Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Phyllocontin (Aminophylline). If you are concerned about side effects, discuss the risks and benefits of Phyllocontin (Aminophylline) with your doctor.

The following side effects have been reported by at least 1% of people taking Phyllocontin (Aminophylline). Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness
• headache
• irritability
• itching
• loss of appetite
• nausea
• rash
• restlessness
• trembling
• trouble sleeping
• unusual tiredness or weakness
• upset stomach

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if the following side effects occur:

• irregular heartbeat
• rapid, pounding heartbeat
• vomiting

Stop taking the medication and seek immediate medical attention if any of the following occur:

• confusion or change in behaviour
• convulsions (seizures)
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of bleeding in the stomach (e.g., bloody, black, or tarry stools, spitting up of blood, vomiting blood or material that looks like coffee grounds)
• signs of having taken too much theophylline (e.g., hearing changes, vision changes, unusually fast breathing or heartbeat, headache, Fever, flushing, extreme thirst, change in urination)
• nervousness or restlessness (continuing)
• trembling (continuing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Phyllocontin (Aminophylline).

Do not take Phyllocontin (Aminophylline) if you:

• are allergic to theophylline, any of the xanthines, or any ingredients of the medication
• have Coronary Artery Disease (when, in the opinion of the doctor, it would be harmful to stimulate the heart)
• have peptic ulcers
• are taking ephedrine and are a child

There may be an interaction between theophylline sustained release and any of the following:

• Abiraterone
• acyclovir
• Adalimumab
• alcohol
• Allopurinol
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, Lisdexamfetamine)
• Atomoxetine
• barbiturates (e.g., butalbital, pentobarbital, Phenobarbital,)
• benzodiazepines (e.g., Diazepam, Lorazepam)
• beta-adrenergic blockers (e.g., Atenolol, Propranolol, Sotalol, Timolol)
• birth control medications
• bronchodilators: fast-acting (e.g., salbutamol, terbutaline) and long-acting (e.g., formoterol, Indacaterol, salmeterol)
• caffeine
• cannabis
• Carbamazepine
• Cimetidine
• Cyproterone
• decongestant cold medications (e.g., phenylephrine, Pseudoephedrine)
• decongestant eye drops and nose sprays (e.g., naphazoline, oxymetazoline, xylometazoline)
• Deferasirox
• Digoxin
• dipivefrin
• disulfiram
• dobutamine
• Epinephrine
• estrogens (e.g., conjugated estrogen, Estradiol, ethinyl estradiol)
• Febuxostat
• Fluvoxamine
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• Influenza vaccine
• interferon
• isoniazid
• Linezolid
• lithium
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• Methimazole
• Methotrexate
• Methylphenidate
• Mexiletine
• Modafinil
• Nabilone
• nondepolarizing muscle relaxants (e.g., pancuronium, atracurium)
• norepinephrine
• Pentoxifylline
• Phenytoin
• Propafenone
• Propylthiouracil
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, Ofloxacin, Norfloxacin)
• Riociguat
• Roflumilast
• St. John's wort
• selective serotonin reuptake inhibitors (SSRIs; e.g., fluvoxamine, Fluoxetine, Paroxetine)
• simeprevir
• Stiripentol
• Sulfinpyrazone
• thyroid hormones (e.g., Levothyroxine, Liothyronine, thyroid)
• Ticlopidine
• tyrosine kinase inhibitors (e.g., Crizotinib, Dabrafenib, imatinib)
• Vemurafenib
• Warfarin
• Zafirlukast

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Phyllocontin (Aminophylline). Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use Phyllocontin (Aminophylline).

Cystic Fibrosis: People with cystic fibrosis break theophylline down more quickly than people without cystic fibrosis. If you have cystic fibrosis, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Heart disease: For people with certain types of heart disease, such as Congestive Heart Failure, theophylline may build up in the body and cause side effects. If you have heart disease, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Heart rhythm: Phyllocontin (Aminophylline) can cause an irregular heartbeat or make an irregular heartbeat worse. If you have a history of irregular heartbeat (arrhythmia), discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Kidney function: Kidney Disease or reduced kidney function may cause Phyllocontin (Aminophylline) to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Laboratory tests: There a small difference between the amount of theophylline in your body that makes it an effective medication and the amount that makes it toxic. Your doctor may ask you to have your blood tested to check your blood levels of theophylline. It is very important to keep these appointments, to make sure that you are not receiving too much medication.

Liver function: Liver disease or reduced liver function may cause Phyllocontin (Aminophylline) to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking Phyllocontin (Aminophylline).

Medical conditions: Any of the following medical conditions can affect how theophylline is processed and used by your body (metabolized): fever or viral infections, low oxygen levels, high blood pressure, a known or suspected ulcer, acute pulmonary edema, pneumonia, severe fever, COPD (Chronic Obstructive Pulmonary Disease), impaired kidney function, or following a high-carbohydrate and low-protein diet. Some of these conditions may also be affected by theophylline. If you have any of these medical conditions, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Overdose: An overdose may lead to serious side effects such as racing heart rate, abnormal heart rate, and seizures. It is important to take the medication exactly as prescribed by your doctor. From time to time, your doctor may ask you to have your blood tested to check your blood levels of theophylline.

Seizures: Theophylline may cause an increase in the number or length of seizures for people who have a medical history that includes seizures. If you have a history of Epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how Phyllocontin (Aminophylline) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phyllocontin (Aminophylline), and whether any special monitoring is needed.

Smoking: Tobacco smoking causes your body to process theophylline faster than if you were a non-smoker. If you are a smoker and quit smoking, inform your doctor, as your dose may need to be adjusted. Likewise, if you start smoking while you are taking theophylline, you should also let your doctor know.

Thyroid disease: People with an underactive thyroid gland are more likely to experience side effects of theophylline because the medication may build up in the body. People with an overactive thyroid gland may clear theophylline from the body too quickly for it to be very effective. In both cases, it is important to have blood tests done when your doctor orders them, to make sure you are getting the right amount of medication to treat your illness.

Pregnancy: Phyllocontin (Aminophylline) should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Phyllocontin (Aminophylline), contact your doctor immediately.

Breast-feeding: Phyllocontin (Aminophylline) passes into breast milk. If you are a breast-feeding mother and are taking theophylline, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: Children are very sensitive to theophylline, as the margin of safety above therapeutic doses is small. Phyllocontin (Aminophylline) is not recommended for children under 12 years of age, as proper dosages for this age group have not been established.

Seniors: Seniors may be more likely to experience side effects and high levels of theophylline in the blood due to the body's decreased ability to clear Phyllocontin (Aminophylline).