic effects
• interfere with inward displacement of calcium ions through slow channels of active cell membranes

Question 2

Three different classes

Answer 2

1) Dihydropyridines
2) Phenylaklyamines
3) Benzothiazepines

Question 3

Dihydropyridines CCB

Answer 3

EXAMPLES - Amlodpines, nifedipine (maintain same brand for MR), Lercanidipine, lacidipine and felodipine

• Relax vascular smooth muscle (predominantly vasodilators effects)
• Have no anti - arrhythmic activity

Question 4

Phenylalkylamines eg. Verapamil (avoid in heart failure)

Answer 4

Verapamil:
- used to treat hypertension, angina,arrhythmias
- highly negatively inotrpic CCB so slow heart rate
- minimal vasodilators effects in comparison to Dihydropyridines
- causes constipation
- has profound cardiac depressant effects and may precipitate heart failure
- do not use with BB, causes bradycardia,hypotension - especially IV verapamil

Question 5

Benzothiazepines - eg. Diltiazem (avoid in heart failure)

Answer 5

• have both cardiac depressant and vasodilatory effects
• intermediate between phenylalkylamines and Dihydropyridines
• effective in most forms of angina
• longer acting formulations used for hypertension
• may be used for patients where BB are contraindicated or ineffective
• less negative inotropic effect than verapamil
• use with caution with BB (because of risk of bradycardia)

Question 6

Unstable Angina

Answer 6

CCB do not reduce the risk of myocardial infarction in unstable angina
- verapamil and diltiazem should be reserved for patients resistant to treatment with BB
- Sudden withdrawal of CCB may exacerbate angina

Question 7

Prescribing and dispensing diltiazem

Answer 7

Different versions of MR preps containing more than 60mg may not have the same clinical effects
- prescribers need to prescribe as brand

Question 8

Other anti-angina drugs - Nicorandil

Answer 8

Licensed for long term treatment of angina

Has both arterial and venous vasodilatory effects

Potassium channel activators with nitrate component

Other drugs - ivabadrine and ranolazine

Question 9

Side effects of CCB

Answer 9

Vasodilatory effects
- dizziness
- flushing
-headaches
-postural hypotension
- GI disturbances
- Ankle swelling
- Skin reactions
!!!!!! Sudden withdrawal may exacerbate myocardial ischaemia!!!