While minor, some of these side effects may occur. They are as follows; Drowsiness, dizziness, lightheadedness, and weight gain may occur. Numbness/tingling of the mouth may also occur but usually goes away within 1 hour. Sores, blisters, or pain under the tongue may rarely occur. However if any of these persist or worsen, it’s best to speak with your doctor right away.
This drug may cause muscle/nervous system problems (extrapyramidal symptoms-EPS). Your doctor may prescribe another medication to decrease these side effects. Tell your doctor right away if you notice any of the following side effects: feelings of anxiety/agitation/jitteriness, drooling/trouble swallowing, restlessness/constant need to move, shaking (tremor), shuffling walk, stiff muscles, severe muscle spasms/cramping (such as twisting neck, arching back, eyes rolling up), mask-like expression of the face.
Infrequently, this medication may cause face/muscle twitching and uncontrollable movements (tardive dyskinesia). In some cases, this condition may be permanent. Tell your doctor right away if you develop any uncontrollable movements such as lip smacking, mouth puckering, tongue thrusting, chewing, or unusual arm/leg movements.
This drug may rarely make your blood sugar rise, which can cause or worsen diabetes. Weight gain from this drug may increase the risk of this side effect. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination. If you already have diabetes, check your blood sugar regularly as directed and share the results with your doctor. Your doctor may need to adjust your diabetes medication, exercise program, or diet.
In rare cases, asenapine may increase your level of a certain substance made by the body (prolactin). For females, this increase in prolactin may result in unwanted breast milk, missed/stopped periods, or difficulty becoming pregnant. For males, it may result in decreased sexual ability, inability to produce sperm, or enlarged breasts. If you develop any of these symptoms, tell your doctor right away.
Rarely, with similar drugs, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur.
Tell your doctor right away if you have any serious side effects, including: interrupted breathing during sleep (sleep apnea), signs of infection (such as fever, persistent sore throat).
Get medical help right away if you have any very serious side effects, including: severe dizziness, fainting, slow heartbeat, seizures.
This medication may rarely cause a very serious condition called neuroleptic malignant syndrome (NMS). Get medical help right away if you have any of the following symptoms: fever, muscle stiffness/pain/tenderness/weakness, severe tiredness, severe confusion, sweating, fast/irregular heartbeat, dark urine, signs of kidney problems (such as change in the amount of urine).
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.