6 Interactions found for:
Drug Interactions
No drug interactions were found for selected drugs: allopurinol, Metoprolol Succinate ER.
This does not necessarily mean no interactions exist. Always consult your healthcare provider.
Drug and Food Interactions
Moderate
Allopurinol
+ Food
The following applies to the ingredients: Allopurinol
Allopurinol should generally be taken after a meal to reduce side effects. If your daily dose exceeds 300 mg, you may also ask your healthcare provider if it is okay to divide the total daily dose into smaller doses given more frequently instead of once a day, as this may also reduce stomach upset that can happen with allopurinol. It is best to avoid or limit the consumption of alcohol, as it can increase drowsiness or other nervous system side effects of allopurinol. You should also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
Moderate
Metoprolol Succinate Er
+ Food
The following applies to the ingredients: Metoprolol (found in Metoprolol Succinate Er)
Food can enhance the levels of metoprolol in your body. You should take metoprolol at the same time each day, preferably with or immediately following meals. This will make it easier for your body to absorb the medication. Avoid drinking alcohol, which could increase drowsiness and dizziness while you are taking metoprolol. Metoprolol is only part of a complete program of treatment that also includes diet, exercise, and weight control. Follow your diet, medication, and exercise routines very closely.
The following applies to the ingredients: Metoprolol (found in Metoprolol Succinate Er)
Using metoprolol together with multivitamin with minerals may decrease the effects of metoprolol. Separate the administration times of metoprolol and multivitamin with minerals by at least 2 hours. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
Drug and Pregnancy Interactions
Major
Allopurinol
+ Pregnancy
The following applies to the ingredients: Allopurinol
Professional Content
Safety has not been established.
-According to some authorities: This drug is only recommended for use during pregnancy when there are no safer alternatives and the benefit outweighs the risk.
AU TGA pregnancy category: B2
US FDA pregnancy category: Not assigned
Risk Summary: Based on findings in animals, this drug may cause fetal harm.
Comments:
-Animals exposed to this drug have shown negative developmental effects.
-Placental transfer of this drug and its metabolite have been reported.
-The available data on the use of this drug during pregnancy is limited and inconclusive. Pregnant women should be apprised of the potential risk to the fetus.
-This drug has been used widely for many years without apparent harmful effects.
-Infertility and impotence in men rarely occur during treatment with this drug, and studies have not confirmed an association with it.
Animal studies have failed to reveal evidence of fetotoxicity or teratogenicity. However, intraperitoneal administration of this drug in pregnant mice on gestation days 10 or 13 produced significant increases in fetal deaths and teratogenic effects (cleft palate, harelip, and digital defects). In another study, this drug after oral administration to pregnant rats during organogenesis caused embryonic resorptions, growth retardation, decreased fetal weight, and skeletal, liver, kidney, and brain abnormalities. A 2013 report analyzed 31 pregnancies exposed to this drug during the first trimester, finding that major birth defects and miscarriages were within the general population's range, but one child had severe defects. There is insufficient data in human pregnancy.
AU TGA pregnancy category B2: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.
US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.
References
- "Product Information. Allosig (allopurinol)." Arrow Pharma Pty Ltd 18 March 2025 (2025):
- "Product Information. Zyloric (allopurinol)." Aspen Pharma Trading Ltd 19 Feb 2025 (2025):
- "Product Information. Aloprim (allopurinol)." Mylan Institutional LLC 2/2022 (2022):
- "Product Information. Zyloprim (allopurinol)." Casper Pharma LLC 9/2023 (2023):
- "Product Information. Allopurinol (allopurinol)." Leading Pharma, LLC 9/2024 (2024):
Major
Metoprolol Succinate Er
+ Pregnancy
The following applies to the ingredients: Metoprolol (found in Metoprolol Succinate Er)
Professional Content
Safety has not been established during pregnancy.
-According to some authorities: Use is not recommended unless benefit outweighs risk; if used during pregnancy, administer the lowest possible dose and discontinue at least 2 to 3 days prior to expected delivery, if possible.
AU TGA pregnancy category: C
US FDA pregnancy category: Not assigned
Risk summary: Inconclusive data available on the use of this drug in pregnant women to inform a drug-related risk.
Comments:
-Based on published literature, this drug may cause erectile dysfunction and inhibit sperm motility.
Animal studies have revealed increased post-implantation loss, fetolethality, and decreased neonatal survival. This drug crosses placenta, neonates born to mothers who are receiving metoprolol during pregnancy, may be at risk for hypotension, hypoglycemia, bradycardia, and respiratory depression.
AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.
US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.
References
- "Product Information. Lopressor (metoprolol)." Novartis Pharmaceuticals PROD (2001):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
- "Product Information. Kapspargo Sprinkle (metoprolol)." Sun Pharmaceutical Industries (2023):
- "Product Information. Toprol-XL (metoprolol)." Melinta Therapeutics, Inc. (2023):
- "Product Information. Lopressor (metoprolol)." Validus Pharmaceuticals LLC (2025):
- "Product Information. Metoprolol Tartrate (metoprolol)." Hikma USA (formerly West-Ward Pharmaceutical Corporation) (2025):
Drug and Breastfeeding Interactions
Major
Allopurinol
+ Breastfeeding
The following applies to the ingredients: Allopurinol
Professional Content
Breastfeeding is not recommended during use of this drug and for 1 week after the last dose.
Excreted into human milk: Yes
Comments:
-This drug and its active metabolite were detected in human milk.
-There was no report of effects of this drug on the nursing infant or on milk production.
-If the mother requires this drug, she does not have to stop nursing, but the nursing infant should be monitored for allergic reactions (such as rash) and undergo periodic CBC and differential blood counts.
References
- Bethesda (MD): National Institute of Child Health and Human Development (US) "Allopurinol - Drugs and Lactation Database (LactMed) https://www.ncbi.nlm.nih.gov/books/NBK501198/" (2025):
- "Product Information. Allosig (allopurinol)." Arrow Pharma Pty Ltd 18 March 2025 (2025):
- "Product Information. Zyloric (allopurinol)." Aspen Pharma Trading Ltd 19 Feb 2025 (2025):
- "Product Information. Aloprim (allopurinol)." Mylan Institutional LLC 2/2022 (2022):
- "Product Information. Zyloprim (allopurinol)." Casper Pharma LLC 9/2023 (2023):
- "Product Information. Allopurinol (allopurinol)." Leading Pharma, LLC 9/2024 (2024):
Major
Metoprolol Succinate Er
+ Breastfeeding
The following applies to the ingredients: Metoprolol (found in Metoprolol Succinate Er)
Professional Content
AU and UK: Use is not recommended unless benefit outweighs risk.
US: This drug has been used without apparent harmful effects; caution is recommended.
Excreted into human milk: Yes (in small amounts)
Comments: This drug has been used without apparent harmful effects in the nursing infant.
An infant consuming 1 L of breast milk a day would receive a dose of less than 1 mg of drug.
References
- "Product Information. Lopressor (metoprolol)." Novartis Pharmaceuticals PROD (2001):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
Therapeutic Duplication Warnings
No warnings were found for your selected drugs.Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
Switch to: Professional Interactions
| Drug Interaction Classification | |
|---|---|
These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication. |
|
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
| Unknown | No interaction information available. |
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