7 Interactions found for:
Drug Interactions
No drug interactions were found for selected drugs: allopurinol, Tylenol.
This does not necessarily mean no interactions exist. Always consult your healthcare provider.
Drug and Food Interactions
Major
Tylenol
+ Food
The following applies to the ingredients: Acetaminophen (found in Tylenol)
Ask your doctor before using acetaminophen together with ethanol. This can cause serious side effects that affect your liver. Call your doctor immediately if you experience a fever, chills, joint pain or swelling, excessive tiredness or weakness, unusual bleeding or bruising, skin rash or itching, loss of appetite, nausea, vomiting, or yellowing of the skin or the whites of your eyes. If your doctor does prescribe these medications together, you may need a dose adjustment or special tests to safely take 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.
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
Tylenol
+ Food
The following applies to the ingredients: Acetaminophen (found in Tylenol)
Professional Content
MONITOR: Smoking cessation may lead to elevated plasma concentrations and enhanced pharmacologic effects of drugs that are substrates of CYP450 1A2 (and possibly CYP450 1A1) and/or certain drugs with a narrow therapeutic index (e.g., flecainide, pentazocine). One proposed mechanism is related to the loss of CYP450 1A2 and 1A1 induction by polycyclic aromatic hydrocarbons in tobacco smoke; when smoking cessation agents are initiated and smoking stops, the metabolism of certain drugs may decrease leading to increased plasma concentrations. The mechanism by which smoking cessation affects narrow therapeutic index drugs that are not known substrates of CYP450 1A2 or 1A1 is unknown. The clinical significance of this interaction is unknown as clinical data are lacking.
MANAGEMENT: Until more information is available, caution is advisable if smoking cessation agents are used concomitantly with drugs that are substrates of CYP450 1A2 or 1A1 and/or those with a narrow therapeutic range. Patients receiving smoking cessation agents may require periodic dose adjustments and closer clinical and laboratory monitoring of medications that are substrates of CYP450 1A2 or 1A1.
References
- "Product Information. Cytisine (cytisinicline)." Consilient Health Ltd (2024):
- jeong sh, Newcombe D, sheridan j, Tingle M "Pharmacokinetics of cytisine, an a4 b2 nicotinic receptor partial agonist, in healthy smokers following a single dose." Drug Test Anal 7 (2015): 475-82
- Vaughan DP, Beckett AH, Robbie DS "The influence of smoking on the intersubject variation in pentazocine elimination." Br J Clin Pharmacol 3 (1976): 279-83
- Zevin S, Benowitz NL "Drug interactions with tobacco smoking: an update" Clin Pharmacokinet 36 (1999): 425-38
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):
Minor
Tylenol
+ Pregnancy
The following applies to the ingredients: Acetaminophen (found in Tylenol)
Professional Content
Benefit should outweigh risk
AU TGA pregnancy category: A
US FDA pregnancy category: Not Assigned
Risk Summary: A clear association of drug use and birth defects, miscarriage, or adverse maternal or fetal outcomes has not been shown with human use; animal studies have demonstrated adverse events at clinically relevant doses.
In pregnant rats receiving oral drug at doses up to 0.85 times maximum human daily dose (MHDD) during organogenesis, fetotoxicity and dose-related increases in bone variations (reduced ossification and rudimentary rib changes) were observed. Areas of necrosis in both the liver and kidney of pregnant rats and fetuses were observed when pregnant rats were given oral drug throughout gestation at doses 1.2 times the maximum human daily dose. Animal studies using the IV formulation have not been performed. In humans, this drug and its metabolites cross the placental barrier. Large cohort studies have not found an association between maternal use in the first trimester and either adverse pregnancy outcomes or congenital malformations. Some evidence of increased risk of neurodevelopmental disorders (e.g., attention deficit hyperactivity disorder [ADHD]), respiratory illness (e.g., asthma) and reproductive toxicity (e.g., androgen disruption) has been suggested in epidemiologic studies. However, extrapolating causation from pharmaco-epidemiological studies to humans is tricky considering various confounders and biases inherent in the study design. Associations seen in clinical cohort studies need clarification with randomized clinical trials (RCTs), which would be difficult to perform ethically in pregnant populations. The mechanism by which this drug or its metabolites affect neurological development, asthma, or endocrine/reproductive toxicity is poorly understood. It is important to factor in the risk of untreated febrile illness in mother and child when evaluating risks and benefits of using this drug. There are no controlled data in human pregnancy.
