血小板过多症即血中血小板计数超过四十万称之，临床诊断分为两大类：

一、反应性血小板过多症，亦称续发性血小板过多症（secondary thrombcytosis）。
二、原发性血小板增多症（primary thrombocytosis），临床多属绩发性者，约佔87%病例，其病因顺序包括组织伤害（tissue tauma）、感染（infection）、肿瘤（malignancy）及慢性炎症（chronic inflammation）。
百分之十的临床病童有反应性血小板增多症，其中百分之七十五因感染所导致，以肺炎、胃肠炎及横川氏症（Kawasaki’s disease）引起者最多件。续发性血小板增多程度与病因有关，於发病四日内见血小板增高，往往介乎六十至百万之间，增多症随病因去除而缓和，通常在一至三週内恢復正常，由於续发性血小板增多为时短暂，多不致发生栓塞或出血等併发症，故良性血小板增多症绝无需治疗之必要。但对有特殊危险因子的患者应小心处理，包括有消化性溃疡出血、脑血管疾病、心肌梗塞病史的病患。原发性血小板过多症属骨髓异常增生性疾病（myeloproliferative disease）的一种，平均发病年龄为55岁，偶发於年轻患者，骨髓增生性疾病除原发性血小板过多症外（essential thrombocythemia），尚包括多血症（polytcythemia vera）、慢性骨髓球白血病（chronic myelocytic leukemia）、骨髓纤维化（agnogenic myeloid metaplasia or idiopathic myelofibrosis，AMM），致病机制在於造血干细胞促族群异常，导致过度增生现象，临床表现循环血球过多跡象，包括红血球、白血球、血小板三类血球，可產生高代谢率症候群，常有疲劳、低烧、食慾不振、体重下降、腹胀等症状，亦会有脾臟肿大、微血管栓塞或出血现象。
此等骨髓增生性疾病中因原发性血小板过多症只有血小板异常表现，通常预后极佳，死亡率极低，但有百分之五的患者发生异常出血，约五分之一的患者有栓塞症状，其中脑血管疾病，急性心肌梗塞可致命，因此目前治疗原则为使用化学治疗或放射性同位素以压制骨髓细胞增殖，放射性磷、hydroxyurea、干扰素（IFN-a）、busulfan、melphalan是常用的药物，但此等药物纵然能抑制各类血液细胞的增殖，但有各类的副作用，如hydroxyurea、busulfan、melphala可导致皮肤色素沉著、皮肤溃疡、肺臟纤维化，更甚者是会引发续发癌，使用达十年以上者有百分之十发生急性白血病的危险性。干扰素虽无明显致癌的可能，但疗效慢，治疗期间严重影响病患的生活品质，包括发热、疲乏、食慾不振、冷颤、肌肉疼痛、昏眩等，此类药品用以治疗原发性血小板过多症时最困扰者莫过於会同时导致白血球及红血球的减少，產生诸多的併发症，治疗医师常遭遇血小板仍处过高状态，但因白血球过低而被迫暂停治疗。

