Hyperreactive Digital Artery Smooth Muscle
Cold or stress triggers exaggerated arterial spasm here.
- High: Resting Ca²⁺ channel activity (placeholder short caption)
- ~4 / wk: Baseline attack frequency (placeholder short caption)
- Narrowed: Digital artery diameter (placeholder short caption)
- Elevated: Trigger sensitivity (placeholder short caption)
Why digital arteries overreact
Placeholder: sympathetic overactivity sensitizes smooth muscle to cold.
Role of L-type calcium channels
Placeholder: channel opening drives the excess contraction.
Nifedipine Occupies L-Type Calcium Channels
A dihydropyridine blocker binds the channel's alpha subunit.
- Dihydropyridine: Drug class (placeholder short caption)
- L-type Ca²⁺ channel: Target (placeholder short caption)
- Alpha-1C subunit: Binding site (placeholder short caption)
- Minutes–hours: Onset (placeholder short caption)
Selectivity for vascular smooth muscle
Placeholder: dihydropyridines favor vessels over cardiac tissue.
Dose-dependent channel occupancy
Placeholder: higher dose blocks a larger channel fraction.
Impaired Calcium Entry Weakens Contraction
Fewer open channels mean less calcium reaches the myofilaments.
- Reduced: Intracellular Ca²⁺ signal (placeholder short caption)
- Lowered: Myosin light-chain activation (placeholder short caption)
- Diminished: Contraction force (placeholder short caption)
- Dose-dependent: Effect scope (placeholder short caption)
Excitation-contraction coupling disrupted
Placeholder: calcium-calmodulin-MLCK pathway loses its driver.
Not a complete blockade
Placeholder: some channels remain open at typical doses.
Smooth Muscle Tone Falls, Blunting Vasospasm
The relaxed vessel resists the usual cold or stress trigger.
- Lowered: Resting vessel tone (placeholder short caption)
- Improved: Digital blood flow (placeholder short caption)
- Blunted: Cold-trigger response (placeholder short caption)
- Modestly higher: Skin temperature (placeholder short caption)
Vasodilation mechanism
Placeholder: relaxed myofilaments widen the arterial lumen.
Symptom relief, not a cure
Placeholder: relaxation reduces but does not remove reactivity.
Fewer and Milder Raynaud's Attacks Over Time
Weeks of steady therapy trend attack frequency downward.
- ~30–50%: Typical frequency reduction (placeholder short caption)
- Also lowered: Severity reduction (placeholder short caption)
- Uncommon: Full elimination (placeholder short caption)
- Weeks–months: Therapy duration (placeholder short caption)
Weekly attack-frequency trend
Placeholder: bars decline as therapy weeks accumulate.
Managing expectations
Placeholder: nifedipine reduces attacks, it rarely eliminates them.
Placeholder highlight: benefit builds gradually across weeks, not instantly.