Amlodipine side effects: what to expect and when to worry

As a calcium channel blocker, amlodipine works by relaxing blood vessel walls, which effectively lowers blood pressure but also causes predictable side effects related to vasodilatation.

• Peripheral oedema (ankle swelling): the most characteristic side effect, affecting up to 10% of patients on 5 mg and up to 30% on 10 mg. This is not fluid retention in the traditional sense but rather redistribution of fluid into the tissues due to preferential arteriolar dilatation
• Flushing: a sensation of warmth and redness, particularly in the face and neck. More common in the first week of treatment
• Headache: related to cerebral vasodilatation, typically settles within 1 to 2 weeks
• Dizziness: particularly on standing, due to blood pressure reduction
• Fatigue and somnolence: some patients feel unusually tired in the first few days
• Palpitations: an awareness of the heartbeat, usually benign but can be alarming
• Abdominal pain and nausea: gastrointestinal symptoms are occasionally reported

I find that the most problematic side effect in practice is ankle swelling, which is both common and distressing for patients.

It is important to understand that this is a pharmacological effect of the drug rather than a sign of heart failure.

Elevating the legs, wearing compression stockings and taking the dose in the evening can all help to mitigate this.

Peripheral oedema is the side effect that most often leads patients to request a change in their blood pressure medication. Understanding its mechanism helps in management.

Why amlodipine causes swelling:

Amlodipine dilates arterioles (small arteries) more than venules (small veins).

This creates an imbalance in capillary pressure: more blood flows into the tissues through the dilated arterioles, but drainage through the venous system does not increase proportionally.

The result is fluid accumulation in dependent areas, particularly the ankles and feet.

Important distinction:

This is not the same as fluid overload seen in heart failure or kidney disease. Diuretics are generally ineffective because the problem is pressure-related rather than volume-related.

Practical management strategies:

1. Dose reduction: reducing from 10 mg to 5 mg can significantly improve oedema while maintaining blood pressure control
2. Adding an ACE inhibitor or ARB: drugs like ramipril or losartan dilate the venous side, helping to restore capillary pressure balance. This is why combination therapy often resolves the swelling
3. Evening dosing: taking amlodipine at bedtime means the peak drug effect occurs while the legs are elevated during sleep
4. Leg elevation: raising the feet when sitting, ideally above heart level
5. Compression stockings: graduated compression hosiery (class 1 or 2) can reduce fluid accumulation
6. Regular walking: calf muscle activity promotes venous return

If swelling is severe despite these measures, your GP may consider switching to a different antihypertensive.

Lercanidipine, a newer dihydropyridine calcium channel blocker, is associated with less oedema than amlodipine.

While less frequently encountered, these side effects are listed in the BNF and are worth knowing about.

Uncommon (1 in 100 to 1 in 1,000):

• Mood changes: including depression and anxiety
• Tremor and paraesthesia: tingling or numbness in the extremities
• Visual disturbance: blurred vision, which usually resolves with continued treatment
• Tinnitus: ringing in the ears
• Dyspnoea: shortness of breath, typically mild
• Rhinitis: nasal congestion and runny nose
• Alopecia: hair thinning is occasionally reported
• Skin rash and pruritus: mild allergic skin reactions
• Myalgia: muscle pain, which should be distinguished from the effects of concurrent statin therapy

Rare (1 in 1,000 to 1 in 10,000):

• Gingival hyperplasia: overgrowth of the gum tissue, a class effect of calcium channel blockers. Good dental hygiene reduces the risk. If significant, the drug should be stopped
• Gynaecomastia: breast enlargement in males has been reported in isolated cases
• Hepatitis: very rare liver inflammation, presenting with jaundice and malaise
• Erythema multiforme: a serious skin reaction requiring immediate medical attention

I always counsel patients that rare side effects are, by definition, uncommon.

The vast majority of patients taking amlodipine experience either no side effects or only the common vasodilatory symptoms described above.

Amlodipine is metabolised by CYP3A4 in the liver, which creates potential interactions with other medications. The BNF highlights several clinically important considerations.

Key drug interactions:

• Simvastatin: the maximum dose of simvastatin should not exceed 20 mg daily when taken with amlodipine, due to increased risk of myopathy. This interaction does not apply to atorvastatin or rosuvastatin
• CYP3A4 inhibitors (e.g. clarithromycin, ketoconazole, grapefruit juice): these can increase amlodipine levels, potentially causing excessive blood pressure reduction
• CYP3A4 inducers (e.g. rifampicin, carbamazepine, St John's wort): these may reduce amlodipine efficacy
• Other antihypertensives: additive blood pressure lowering effect, which is usually intentional but requires monitoring
• Ciclosporin: amlodipine may increase ciclosporin levels; monitoring is required

Precautions:

• Heart failure: amlodipine can be used cautiously in stable heart failure but should be avoided in acute decompensation
• Aortic stenosis: use with caution due to the risk of reduced coronary perfusion
• Hepatic impairment: start with a lower dose (2.5 mg) as amlodipine clearance is reduced

Grapefruit interaction:

Unlike some other calcium channel blockers, the clinical significance of grapefruit juice interaction with amlodipine is considered modest.

However, I still advise patients to avoid consuming large quantities of grapefruit or grapefruit juice during treatment.

While amlodipine has an excellent safety profile, there are circumstances where medical review is warranted.

See your GP if:

• Ankle swelling is severe, painful or affecting your mobility
• You develop swelling in only one leg (this may indicate a different cause such as DVT rather than a drug side effect)
• Headaches or dizziness persist beyond 2 to 3 weeks of starting or increasing the dose
• You develop persistent palpitations or feel your heart is beating irregularly
• You notice gum overgrowth or bleeding gums
• You experience persistent mood changes or low mood
• Your blood pressure is consistently below 90/60 mmHg (if you monitor at home)

Seek urgent medical attention if:

• You experience severe chest pain (amlodipine is used to treat angina, so new chest pain needs assessment)
• You develop a widespread skin rash with blisters or mucosal involvement (possible Stevens-Johnson syndrome, extremely rare)
• You feel faint or collapse, particularly on standing
• You develop severe abdominal pain with jaundice

It is worth noting that amlodipine has a very long half-life (30 to 50 hours), which means that side effects may take several days to improve after dose reduction or discontinuation.

Patience is important when making changes to this medication.

The NHS information page provides further guidance on when and how to contact your healthcare team.