Adverse effects most frequently occur at the start of treatment (e.g., sedation, somnolence), particularly if the dosage is increased too rapidly, if large doses are administered, and in the elderly patient. However, these effects are often transient and can be alleviated or eliminated by decreasing the dosage; they are seldom severe enough to warrant withdrawal of the medication.
Should persistent nausea occur following a reduction in dosage, it is recommended that pms-BACLOFEN be ingested with food or a milk beverage.
Lowering of the convulsion threshold and convulsions may occur, particularly in epileptic patients.
In elderly patients or those patients with cerebrovascular disorder or a history of psychiatric illness, more serious adverse reactions may occur, such as hallucinations and confusion.
Muscular hypotonia of a degree sufficient to make walking or movement difficult may occur, but is usually relieved by readjusting the dosage. For this purpose, the overall dose of pms-BACLOFEN may be reduced, or the daytime dose reduced and the evening dose increased.
Certain patients have shown increased muscle spasticity as a paradoxical reaction to the medication.
Some of the CNS and genitourinary symptoms reported may be related to the underlying disease rather than to drug therapy.
Adverse reactions listed as follows are ranked using the following convention: very common (≥ 1/10); common (≥ 1/100, < 1/10); uncommon (≥ 1/1,000, < 1/100); rare (≥ 1/10,000, < 1/1,000); very rare (< 1/10,000); not known (cannot be estimated from the available data).
The most common adverse reactions associated with baclofen are transient somnolence, sedation, dizziness, weakness and fatigue. Other adverse reactions reported were: Nervous System Disorders: Common: Headache, insomnia, muscular weakness, tremor, ataxia, respiratory depression, euphoric mood, depression, confusional state, hallucinations, nightmare, myalgia, nystagmus, and dry mouth.
Rare: Excitement, paresthesia, tinnitus, slurred speech, coordination disorder, rigidity, dystonia, dysarthria, epileptic seizures, lowered convulsion threshold, and dysgeusia.
Eye Disorders: Common: Accommodation disorders, visual impairment.
Rare: Blurred vision, strabismus, miosis, mydriasis, diplopia.
Cardiac Disorders: Common: Cardiac output decreased.
Rare: dyspnea, palpitation, chest pain, syncope.
Not known: Bradycardia.
Vascular Disorders: Common: Hypotension.
Gastrointestinal Disorders: Very common: Nausea.
Common: Constipation, gastrointestinal disorders, retching, vomiting, diarrhea.
Rare: Anorexia, abdominal pain, and positive test for occult blood in stool.
Hepatobiliary Disorders: Rare: Hepatic function abnormal.
Skin and Subcutaneous Tissue Disorders: Common: Instances of rash, hyperhidrosis, pruritus.
Not known: Urticaria.
Renal and Urinary Disorders: Common: Pollakiuria, enuresis, dysuria.
Rare: Nocturia, hematuria, urinary retention.
Reproductive System and Breast Disorders: Rare: Erectile dysfunction, inability to ejaculate.
General Disorders and Administration Site Conditions: Common: Fatigue, ankle edema.
Very rare: Hypothermia.
Not known: Drug withdrawal syndrome*.
Investigation: Not known: Blood glucose increased.
Other: Weight gain, nasal congestion.
*Drug withdrawal syndrome including, irritability, high-pitched crying, tremor, hypertonicity, excessive sucking, disordered sleep, hyperthermia, mottling, and postnatal convulsions has also been reported after intra-uterine exposure to oral baclofen.