此种情况自1997年三月美国通过临床使用一种有选择性降血小板的药剂后得以改善，此药名称为Agrylin安归宁，主要成分是anagrelide hydrochloride，原有抑制血小板凝集的作用，有抗血栓效果，但以低剂量处方时则意外发现有降低血小板数的功效，主要是减慢骨髓内血小板母细胞（megakaryocyte）分化成熟度，使血小板產量减少，但并非影响血小板母细胞的分裂增殖，对DNA、RNA无伤害，故不会有致癌性，其可抗血小板凝集作用则间接因为减少血小板產生cAMP（cyclic adenosine monophosphate）之故，但其作用所需剂量约为降低血小板数剂量的十倍以上，安归宁目前以口服啶剂问世，最适合需长期治疗的门诊病患，用以治疗原发性血小板过多症无白血球降低及引起贫血之虞，但其心臟血管效应则会有头痛、心悸、眩晕、水肿、呕心、腹痛、腹泻、胸痛等副作用，此心臟血管副作用有种别差异，动物试验中并无此效应，再次反应新药临床试验的重要性，其中以头痛发生率最高达四成五，多在开始用药的前二週内发生可以scanol缓和症状，副作用多再二週后慢慢消失但有三分之一的患者会因副作用而须暂停用药，用以治疗有心臟疾病的病患应特别小心，药物经肝臟代谢尿液中排出，故肝肾功能异常的患者亦须审慎处方。
目前上市的啶剂分别有0.5毫克1毫克，起始每日剂量为二毫克可以0.5毫克啶分四次给予或1毫克两次服用，逐渐调剂至血小板数降至六十万以下或栓塞出血症状消失，每日递增剂量已0.5毫克为限，每日最高剂量不得超过十毫克，每次口服剂量应在2.5毫克以下，通常每日有效剂量为1.5至3毫克，服药后约7日血小板开始下降，百分之七十病患可获满意疗效，其餘百分之十患者可部分缓解，临床试验显示纵使对hydroxyurea治疗效果不佳的病患对安归宁亦有良好疗效，多在服药后二至四周达到完全疗效其后可递减至维持剂量，可长期使用因无致癌的危险性，特别适用於年轻的患者，但可穿越胎盘不可使用於怀孕的妇女，高雄荣总血液肿瘤科目前共发现七名年龄低於三十岁的原发性血小板过多症患者，男性居多共六男一女，最低年龄13岁诊断时血小板计数自八十万至一百五十五万，脾臟略肿大或正常皆无临床栓塞出血现象，血小板超过百万者皆接受hydroxyurea治疗，无短期副作用，但新药安归宁的问世肯定是此些年轻患者的福音。

通用名称：阿那格雷

英文名称：Anagrelide

中文别名：氯喹咪唑酮、盐酸阿那格利

英文别名：Agrylin、Anagrelide Hydrochloride

【适应症】
1.Anagrelide lowers the number of blood clotting cells (called platelets) in the body. This helps to prevent blood clots from forming.
2.Anagrelide is used to treat essential thrombocytosis (too many blood clotting cells in the body).
3.Anagrelide may also be used for purposes other than those listed in this medication guide.
【用法用量】
1.Take anagrelide exactly as directed by your doctor. If you do not understand these instructions, ask your pharmacist, nurse, or doctor to explain them to you.
2.Take each dose with a full glass of water.
3.Your doctor will need to monitor your blood with blood tests before starting treatment with anagrelide, every 2 days for the first week of treatment, and at least weekly thereafter until the desired maintenance dosage is reached.
4.Store anagrelide at room temperature away from moisture and heat.
【注意事项】
1.Your doctor will need to monitor your blood with blood tests before starting treatment with anagrelide, every 2 days for the first week of treatment, and at least weekly thereafter until the desired maintenance dosage is reached.
2.Tell your doctor and dentist that you are taking this medication before undergoing any surgical procedures.
If Miss a Dose: 1.Take the missed dose as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and take only your next regularly scheduled dose. Do not take a double dose of this medication.
Contraindications: 1.Before taking anagrelide, tell your doctor if you have
* heart disease,
*kidney disease, or
*liver disease.
2.You may not be able to take anagrelide, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.
3.Anagrelide is in the FDA pregnancy category C. This means that it is not known whether it will harm an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant.
4.It is not known whether anagrelide passes into breast milk. Do not take this medication without first talking to your doctor if you are breast feeding a baby.
5.Anagrelide is not approved for use by children younger than 16 years old.
Special Concerns: 1.Tell your doctor and dentist that you are taking this medication before undergoing any surgical procedures.
【不良反应】
1.If you experience any of the following serious side effects, stop taking anagrelide and seek emergency medical attention or notify your doctor immediately:
*an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
*fast, slow, or irregular heartbeat;
*chest pain;
*swelling of the hands, feet, or legs;
*shortness of breath or difficulty in breathing;
*seizures;
*bloody or black vomit or stools;
*abdominal pain;
*unusual, prolonged, or severe bleeding or bruising; or
*a bleeding nose.
2.Other, less serious side effects may also occur. Continue to take anagrelide and talk to your doctor if you experience
*headache;
*diarrhea;
*tingling or numbness in the hands or feet;
*upset stomach, nausea, or vomiting;
*dizziness;
*gas;
*fever;
*a rash or itching;
*loss of appetite;
*sore throat;
*cough; or
*back pain.
3.Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.
【相互作用】
1.There are no known interactions between anagrelide and other medicines. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines.
【药物过量】
1.Seek emergency medical attention.
2.Symptoms of a anagrelide overdose are unknown but might include bleeding and blood in the vomit or stool.