Levbid (Hyoscyamine)
Anaspaz®, Cystospaz®, Cystospaz-M®, Gastrosed®, Levbid®, Levsin®, Levsinex®, NuLev®, Symax™ Duotabs, Symax™ SR | A-Spas™ S/L | Colidrops® | Colytrol™ Drops | Hyco® | Hyosol® SL | Hyospaz® | Hyosyne™ | IB Stat™ | Levsin® SL | Losamine™ | Medispaz™ | Neosol™ | Spacol® Liquid | Spasdel™ | Symax™ SL | Symax® FasTabs™
Classification:
Autonomic Agents
Gastrointestinal Agents
Genitourinary Agents
Respiratory Agents
Description: L-Hyoscyamine is an oral and parenteral tertiary amine anticholinergic gastrointestinal agent. It is one of the optical isomers of atropine (dl-hyoscyamine). L hyoscyamine possesses all of the antimuscarinic activity; d-hyoscyamine essentially has no peripheral antimuscarinic activity. Hyoscyamine has been used as adjunct therapy in the management of peptic ulcer disease, hypermotility disorders of the lower urinary tract, infant colic, and as a preoperative medication to control salivation and excessive secretions. As with other antimuscarinic agents, there are no conclusive data from well-controlled studies that indicate that hyoscyamine aids in the healing, decreases the rate of occurrence, or prevents complications of peptic ulcers; more effective agents are available. Other indications for which hyoscyamine is FDA approved but have been replaced by more effective agents include biliary tract disorders, cystitis, and severe allergic rhinitis. Hyoscyamine has been available since before 1938. An orally disintegrating tablet was approved July 2000.
Mechanism of Action: Hyoscyamine is a competitive inhibitor at autonomic postganglionic cholinergic receptors. These include receptors found in gastrointestinal and pulmonary smooth muscle, exocrine glands, the heart, and the eye. L-hyoscyamine does not block the actions of acetylcholine at the neuromuscular junction. The degree of sensitivity of various muscarinic receptors to antimuscarinic agents is dose-dependent. The most sensitive receptors are those of the salivary, bronchial, and sweat glands. Next are the receptors in the eye and heart, followed by the receptors in the gastrointestinal tract.
The principal clinical effects of l-hyoscyamine are a reduction in salivary, bronchial, and sweat gland secretions; mydriasis; cycloplegia; changes in heart rate; contraction of the bladder detrusor muscle and of the gastrointestinal smooth muscle; decreased gastric secretion; and decreased gastrointestinal motility. At lower doses, a paradoxical decrease in heart rate occurs, and at higher doses, effects are seen at nicotinic receptors in autonomic ganglia, causing restlessness, hallucinations, disorientation, and/or delirium. Unlike scopolamine, l-hyoscyamine does not produce CNS depression (drowsiness, euphoria, amnesia, fatigue, decreased REM sleep) at usual therapeutic doses. Also, l-hyoscyamine’s antimuscarinic potency is greater in the heart, bronchial, and gastrointestinal smooth muscle, and is lesser in the iris; ciliary body; and salivary, sweat, and bronchial glands.
The respiratory effects of l-hyoscyamine include reducing the volume of secretions from the nose, mouth, pharynx, and bronchi and relaxing smooth muscles of the bronchi and bronchioles, which decrease airway resistance. Since l-hyoscyamine is a potent bronchodilator, it is especially effective in blocking the acetylcholine-induced stimulation of guanyl cyclase, which is responsible for producing cyclic guanosine monophosphate (cGMP), a mediator of bronchoconstriction released from mast cells. These actions of l-hyoscyamine are useful, but controversial, in the treatment of antigen-, methacholine-, and exercise-induced bronchospasm in asthmatic patients.
Pharmacokinetics: Hyoscyamine is administered orally. Hyoscyamine sulfate is administered orally, sublingually, or parenterally. Following oral administration, hyoscyamine is well absorbed from the gastrointestinal tract. Food does not affect absorption. Extended release formulations deliver hyoscyamine at a rate of approximately 0.125 mg/4 hours. The relative bioavailability from extended-release capsules was reported to be about 43% that of the conventional tablets. The relative bioavailability from extended-release tablets was reported to be about 92% that of the conventional tablets. The onset of action is about 20-30 minutes after administration of conventional tablets. When the conventional tablets are chewed or administered sublingually or when administered orally as an elixir or solution, the onset of action is 5-20 minutes; peak pharmacologic effects occur within 30-60 minutes and lasts for about 4 hours. After administration of hyoscyamine sulfate extended-release capsules or tablets, the drug has an onset of action of about 20-30 minutes; pharmacologic effects peak within 40-90 minutes and persists for about 12 hours. Parenteral administration of hyoscyamine sulfate results in an onset of action of 2-3 minutes with peak pharmacologic effects occurring within 15-30 minutes and persisting for up to 4 hours.
Once in the systemic circulation, hyoscyamine is well distributed throughout the body. The drug crosses the blood-brain barrier and small amounts distribute into milk and can be found in placental tissues. Protein binding is about 50%. Hyoscyamine is metabolized in the liver to tropic acid, tropine, and hyoscyamine glucuronide. Excretion occurs in the urine primarily as unchanged drug (approximately 30-50%) and metabolites. The elimination half-life in patients with normal renal function is about 3.5 hours; elimination is prolonged in patients with impaired renal function.
[1 of 20 - Click here to see more photos]
[ Revised 5/20/2005 2:14:00 PM ]
Related entries
Syndicate
|