Epidemiologic data, including a population based case-control study from the National Birth Defects Prevention Study (n= 11,610) and data from 26,424 live singleton births have shown no increased risk of major birth defects in children with first trimester prenatal exposure. In 2015, the US Food and Drug Administration released results of their evaluation on published research studies looking at mothers who took this drug as either an over the counter or prescription product at any time during their pregnancy and the risk of attention deficit hyperactivity (ADHD) in their babies. They found all studies reviewed had potential limitations in their designs that prevented drawing reliable conclusions. In a prospective birth cohort study (Avon Longitudinal Study or Parents and Children [ALSPAC]) maternal drug exposure was assessed by questionnaire at 18 and 32 weeks, children were assessed at 61 months. Mothers were questioned about behavioral problems in their children at 7 years old; children's behavioral problems were assessed using the Strengths and Difficulties Questionnaire (SDQ). A number of confounders were evaluated although a limitation of the study was lack of information for drug use. The authors suggest there may be an association between drug use during pregnancy and behavioral problems in childhood that may be due to an intrauterine mechanism. Further studies are needed to test alternatives to a causal explanation.
According to published animal studies, this drug may cause reduced fertility in both males and females described as decreased testicular weights, reduced spermatogenesis, reduced fertility; and reduced implantation sites, respectively.
AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
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
- Cerner Multum, Inc. "Australian Product Information." O 0
- U.S. Food and Drug Administration U.S. Food and Drug Administration U.S. Food and Drug Administration U.S. Food and Drug Administration "FDA Drug Safety Communication: FDA has reviewed possible risks of pain medicine use during pregnancy http://www.fda.gov/Drugs/DrugSafety/ucm429117.htm" (2015):
- "Product Information. Ofirmev (acetaminophen)." Cadence Pharmaceuticals Inc (2016):
- Stergaikoulie E, Thapar A, Davey Smith G "Association of acetaminophen use during pregnancy with behavioral problems in childhood: evidence against confounding." JAMA Pediatr 170 (2016): 964-70
- McCrae JC, Morrison EE, MacIntyre IM, Dear JW, Webb DJ "Long-term adverse effects of paracetamol - a review." Br J Clin Pharmacol 84 (2018): 2218-2230
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):
Minor
Tylenol
+ Breastfeeding
The following applies to the ingredients: Acetaminophen (found in Tylenol)
Professional Content
Caution is recommended.
Excreted into human milk: Yes
Comments;
-This drug has been used without apparent harmful effects.
-This drug is considered compatible with breastfeeding by the American Academy of Pediatrics.
This drug is excreted into breast milk in very small amounts. Published reports reveal peak levels occur 1 to 2 hours after dosing and are undetectable after 12 hours. Reports have also shown infants ingesting 90 mL of breast milk every 3 hours would receive an average of 0.14% (range 0.04% to 0.23%) of the mother's dose; calculated to be a maximum maternal weight-adjusted dose of around 2%. Other studies have shown similar calculated maximal maternal weight adjusted doses (1.1% to 3.6%); these doses are about 0.5% of the lowest recommended infant dose of this drug. A single case of a maculopapular rash has been reported in a 2-month old nursing infant; the rash recurred on rechallenge.
References
- Committee on Drugs, 1992 to 1993 "The transfer of drugs and other chemicals into human milk." Pediatrics 93 (1994): 137-50
- Cerner Multum, Inc. "Australian Product Information." O 0
- United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):
- "Product Information. Ofirmev (acetaminophen)." Cadence Pharmaceuticals Inc (2016):
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 | |
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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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