Amlodipine (besylate)

What is this medication for?

• Systemic high blood pressure (usually secondary to CKD, hyperthyroidism, cardiac disease) — drug of choice for most clinicians
• Systemic high blood pressure (e.g., chronic renal disease); adjunctive afterload reducer in refractory CHF from mitral valve degeneration

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Cat high blood pressure target: start 0.625 mg/cat once daily, double only after 1–2 weeks if systolic still >160 mmHg. Missing doses → high blood pressure rapidly recurs.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Gingival hyperplasia (Long-term use; resolves on discontinuation)
• Anorexia early in therapy (Possible)

Worth a phone call to your veterinarian

• Hypotension, rising kidney values, low energy/tiredness, hypokalemia, reflex unusually fast heart rate, weight loss (Infrequent (slow onset limits acute low blood pressure))

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Slight negative inotrope — caution in heart failure/cardiogenic shock, advanced aortic stenosis, hepatic disease, dehydration, patients at risk of low blood pressure
• has or has had: Monotherapy in renal-disease cats may raise intraglomerular pressure via RAAS activation — ACE-inhibitor co-therapy debated but often considered in proteinuric patients

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Diuretics, beta-blockers, other vasodilators, fentanyl
  • Grapefruit juice

Storage and handling

Room temperature, tight container, protect from light. Unstable if tablets are split or compounded — potency not assured (Papich; tablets are difficult to split for small patients).

Good to know

• Cat high blood pressure target: start 0.625 mg/cat once daily, double only after 1–2 weeks if systolic still >160 mmHg. Missing doses → high blood pressure rapidly recurs.
• Cats respond better to amlodipine than to ACE inhibitors; dogs are the opposite (amlodipine disappointing as monotherapy, partly because it activates RAAS at higher doses).
• ~50% of cats acutely blind from high blood pressure may regain some vision if treatment starts promptly.
• Overdose: low blood pressure ± reflex unusually fast heart rate/unusually slow heart rate — manage with gut emptying, into a vein fluids, calcium, beta-agonists, into a vein lipid.