Generic Isoptin has been used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, and most recently, cluster headaches. It is also an effective preventive medication for migraine. It has also been used as a vasodilator during cryopreservation of blood vessels. It is a class IV antiarrhythmic, more effective than digoxin in controlling ventricular rate.

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results.

Do not crush, chew, break, or open an extended-release tablet or capsule. Swallow it whole. Breaking or opening the pill may cause too much of the drug to be released at one time.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• fast or slow heartbeats;
• feeling like you might pass out;
• fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;
• restless muscle movements in your eyes, tongue, jaw, or neck;
• feeling short of breath, even with mild exertion;
• swelling, rapid weight gain; or
• nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Less serious side effects may include:

• constipation, nausea;
• skin rash or itching;
• dizziness, headache, tired feeling; or
• warmth, itching, redness, or tingly feeling under your skin.

This is not a complete list of side effects and others may occur.

You should not use verapamil if you are allergic to it, or if you have certain serious heart conditions such as "sick sinus syndrome" or "AV block" (unless you have a pacemaker), low blood pressure, or if you have recently had a heart attack.

Generic Isoptin may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Drinking alcohol can further lower your blood pressure and may increase certain side effects of Generic Isoptin.

Grapefruit and grapefruit juice may interact with Generic Isoptin and lead to potentially dangerous effects. Discuss the use of grapefruit products with your doctor.

Many drugs can interact with Generic Isoptin. Below is just a partial list. Tell your doctor if you are using:

• buspirone (BuSpar);
• cimetidine (Tagamet);
• Generic Clonidine (Catapres, Clorpres, Kapvay, Nexiclon) or any other blood pressure medications;
• cyclosporine (Gengraf, Neoral, Sandimmune);
• digoxin (digitalis, Lanoxin, Lanoxicaps);
• lithium (Eskalith, LithoBid);
• lovastatin (Mevacor, Advicor) or simvastatin (Zocor, Simcor, Vytorin);
• theophylline (Elixophyllin, Theo-24, Uniphyl);
• an antibiotic such as clarithromycin (Biaxin), erythromycin (E.E.S., EryPed, Ery-Tab, Erythrocin, Pediazole), rifampin (Rifadin, Rimactane, Rifater), or telithromycin (Ketek);
• an antifungal medication such as fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), or voriconazole (Vfend);
• a beta-blocker such as atenolol (Tenormin), bisoprolol (Zebeta, Generic Ziac), metoprolol (Lopressor, Toprol), propranolol (Inderal, InnoPran), sotalol (Betapace), timolol (Blocadren), and others;
• cancer medicine such as cisplatin (Platinol), cyclophosphamide (Cytoxan, Neosar), doxorubicin (Adriamycin), paclitaxel (Taxol), procarbazine (Matulane), vincristine (Oncovin), or vinorelbine (Navelbine);
• cholesterol-lowering drugs such as atorvastatin (Lipitor, Caduet), lovastatin (Mevacor, Altoprev, Advicor), or simvastatin (Zocor, Simcor, Vytorin, Juvisync);
• a heart rhythm medication such as amiodarone (Cordarone, Pacerone), Generic Norpace (Norpace), flecainide (Tambocor), or quinidine (Quin-G);
• HIV/AIDS medicine such as Generic Atazanavir (Reyataz), delavirdine (Rescriptor), fosamprenavir (Lexiva), indinavir (Crixivan), nelfinavir (Viracept), or ritonavir (Norvir, Kaletra);
• a sedative such as midazolam (Versed) or triazolam (Halcion); or
• seizure medication such as carbamazepine (Carbatrol, Equetro, Tegretol) or phenobarbital (Solfoton).

This list is not complete and other drugs may interact with Generic Isoptin.

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Store at room temperature away from moisture, heat, and light. Keep away from children and pets.