GuanfacineGuanfacine Hydrochloride

About Guanfacine

Guanfacine acts on alpha-2A adrenergic receptors in the brain and is not a stimulant; the label says how it helps ADHD is not known. Immediate-release tablets are labeled for high blood pressure, alone or with other medicines, especially thiazide diuretics: the usual start is 1 mg at bedtime, to minimize sleepiness, rising to 2 mg after three to four weeks if needed, and safety and effectiveness under age 12 have not been shown. Extended-release tablets are labeled for ADHD, alone or added to a stimulant; their trials enrolled children and teens 6 to 17, and safety and effectiveness under 6 have not been established. They start at 1 mg once a day, in the morning or evening, rising by no more than 1 mg a week toward 0.05 to 0.12 mg per kg a day; doses above 4 mg were not studied in children 6 to 12 or with a stimulant, nor above 7 mg in teens 13 to 17.

Neither form has a boxed warning, and guanfacine must not be taken by anyone allergic to it. It can lower blood pressure and heart rate and cause fainting, so both are measured before starting, after dose increases and periodically, and people prone to fainting avoid dehydration and overheating. It causes sleepiness, especially at first, which alcohol and other sedatives deepen, so driving waits until its effect is known, and it can worsen some heart conduction problems. Stopping suddenly can make blood pressure rebound, so the extended-release dose is lowered by no more than 1 mg every 3 to 7 days. In ADHD monotherapy trials, low blood pressure, sleepiness, fatigue, nausea and lethargy were most common; with immediate-release tablets, dry mouth, sleepiness, weakness, dizziness, headache, impotence, constipation and fatigue.

Guanfacine is not a controlled substance, so prescriptions can carry refills. The extended-release tablet must not be substituted milligram for milligram for immediate-release tablets, and MedlinePlus warns against taking both; using immediate-release tablets for ADHD is not an FDA-approved use, so that choice rests with the prescriber. Extended-release tablets are swallowed whole and not taken with a high-fat meal, which raises how much is absorbed, and after two or more missed doses the prescriber may rebuild the dose gradually. Strong or moderate CYP3A4 inhibitors such as ketoconazole call for halving the extended-release dose, and inducers such as rifampin for up to double. The Intuniv label advises watching a breastfed baby for sleepiness, lethargy and poor feeding. Tenex is discontinued in every strength; Intuniv is still sold.

Taking Guanfacine

How to take it

Immediate-release tablets: usually once a day at bedtime. Extended-release tablets: once a day, morning or evening, swallowed whole without crushing, chewing or breaking, and not with a high-fat meal. Do not stop either form suddenly.

If you miss a dose

Take it as soon as you remember, unless the next dose is almost due; then skip it, and do not take a double dose. If you miss two or more extended-release doses in a row, call the prescriber.

Storage

At room temperature in the original, tightly closed container, away from excess heat and moisture (not in the bathroom), out of reach of children. Do not flush it; use a take-back program.

Interactions to know about

Ketoconazole, fluconazole and other CYP3A4 inhibitors raise its levels, and rifampin and efavirenz lower them, so the extended-release dose may need to be halved or raised. Alcohol and other sedatives add to sleepiness, and blood pressure medicines to its effects; MedlinePlus advises asking about grapefruit, St. John’s wort and allergy medicines such as diphenhydramine.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Guanfacine differs from pharmacy to pharmacy

Both forms are generic with many makers, but they are separate products: a prescription for one can be filled only with that form, and an extended-release prescription can be filled with any generic rated equivalent to Intuniv unless it names the brand and blocks substitution. Extended-release doses above 4 mg take two tablets a day. Each pharmacy sets its own cash price, including its dispensing fee.

Ways to pay less for Guanfacine without insurance

• Ask whether guanfacine is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• Once your dose is settled, ask for a ninety-day supply; guanfacine is not controlled, so the prescription can carry refills.
• Make sure an extended-release prescription does not name Intuniv only, so a rated generic can be dispensed.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Guanfacine

1. 1.Is my prescription for immediate-release or extended-release guanfacine?
2. 2.Is it safe with my blood pressure medicine, a stimulant or medicines that make me sleepy?
3. 3.Do any of my antifungal, antibiotic or HIV medicines change its levels?
4. 4.How should my dose be lowered if I need to stop?

Related medications