Metoprolol (generic Lopressor)

What is Metoprolol?

Metoprolol is a prescription drug only obtainable via a doctor’s prescription. Metoprolol also sold under the brand name of Lopressor. Lopressor contains metoprolol tartrate. 

What is Metoprolol used for?

Metoprolol is prescribed to treat high blood pressure and prevent angina (chest pain). The lowering of blood pressure helps reduce the risks of strokes, heart attacks, and kidney problems. 

Metoprolol can also be used to treat chest pain (angina) and improve the survival rate following a heart attack.

How does Metoprolol work?

Blood vessels tighten and subsequently raise the blood pressure of the individual. This causes a massive strain on the heart, increasing the body’s oxygen demand. Metoprolol is classed as a beta-blocker. Its mechanism of action is by relaxing blood vessels and thus slowing the heart and subsequently, the heart rate. Beta-blockers prevent adrenaline/norepinephrine from acting on the beta receptors in the blood vessels and the heart. This causes an improvement in blood flow and lowers blood pressure. 

How long does Metoprolol take to work?

Metoprolol effects start to show within 2 hours after taking the medication, however, it can take up to 1 week to fully take effect. You might not notice any difference after taking Metoprolol, however, this does not mean it is not working. So, it is important to keep taking your medication. Do not stop just because you don’t notice anything. 

How effective is Metoprolol?

Metoprolol has been found to be very effective in treating high blood pressure by a range of studies.

Active ingredients

The active ingredient in Metoprolol is metoprolol tartrate.

Inactive ingredients

The inactive ingredients in Metoprolol include: 

• Cellulose, Microcrystalline
• Silicon Dioxide
• D&C Red No.30 
• Lactose, Unspecified form 
• Magnesium Stearate 
• Polyethylene Glycol, Unspecified 
• Propylene Glycol 
• Povidone 
• Sodium Starch Glycolate Type A Potato
• Talc
• Titanium Dioxide

Please note: inactive ingredients may vary by manufacturer.

Which ingredients can cause an allergic reaction?

If you do have an allergic reaction to metoprolol, you might experience swelling of the lips/face, chest tightness, dizziness, a rash and difficulty breathing. While a severe allergic reaction to metoprolol is rare, if you notice any of these symptoms please make sure to contact medical services right away. 

How to take Metoprolol

Metoprolol is taken orally daily at the same time every day unless specified differently by your healthcare provider.  Metoprolol should be taken with a meal or immediately after food. Metoprolol can be divided in half if told to do so by your healthcare provider. Do not chew or crush your half tablet. 

Metoprolol dosage

The usual initial dosage of Metoprolol is 100mg daily. After, the dosage is increased in increments until optimum blood pressure is reached.  The maximum effects of Metoprolol are noticed after a week. The effective dose of Metoprolol is between 100mg and 450mg. 

What should I do if I miss a dose of Metoprolol?

Take Metoprolol as soon as you realise that you have missed your dose unless it is nearly time to take your next dose. If this happens, take the next dose as per normal and forget your missed dose. Never double a dose if you missed your last dose. If you regularly find yourself missing doses, set an alarm to help remind yourself. 

What strengths of Metoprolol are available?

Generic Metoprolol is available in two forms:

• Immediate-release oral tablet (metoprolol tartrate) - 25 mg, 37.5 mg, 50 mg, 75 mg, and 100 mg
• Extended-release oral tablet (metoprolol succinate) - 25 mg, 50 mg, 100 mg, and 200 mg

The Lopressor brand of Metoprolol is available as follows:

• Immediate-release oral tablet (metoprolol tartrate) - 50 mg and 100 mg

Metoprolol side effects

Common side effects of Metoprolol:

These side effects are found to happen in more than 1% of people. They are usually mild and don’t last very long. If these side-effects bother you or last for more than a few days, seek medical advice. The side effects are:

• Headaches 
• Tiredness, dizziness or weakness
• Cold hands or feet
• Nausea
• Stomach ache 

Serious side effects: 

• Shortness of breath, wheezing and chest tightness - signs of lung problems
• Shortness of breath with a cough worsening during exercise, swollen ankles or legs, chest pain, irregular heartbeat - signs of heart problems 
• Fast heart rate, high temperature (38C or higher), trembling and confusion - signs of elevated thyroid levels in the blood
• Yellow skin or the yellowing of the whites of your eye - signs of liver problems

These side effects are rare but can be experienced by some people. Contact your doctor immediately if you experience them. 

Drug interactions

Metoprolol can affect other drugs if taken together. It is important to let your doctor know if take any of these medications. 
Types of drugs that interact with Metoprolol include:

• Antidepressants including bupropion (Wellbutrin), fluoxetine (Prozac, Sarafem), and paroxetine (Paxil)
• Antimalaria drugs such as hydroxychloroquine
• Medications used to treat heartburn or other stomach conditions, such as cimetidine (Tagamet) and ranitidine (Zantac)
• Some heart medications, including clonidine (Catapres), propafenone (Rythmol), and quinidine (Quinaglute, Quinidex)
• Antihistamines like diphenhydramine (Benadryl)
• Certain HIV drugs, including ritonavir (Norvir)
• Some antifungal medications, including terbinafine (Lamisil)
• Certain drugs used to treat mental illness, including thioridazine (Mellaril)

Contraindications

Metoprolol tartrate oral medication is contraindicated in these conditions:

• Sinus bradycardia 
• Heart block greater than first degree
• Cardiogenic shock
• Overt cardiac failure

Metoprolol and pregnancy

Metoprolol should be stopped once a pregnancy has been confirmed. It should only be used if the benefits outweighs the risk. It is important to let your doctor know if you’re pregnant. 

If Metoprolol is used during pregnancy, the lowest possible dose will be administered and it will be discontinued 2-3 days prior to delivery.

Metoprolol vs Atenolol

Metoprolol and atenolol are very similar drugs. They both treat high blood pressure and are beta-blocker drugs. They also have similar side effects and both come in tablet form. The only difference is that Metoprolol can still be taken during pregnancy is needed, however, atenolol should not be taken during pregnancy.