dipyridamole

BEERS REMS

PO: Prevention of thromboembolism in patients with prosthetic heart valves (with warfarin).
Maintains patency after surgical grafting procedures, including coronary artery bypass (with aspirin).
IV: As an alternative to exercise in myocardial perfusion scintigraphy (cardiac stress testing with radiotracer imaging).

Action ⬆ ⬇

PO: Decreases platelet aggregation by inhibiting the enzyme phosphodiesterase.
IV: Produces coronary vasodilation by inhibiting adenosine uptake.

Therapeutic effects:

PO: Inhibition of platelet aggregation and subsequent thromboembolic events.
IV: In diagnostic thallium imaging, dipyridamole dilates normal coronary arteries, reducing flow to vessels that are narrowed and causing abnormal thallium distribution.

Pharmacokinetics ⬆ ⬇

Absorption: Moderately absorbed (30–60%) after oral administration. IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Metabolized by the liver; excreted in the bile.

Half-Life: 10 hr.

Time/Action Profile ⬆ ⬇

(PO = antiplatelet activity, IV = coronary vasodilation)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	unknown	unknown
IV	unknown	6.5 min‡	30 min

‡From start of infusion.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity.

Use Cautiously in:

Hypotension;
Patients with platelet defects;
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Children <12 yr (safety and effectiveness not established);
Geri: Appears on Beers list. Older adults may have ↑ risk of orthostatic hypotension with oral, short-acting formulation. Avoid use of oral, short-acting formulation in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypotension, arrhythmias, flushing, IV onlyMI

GI: nausea, diarrhea, GI upset, vomiting

Derm: rash

Neuro: dizziness, headache, syncope, IV onlytransient cerebral ischemia, weakness

Resp: IV onlybronchospasm

Interactions ⬆ ⬇

Drug-drug:

Additive effects with aspirin on platelet aggregation.
Risk of bleeding may be ↑ when used with anticoagulants, thrombolytic agents, NSAIDs, cefotetan, or valproic acid.
↑risk of hypotension with alcohol.
Theophylline may negate the effects of dipyridamole during diagnostic thallium imaging.

Route/Dosage ⬆ ⬇

PO (Adults ): 225–400 mg/day in 3–4 divided doses.
IV (Adults ): 570 mcg/kg; maximum dose 60 mg.

Availability ⬆ ⬇

(Generic available)

Tablets: 25 mg; 50 mg; 75 mg
Solution for injection: 5 mg/mL
In combination with: aspirin.

Assessment ⬆ ⬇

PO: Monitor BP and pulse before starting therapy and regularly during period of dose adjustment. Geri: Assess geriatric patients for orthostatic hypotension.
IV: Monitor vital signs during and for 10–15 min after infusion. Obtain ECG in at least 1 lead. If severe chest pain or bronchospasm occurs, administer IV aminophylline 50–250 mg at a rate of 50–100 mg over 30–60 sec. If hypotension is severe, place patient in a supine position with head tilting down. If chest pain is unrelieved with aminophylline 250 mg, administer nitroglycerin SL. If chest pain is still unrelieved, treat as myocardial infarction.

Lab Test Considerations:

Monitor bleeding time periodically during therapy.

Implementation ⬆ ⬇

PO: Administer with a full glass of water at least 1 hr before or 2 hr after meals for faster absorption. If GI irritation occurs, may be administered with or immediately after meals. Tablets may be crushed and mixed with food if patient has difficulty swallowing. Pharmacist may make a suspension.
- Discontinue for 48 hr prior to undergoing stress testing with IV dipyridamole, adenosine, or regadenoson.

IV Administration:

Intermittent Infusion: Diluent: Dilute in at least a 1:2 ratio of 0.45% NaCl, 0.9% NaCl, or D5W for a total volume of 20–50 mL. Undiluted dipyridamole may cause venous irritation.
Rate: Infuse over 4 min.

Patient/Family Teaching ⬆ ⬇

PO: Instruct patient to take medication at evenly spaced intervals as directed. Take missed doses as soon as remembered unless the next scheduled dose is within 4 hr. Do not double doses. Benefit of medication may not be apparent to patient; encourage patient to continue taking medication as directed.
- Caution patient to change positions slowly to minimize orthostatic hypotension.
- Advise patient to avoid the use of alcohol, as it may potentiate the hypotensive effects. Tobacco products should also be avoided because nicotine causes vasoconstriction.
- Advise patient to consult health care professional before taking OTC medications concurrently with this medication. Aspirin should be taken only if directed and only in dose prescribed. Advise patient to discuss alternatives for pain relief or fever.
- Instruct patient to notify health care professional if unusual bleeding or bruising occurs. Concurrent use of aspirin or warfarin may increase risk of bleeding but is commonly used with specific indications.
Advise patient to notify health care professional of medication regimen and whether using concurrent aspirin or warfarin therapy.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
IV: Instruct patient to notify health care professional immediately if dyspnea or chest pain occurs.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